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1 NOTE CAREFULLY The following document was developed by Learning Materials Production, OTEN, DET. Adaptation of this material requires the observation of moral rights obligations regarding attributions to source and author. For example: This material was adapted from (Title of LMP material) produced by Learning Materials Production, OTEN. Furthermore, this material contains 3 rd party copyright items which limits the way it can be used. To clarify which items are 3 rd party copyright, contact the CLI Copyright Unit on (02) For further information about the use of the DET copyright licences under Part VB of the Copyright Act 1968 see: Use of the 3 rd party copyright elements in this material should comply with conditions of the CAL (Copyright Agency Limited) Electronic Reproduction and Communication Licence. Please read and observe the following: USE OF 3RD PARTY MATERIIAL ON E--MEDIIA UNDER THE CAL LIICENCES Material may be communicated for the purposes of NSW DET on CD ROM/Intranet providing the terms and conditions of the Copyright Agency Limited [CAL] Electronic Reproduction and Communication Licence and the Education Hardcopy Licence are followed. Material containing third party copyright items produced under the licences may not be sold for profit under this scheme. Teachers may tailor materials for their own students but may not interfere with the integrity of third party copyright materials or their accompanying citation. It is a legal requirement that the moral rights of creators of these works is respected. The following principles must be observed with regard to 3 rd party copyright elements: Warn The Commonwealth Government Warning Notice below must appear at the head of any adaptation that includes 3 rd party copyright items communicated electronically. This notice does not have to be included when the materials are printed. Observe Observe CAL limits. Items must comply with the CAL limits which are different under the electronic use notice compared to the provisions under the hardcopy licence. Full details of the guidelines entitled Copying rights for educational institutions can be found at:

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5 Gill Sans Bold Senior Science HSC Course Stage 6 Lifestyle chemistry IncorporatingOctober2002 AMENDMENTS SSCHSC43168 P

6 Acknowledgments This publication is copyright Learning Materials Production, Open Training and Education Network Distance Education, NSW Department of Education and Training, however it may contain material from other sources which is not owned by Learning Materials Production. Learning Materials Production would like to acknowledge the following people and organisations whose material has been used. Senior Science Syllabus Stage 6 Board of Studies NSW, Amended October 2002 The most up-to-date version is to be found at Garnett, P Foundations of Chemistry. Pearson Education Australia. Noble, W The Skin Microflora and Microbial Disease. Cambridge University Press. Victoria. Australia. Tannock, G Normal Microflora. Chapman and Hall. London. Laidler, G Environmental Chemistry an Australian Perspective 2 nd Edition. Pearson Education Australia Chemical Fact Sheets. ICI Australia. Melbourne. Orion Laboratories Pty Ltd. Western Australia. Material safety data sheets. < > (accessed 4 July 2000). To complete this module you will need to access: audio recordings either by using the audiotape Skin or using the internet to access the Skin audio files at go to Senior Science, go to Lifestyle Chemistry ph paper All reasonable efforts have been made to obtain copyright permissions. All claims will be settled in good faith. Writer: Editor: Consultant: Illustrator: Revised: Shelly Hudson Julie Haeusler Jenny Glen Thomas Brown Richard Alliband Copyright in this material is reserved to the Crown in the right of the State of New South Wales. Reproduction or transmittal in whole, or in part, other than in accordance with provisions of the Copyright Act, is prohibited without the written authority of Learning Materials Production. Learning Materials Production, Open Training and Education Network Distance Education, NSW Department of Education and Training, 2000 Revised October Wentworth Rd. Strathfield NSW 2135.

7 Contents Module overview...ii Resources... iii Icons...v Glossary... vi Part 1: The substances you use Part 2: Mixing it up Part 3: Your skin Part 4: What s growing on your skin? Part 5: Dissolve it! Part 6: Good medicine Student evaluation of module Introduction i

8 Module overview Welcome to the Lifestyle chemistry module for the HSC component of the Senior Science course. If you have ever wondered why some soaps, detergents of cleansers work better than others then this module will help answer your queries. You will first study the common substances you use and identify them as solutions, suspensions or colloids. You might be surprised to find that many of the substances you use daily are a type of colloid. You will be involved in the kitchen preparing some tasty foods that are classified as suspensions and colloids. This module will enable you to more easily understand the chemistry behind your soaps and detergents based on their ingredients. As you learn about the properties of water and alcohol as solvents, you will inspect the labels of common substances in the home for their ingredients and the solvents used in them. You will even better understand the chemistry behind substances that feel warm or cool on your skin. Despite the use of soaps and detergents you have microbes that live on your skin. You will understand their role and natural skin acidity in protecting you against disease through an audiotape or internet audio files from the web site. You will test the ph of a range of skin and hair products. You will be asked to test the manufacturer s claims of a skin or hair product. You might choose to test different shampoos for claims of improved body or shine. This experiment will take the form of an open-ended investigation. Lastly, you will appreciate different forms of medication such as capsules, enteric coated and slow release tablets and implants placed under the skin and relate these to the solubility of the drugs involved. Enjoy Lifestyle chemistry. Be aware you may find yourself explaining to people why substances and medications work. ii Lifestyle Chemistry

9 Resources You will need the following equipment to carry out activities and experiments during the module. In most cases, you should have most of the items listed around your home. If not, some items can be made easily, with little expense. Part 1 scissors glue sugar coffee salt milk ingredients and equipment to make: meringues salad dressing mayonnaise flour soil teaspoon two glasses or transparent cups funnel pen-sized laser pointer OR a torch with scissors, cardboard and rubber band filter paper / paper towel / coffee filters from a supermarket cook books common substances found in the home Introduction iii

10 Part 2 pin or paper clip three waxy leaves toothpicks a packet of jelly snakes a packet of jelly beans or another type of jelly lolly detergent oil small jar Part 3 Skin audiotape and tape player or access to Skin audio files shampoo label soap label cleanser label light microscope (optional) prepared slide of a skin cross section (optional) Part 4 20 cm length of universal ph paper (supplied by teacher) coloured pencils eight skin and/or hair products eight cotton buds or ice cream sticks Part 5 six cosmetics and/or medications for external use from home Part 6 vitamin pills label a variety of drug forms capsules, tablets, enteric coated tablets, slow-release tablets transparent containers iv Lifestyle Chemistry

11 Icons The following icons are used within this module. The meaning of each is written beside it: The hand icon means there is an activity for you to do. It may be an experiment or you may make something. The talk icon guides you to discuss a topic with others. There are exercises at the end of each part for you to complete and send to your teacher. The headphone icon asks you to complete an activity while listening to an audio file. The safety glass icon points out that care needs to be taken when carrying out a task. There are suggested answers for the following questions at the end of each part. Introduction v

12 Glossary The following glossary provides the scientific meaning for many of the term used in this module, Lifestyle chemistry. The HSC examiner will expect you to understand the meaning of every scientific term used. If you find a term that you do not understand, then look it up in a scientific dictionary or ask your teacher for assistance. acid substance capable of forming hydrogen ions when dissolved in water; substance with a ph below 7 acid mantle the slightly acid ph of skin, protecting the body against colonisation by disease-causing organisms adhesive forces forces acting between molecules of a substance and molecules of another substance alkali substance which produces an alkaline solution (containing hydroxide ions) with a ph greater than 7 amino acid basic unit of protein; a protein is made up of hundreds or even thousands of amino acid units apocrine gland releases sweat which helps with cooling by evaporation; found alongside coarse hair bacilli rod shaped bacteria bacteria single celled procaryotic organisms belonging to the protist kingdom beading becoming sphere-shaped biodegradable a substance capable of being broken down by the action of living organisms capsule cylinder shape with rounded ends, usually made of gelatin and in two parts that can be opened cocci sphere-shaped bacteria; coccus is one bacterium cohesive forces forces acting between molecules of the same substance eg. hydrogen bonds between water molecules colloid mixtures where large molecules or small clusters of molecules are dispersed through the liquid and do not settle out vi Lifestyle Chemistry

13 dermal patch dermis disperse dissolution dissolving emulsifier emulsifying agent emulsion enteric coated enzyme epidermis ethanol fibroblast gall bladder hair hair bulb hair follicle helical hydrophobic hydrophilic hydroxide group immiscible keratin thin medicated strip applied to the skin; delivers medication to the body through the dermis eg. nicotine patch innermost layer of skin containing sweat glands, heat sensors, thermoregulators and blood vessels to spread out dissolving a solute mixing with a solvent, forming a solution emulsifying agent eg. soaps, gums, sulfonates, quaternary ammonia compounds material which makes it possible to stabilise a colloid or emulsion dispersion of a liquid in another liquid in which it is immiscible coated with a stomach acid resistant layer that dissolves in the alkaline small intestine protein which is a catalyst for a biochemical reaction such as protein synthesis or hydrolysis of fat outermost layer of skin; protects the underlying tissue, forms a barrier from heat loss, water loss and micro-organisms CH 3 CH 2 OH colourless liquid alcohol, miscible with water; produced by yeast fermentation of a sugar cell which maintains skin elasticity stores bile to aid the digestion of fats traps heat on the surface of the skin; insulation layer site of hair growth the under skin section of hair spiral shaped water repelling attracted to water hydrogen atom and oxygen atom joined together often as a negatively charged ion OH - incapable of mixing to form a solution tough protein present in the epidermis of vertebrate organisms; in hair, feathers, fingernails Introduction vii

14 large intestine part of the alimentary canal (digestive system); absorbs water from wastes to produce faeces liver lymph melanin melanocyte meniscus methanol microbes micro-organisms mite mixture mould muscle narcosis narcotic non-polar oesophagus pancreas pathogen produces and sends bile to the gall bladder to aid the digestion of fat liquid, mostly water from blood, drained from the spaces between cells back to the circulatory system near the heart pigment present in skin and hair; its presence or absence determines colouring of skin and hair produces and injects melanin into surrounding cells for skin pigmentation the surface shape of a liquid; dependant on cohesive forces between molecules and the adhesive forces between molecules and the container. CH 3 OH colourless liquid alcohol; miscible with water; microscopic single celled organisms microscopic single celled organisms very small arthropod; some are free living; some are parasitic two or more substances not chemically combined fungal growth tissue involved in movement; causes hair to become erect, trapping warm air close to the surface of the skin, helping temperature regulation general anesthesia drug producing narcosis molecule with no electric charge; non-ionic tube connecting the mouth to the stomach produces enzymes which aid digestion of proteins, lipids and carbohydrates disease-causing organisms ph hydrogen ion concentration; ph = - log [H + ]; ph scale commonly ranges from 0 to 14; measure of acidity and alkalinity polar a molecule containing an electric charge; ionic viii Lifestyle Chemistry

15 polymer rectum sebaceous gland sebum secondary hair slow-release small intestine soluble solution solvent staphylococci stomach subcutaneous layer subdermal implant surfactant suspension sweat gland synthetic vellus hair yeast a large molecule made of a chain of monomers with the same chemical structure stores and passes intestinal waste to the exterior through the anus produces oils to lubricate the hair and skin oil produced by sebaceous glands in the dermis darker, wiry hairs emerging after puberty from vellus hair follicles designed to provide slow release over time site of digestion and absorption of the products of digestion capable of dissolving contains dissolved substances that are uniform throughout, is transparent and may be coloured; the solute is dissolved entirely in the solvent the substance in which a solute dissolves cocci bacteria appearing in grape-like formations site of protein digestion; contains strong acid in gastric juices consists of larger connecting veins and arteries and fatty tissue to help insulate the body inserted under the skin to release medication over a period of time surface active agent with one end of each molecule capable of dissolving in water and the other capable of dissolving in oil; substance that lowers the surface tension of a liquid insoluble solids suspended in liquids; the solids eventually settle upon standing excretes saline water; releases body heat through evaporation of sweat (cooling) artificial as opposed to natural; made in a laboratory or chemical factory fine, short, fair hair covering the body single celled fungus; used in brewing and baking Introduction ix

16 Gill Sans Bold Senior Science HSC course Stage 6 Lifestyle chemistry Part 1: The substances you use IncorporatingOctober2002 AMENDMENTS

17 Senior Science Stage 6 HSC Course Lifestyle Chemistry The substances you use Mixing it up Your skin What s growing on your skin? Dissolve it! Good medicine Medical Technology Bionics Information Systems Option

18 Gill Sans Bold Contents Introduction... 2 Common substances... 4 Substance use in retail...5 Properties of substances...6 Mixtures... 8 Solutions, suspensions and colloids...9 Colloid types Colloid classification...19 Making colloids and suspensions...21 Summary Appendix Appendix Suggested answers Exercises Part Part 1: The substances you use 1

19 Introduction At the end of Part 1 you should be able to: classify some common substances as solutions, suspensions or colloids; make some suspensions, solutions and colloids and appreciate the wide range of chemicals we regularly use from food to paint. Be aware that Part 1 should take around six hours to complete. In Part 1, you will be given opportunities to learn to: identify that a wide range of substances are used daily as part of our food, our hygiene, our entertainment and maintenance of our health identify that solutions, colloids and suspensions occur in a wide range of consumer products explain that mixtures can be solutions that contain dissolved substances and are uniform throughout suspensions containing particles that settle out, or form layers, quickly colloids with particles that remain suspended for long periods of time and include liquid-in-liquid (emulsions) oil-in-water water-in-oil gas-in-liquid (foams) In Part 1, you will be given opportunities to: process and analyse information to identify the range of chemicals used in every day living including: detergent lubricant pesticide solvent 2 Lifestyle chemistry

20 Gill Sans Bold metal cleaner body hygiene chemicals cosmetic and outline any precautions that may be needed in the use and handling of these chemicals use first-hand or secondary sources to gather, process, analyse and present information to identify examples of suspensions and colloids and outline one advantage of a mixture being in each form plan, select appropriate equipment or resources for, and perform a first-hand investigation to produce a range of suspensions and colloids that are used by consumers including beaten or whisked eggs salad dressing (oil/ vinegar) mayonnaise Extract from Senior Science Stage 6 Syllabus Board of Studies NSW, October The most up-to-date version is to be found at Part 1: The substances you use 3

21 Common substances A substance is the material of which something consists. What substances do you use every day? Have you ever wondered what these substances are made of? Why would you use some things for some substances and not others? Would you use soap as hair conditioner? Would you use dishwashing liquid to moisturise your skin? Would you use window cleaner to wash the family car? Why not? Why are substances used for specific purposes? 1 List all the substances you use, every day from the time you wake up in the morning until you go to bed at night. This includes the types of food you eat, hygiene, entertainment, cleaning and health needs. Don t be surprised if you don t have enough room for your answer! Were you surprised with the amount of substances you use each day? Think about other people and the substances they use each day. They may use: cosmetics; dental floss; hairspray; shaving cream; perfume or after shave; vitamins; skin creams; laundry detergents; and cleaning products. 2 Can you think of any other substances other people use daily? Businesses can use quite different substances on a daily basis than you use. These substances are discussed in the following section. 4 Lifestyle chemistry

22 Gill Sans Bold Substance use in retail The following businesses use many different substances. Some of these are listed below. 1 For each of the following businesses, add two more substances you assume the business uses regularly. If you are unsure, ask someone for help. a) Hair salon hair dyes hair mousse perming solution b) Cafe cooking oil disinfectant (for mopping floors) detergents (for washing dishes) c) Service station engine oil water unleaded petrol Check your answers. 2 Can you think of another retail industry and the substances it uses? Record your answer below. Turn to Exercise 1.1 at the back of this part to identify a range of common chemicals used in everyday living. Part 1: The substances you use 5

23 Properties of substances A property is a characteristic or feature of something. Can you suggest a property of a chemical? Some properties of a chemical are: state of matter (solid, liquid, gas); colour; density; melting point; reaction with oxygen; reaction with acid and so on. The properties of a chemical depend on: the particles that make up the chemical how the particles are arranged the forces (interactions) between the particles. There are two main types of properties of chemicals physical properties and chemical properties. A knowledge of these properties is important in identifying the characteristics of a particular chemical. Physical properties A physical property is a property of the substance by itself. For example: state of matter colour density how it feels to touch odour taste. Sometimes you rely on the physical properties of a substance for its use. You wouldn t wear perfume or after shave unless it had the physical property of odour. You eat certain foods for their taste. You choose particular paint for its physical colour properties. Write down the physical properties of two other substances you use. 6 Lifestyle chemistry

24 Gill Sans Bold Chemical properties A chemical property is a property of the substance reacting with another chemical. Chemical properties are what we observe when a substance reacts with another chemical. You have probably heard of elements, compounds and mixtures. Briefly, elements are made up of only one type of atom. Pure gold is an example of an element, containing only gold atoms. Compounds contain more then one type of atom joined together. Water (H 2 O) is an example of a compound as it contains two hydrogen atoms and one oxygen atom joined together. Mixtures contain different substances not chemically combined. Mixtures can often be separated by a process based on the physical properties of the compounds. This module focuses on mixtures. You use mixtures each time you wash your face, brush your teeth, drink soft drink, bake a cake, moisturise your skin and the list goes on. Sometimes you rely on the chemical properties of a substance to achieve a desired outcome. Examples are: cake mixture changes from a liquid to a solid when baked some paint strippers react chemically with paint to remove it hair dye reacts chemically with hair and oxygen to colour the hair. Chemical reactions are often very difficult to reverse. For example a cake cannot be unbaked and the milk and flour separated. Sometimes we rely on both the physical and chemical properties of a substance. The hair dye example has important chemical properties, however the resultant physical property of colour is also important. Can you think another example of a substance you use due to its chemical properties? Part 1: The substances you use 7

25 Mixtures Mixtures consist of more than one substance. Air is a mixture of gases such as oxygen, nitrogen, carbon dioxide and hydrogen. The substances you use will fall into three categories. 1 Use the code table below to determine the three types of mixtures. a) solutions b) suspensions c) colloids a b c d e f g h i j k l m n o p q r s t u v w a b c d e f g h i j k l m n o p q r s t u v w 2 Do you know what the above terms mean? Refer to the Glossary at the beginning of this module to define each of the three types of mixtures, from question 1. a) b) c) Check your answers. 8 Lifestyle chemistry

26 Gill Sans Bold Solutions, suspensions and colloids You might be wondering what solutions, suspensions and colloids are. Their definitions are listed below. Solution Solutions contain dissolved substances that are uniformly spread throughout the solvent. A true solution is transparent and may be coloured. The solute is dissolved entirely in the solvent. Suspension Insoluble solids suspended in liquids are called suspensions. The solids eventually settle upon standing. Colloid Mixtures where large molecules or small clusters of molecules are dispersed through the liquid and do not settle out are colloids. The particles in a colloid have the same electric charge on their surface. This common electric charge repels the particles from one another and keeps them dispersed and moving throughout the liquid. The particles cannot join together to form a particle large enough to settle out. Fine negatively charged clay particles and charged protein on the surface of butter fat droplets in milk make fine clay in water and milk colloids. The protein and nucleic acid molecules floating in the fluid of living cells are colloids. The table on the following page outlines the characteristics of each type of mixture at a glance. You will notice that the particle size; settling of particles to the bottom of the mixture; residue left after filtering; a light beam visible in the mixture when shone though the mixture; and the effect of an electric current or an electric field are all measurable characteristics that define a mixture as a solution, suspension or colloid. Part 1: The substances you use 9

27 Characteristics Solution Suspension Colloid particles smaller than 10-6 mm particles larger than 10-3 mm particles between 10-3 and 10-6 mm settling of particles residue left after filtering a light beam can be seen in the mixture affected by an electric current or field You should now be aware of the characteristics that define solutions, suspensions and colloids From the table above, record all the characteristics of each mixture type. Some have been done for you as a guide. a) Characteristics that define a solution are: particles smaller than 10-6 mm ( mm) no settling of particles b) Characteristics that define a suspension are: particles larger than 10-3 mm (0.001 mm) and can be seen under a light microscope 10 Lifestyle chemistry

28 Gill Sans Bold c) Characteristics that define a colloid are: particles are between 10-3 mm and 10-6 mm (0.001 mm and mm) Check your answers. You can use the characteristics that define solutions, suspensions and colloids to determine which of the three categories some common household substances belong to. Predict the categories each of the following mixtures, based on your current knowledge. (The object of this exercise is to start you thinking about the properties of different substance. This does not mean you have to be right.) Mixture Solution/suspension/colloid a) sugar in water mixture b) salt in water mixture c) milk in water mixture d) coffee in hot water mixture e) flour in water mixture f) soil in water mixture Are you ready to investigate which category those substances actually belong to? The activity on the following page investigates the characteristics of each substances above, helping you to identify each mixture as a solution, suspension or colloid. Part 1: The substances you use 11

29 Substance classification Aim To investigate the properties of mixtures and use these properties to classify the mixtures as solutions, suspensions or colloids. Apparatus You will need to collect: teaspoon filter paper or paper towel or sugar coffee filters from supermarket salt two glasses or transparent cups milk funnel coffee pen-sized laser pointer (these are class 1 or 2 lasers with a flour power output of < 1 milliwatt) soil OR a torch with scissors, cardboard and rubber band Method (best at night in a room which can be darkened) You can use the pen sized laser pointer as your light source but DON T LOOK DIRECTLY AT THE LASER LIGHT BEAM. If a laser pointer is not available prepare a torch as shown in steps 1 to 5. torch face 1 Place your torch face down on a piece of cardboard and trace around the torch face. 2 Draw a second circle outside the first circle from step 1. cardboard 3 Cut around the larger circle. Place a hole in the centre using a pen. 4 Cut inwards towards the centre circle to create tabs. hole 12 Lifestyle chemistry

30 Gill Sans Bold cardboard hole beam of light rubber band torch 5 Fold the tabs and place the cardboard over the torch face, securing it with a rubber band as shown. When the torch is on, a beam of light should come through the hole in the cardboard. Record your observations in the table on page 12 as you work through the method: 6 Place a teaspoon of sugar in half a glass of water and stir twenty times. This prepares a mixture of about 1% concentration. 7 Shine the beam of light through the sugar solution. Looking from the side can you see the light beam in the solution? 8 If you have round filter paper, fold it in half as shown in the diagram. If you are using paper towel, cut it into a circle shape with minimum diameter of 15 cm, then fold it in half. A coffee filter can be placed over the top of a glass or cup. 9 Fold the filter paper (or paper towel) in half again, then open out the paper to form a cone shape as shown. A coffee filter is already made in a cone shape. 10 Place the filter paper inside the funnel with a glass or cup underneath to catch the filtered solution. You may need to moisten the funnel with water to keep the filter paper inside the funnel. You will need a new piece of filter paper or paper towel to filter each of the mixtures. 11 Filter the first substance by gently pouring the sugar mixture into the filter paper, not allowing it to fill above the filter paper. 12 Leave the mixture to filter. Do any particles settle out? Is any residue left on the filter paper? 13 Make and test mixtures: salt with water; milk and water; coffee and water; flour and water; and soil and water using the mixing directions from Step 6. Part 1: The substances you use 13

31 14 Repeat steps 7-12 with salt mixture, milk mixture, coffee mixture, flour mixture and soil mixture. 15 Identify each type of mixture as a solution, suspension or colloid. Results Record your observations below. Solute Light beam Filtering Settling particles Solution or suspension or colloid? sugar salt milk coffee flour soil 1 Look at the characteristics that define a solution, suspension and colloid (on the previous pages). State which category each mixture belongs in. Explain your answer based on your results. _ 2 Can you give other examples of common solutions, suspensions and colloids? (Remember they must have all the characteristics of a solution, suspension or colloid) a) solutions b) suspensions 14 Lifestyle chemistry

32 Gill Sans Bold c) colloids Check your answers. How do you think you could tell the difference between a solution, suspension and a colloid? Solutions appear clear, leave no residue when filtered and a light beam cannot be seen in the solution. Suspensions contain insoluble solids that will eventually settle, forming layers upon standing. Residue is left when filtered and a beam of light can be seen in the suspension. Colloids are mixtures of large molecules or small clusters of molecules dispersed in a liquid. Colloids are not clear, a beam of light can be seen in the colloid, and no residue is left after filtering. If the particles in these mixtures were magnified about one million times they could look like this: solution particles suspension particles colloid particles edge of a round suspension particle The particles in a solution are much smaller than the wavelength of light. The particles in a suspension and colloid are larger than or similar in size to the wavelength of light and can scatter the light showing the beam. You are about to classify some common substances as solutions, suspensions and colloids. Use this information to help you classify. Turn to Exercise 1.2 at the back of this part to classify some common substances as solutions, suspensions or colloids. Part 1: The substances you use 15

33 Colloid types You already know that colloids are mixtures where the particles between 10 6 and 10 3 mm are dispersed in a liquid and don t settle out. There are several types of colloids. The main colloid types you need to study are: solid-in-liquid such as water-based paint, ink, jelly, toothpaste gas-in-liquid foams such as mousse, whipped cream liquid-in-liquid emulsions such as oil-in-water or water-in-oil. You may be surprised to find that some substances you commonly use fit into one of these colloidal categories. Often two different substances don t mix well and require an emulsifying agent or emulsifier. The added emulsifying agent produces a stable dispersion of one liquid in another eg. soap added to oil and water. An emulsifier is a surfactant. It coats droplets of liquids eg. oil, causing them not to stick to other oil molecules, therefore allowing them to be dispersed through a liquid it is not soluble in directly. emulsifier oil water oil Emulsifier stabilising droplets of oil in water An emulsion is therefore a uniform mixture of two substances that are normally immiscible. The term immiscible means unable to dissolve in another substance eg. oil is immiscible in water. Protein is often used as an emulsifying agent with food oils. In mayonnaise the protein in egg coats food oil droplets, allowing the oil to be dispersed through water. 16 Lifestyle chemistry

34 Gill Sans Bold Detergents are emulsifying agents. They are attracted to the surfaces between oil and water. As soon as oil is broken up into droplets the emulsifying agent coats the droplets stopping them from joining together. This disperses the oil in water rather than leaving oil attached to plates and cups. The oil droplets do not join because of the emulsifier coating. Think about oil and water. Oil usually floats on the surface of water. An oil-in-water colloid has small oil droplets dispersed through water. An emulsifying agent ensures the droplets are dispersed throughout the water, at least for a short period of time depending on the properties of the emulsifying agent. Gas-in-liquid Can you think of any substances that are foamy? Many of them are used in the bathroom. These are all gas-in-liquid colloids. Examples of gas-in-liquid colloids are: soap suds hair mousse shaving foam beer foam soft drink foam whipped cream. The foam that forms on the top of beer and soft drink consists of bubbles of carbon dioxide gas in liquid. As the bubbles burst the gas part is lost to the air and the liquid part joins the rest of the liquid. Liquid-in-liquid A mixture of two liquids where one is dispersed in the other is a liquidin-liquid colloid or emulsion. Examples of emulsions are: milk mayonnaise coffee and tea with milk cream. Part 1: The substances you use 17

35 Two very common types of liquid-in liquid colloids are: 1 Oil-in water colloids such as: water based salad dressings some water-based moisturisers sunscreen milk and cream 2 Water-in-oil colloids such as: oil-based moisturisers oil-based salad dressings butter A way of distinguishing between oil-in-water and water-in-oil colloids In an oil-in-water emulsion such as milk the oil droplets are dispersed in water. If a drop of water soluble dye is added to an oil-in-water emulsion the dye colour spreads and the emulsion appears the dye colour. water soluble dye water oil In a water-in-oil emulsion such as butter the water droplets are dispersed in oil (butter fat in the case of butter). Here the water soluble dye will not be able to spread its colour throughout the emulsion. water soluble dye oil water. 18 Lifestyle chemistry

36 Gill Sans Bold Other ways of distinguishing between the two main types of liquid-inliquid use the temperature feel of skin and electrical conductivity. Oil-in-water colloids like cold cream feel cold to the skin. Water has a high capacity for absorbing heat. Heat moves quickly from the skin into the water and so the oil-in-water cream feels cold. By contrast water-inoil colloids like ointments do not feel cold. The oil does not absorb much heat from the skin. Oil-in-water colloids are better electrical conductors than water-in-oil colloids Colloid classification Remember that all water-in-oil emulsions and all oil-in-water emulsions are also liquid-in-liquid emulsions. For example, milk is a liquid-inliquid emulsion and an oil-in-water emulsion. Butter is a water-in-oil emulsion and a liquid-in-liquid emulsion 1 Classify the following liquid-in-liquid emulsions as oil-in-water emulsions or water-in-oil emulsions. To do this, you will have to determine if the substance consists primarily of oil or water. If the emulsion is primarily oil it would be a water-in-oil emulsion. a) milk b) mayonnaise c) coffee or tea with milk 2 Use the information on the previous pages to match the products in the Appendix 1 with the types of colloids below. Cut out the products in the Appendix 1 and stick them in the appropriate colloid column below. Part 1: The substances you use 19

37 Liquid-in-liquid colloid Gas-in-liquid colloid Oil-in-water Water-in-oil Check your answers. You will now create your own colloids and suspensions. This is not as difficult as it sounds. You don t need complicated scientific equipment or chemicals. Almost every time you cook something in your kitchen where at least one ingredient is a liquid eg. milk, oil, melted butter, water, cream, juice, honey or vinegar, you make a colloid or suspension. 20 Lifestyle chemistry

38 Gill Sans Bold Making colloids and suspensions Are you ready to turn your kitchen into a laboratory? Are you a good cook? You should enjoy eating your results! Your aim is to produce a range of colloids and suspensions. Look up recipes for: meringues salad dressing with oil and vinegar mayonnaise smoothies. Recipes for the foods listed are available in Appendix 2. If you are not satisfied with these recipes, you may choose to use other recipes from cook books at home or ask your family and friends for recipes. Each of these recipes will demonstrate one form of colloid or suspension. You must: find and record recipes record the equipment and ingredients you will need make the mixtures from the recipes identify the type of colloid or suspension for each mixture. One of the above recipes will settle out suspended solids if left standing for a period of time, indicating it is a suspension. State which mixture is a suspension in your conclusion. Turn to Exercise 1.3 to plan, carry out and report on your experiment. Advantages Why do you put sugar in your tea instead of consuming it separate to the tea? Why do you mix ingredients together, making a cake rather than eating them separately? You answers are probably because they taste better. There are advantages to sugar dissolving in tea, forming a solution; and making a suspension such as a cake mixture. What advantages do solutions, suspensions and colloids have? Part 1: The substances you use 21

39 List three advantages for each of the following solutions, suspensions and colloids. It may help you to think about the different products that can be made in each case eg. suspending sand and gravel in liquid cement helps the cement become firm when dry. 1 Dissolving sugar in water to form a solution. _ 2 Suspending solid particles in a liquid to form a suspension. _ 3 Mixtures of substances being even throughout by forming a colloid. _ Check your answers. Medicines in suspension form Some medicines contain fine, undissolved particles suspended in a liquid base e.g. calamine lotion. The particles settle to the bottom of the containers after prolonged standing. It is important to shake a suspension well before use to evenly distribute the drug particles. Any medicine labeled suspension, lotion or emulsion should be checked for an instruction to shake well before use. 22 Lifestyle chemistry

40 Gill Sans Bold Summary 1 Match the following substances with the category it belongs to by drawing a line from the right column to the left column. You may use Exercise 1.1 as a guide. detergent lubricant pesticide solvent metal cleaner body hygiene chemicals cosmetics moisturiser Brasso dishwashing liquid engine oil turps fungicide shampoo 2 You are now aware that substances you use regularly are solutions, colloids or suspensions. Refresh your memory by writing: solutions; colloids; or suspensions above each of the following definitions. a) Mixtures where particles between 10 6 and 10 3 mm are dispersed through the liquid and do not settle out. b) Insoluble solids suspended in liquids. The solids settle upon standing. Such substances require shaking before use. c) Mixtures containing dissolved substances that are uniformly spaced throughout and appear clear. The solute is dissolved entirely in the solvent. Part 1: The substances you use 23

41 3 a) What are three different types of mixtures? b) What are the main types of colloids? c) Name two common liquid-in-liquid colloids. Check your answers. 24 Lifestyle chemistry

42 Gill Sans Bold Appendix 1 Part 1: The substances you use 25

43 26 Lifestyle chemistry

44 Gill Sans Bold Appendix 2 Meringue Ingredients 1 1 / 2 cups of castor sugar 1 teaspoon cornflour 2 egg whites 1 / 2 a teaspoon of vanilla 1 teaspoon vinegar 4 tablespoons of water Method 1 Preheat the oven at the lowest possible temperature ( C). 2 Place all ingredients in a bowl and beat with an electric mixer until shiny. This is as far as you need to go to do Exercise 1.3. To make the cooked meringue continue with steps 3 and 4. 3 Desertspoonfuls of mixture may be placed onto a greased or lined tray or the mixture may be placed in a piping bag and piped onto a greased or lined baking tray. 4 Bake in a slow oven for one and a half hours or until dry and crisp. Salad dressing Ingredients 1 / 2 a cup of vinegar 3 / 4 of a cup of vegetable oil 1 / 2 a teaspoon of vanilla 1 / 2 a teaspoon of mustard 1 / 2 a teaspoon of salt pinch of black pepper 1 / 2 a teaspoon of sugar 1 clove of garlic or half a teaspoon of crushed garlic Part 1: The substances you use 27

45 Method Blend all ingredients with a blender, food processor or hand mixer or place all ingredients in a jar and shake. Mayonnaise Ingredients 1 1 / 2 teaspoons of mustard 1 cup of vinegar or lemon juice 400 g can of sweetened 1 teaspoon of salt condensed milk 1 egg Method Beat all together with a whisk, electric beaters or hand blender until well mixed. It will thicken in the refrigerator. 28 Lifestyle chemistry

46 Gill Sans Bold Suggested answers Substance use in retail 1 a) Hair salon: hair spray; hair gel, shampoo and conditioner are some other substances. b) Cafe: milk for coffee and tea; and breads, fruit and vegetables are some other substances. c) Service station: diesel fuel; and natural gas are some others. Mixtures 1 a) solutions b) suspensions c) colloids 2 a) Solutions contain dissolved substances that are uniformly spread throughout, are transparent and may be coloured. b) Mixtures where insoluble solids are suspended in liquids are suspensions. The solids eventually settle to the bottom upon standing. c) Colloids are mixtures of solute and solvent where large molecules or small clusters of molecules are dispersed through the liquid and do not settle out. Solutions, suspensions and colloids a) Characteristics that define a solution are: particles smaller than 10-6 mm ( mm) no settling of particles an electric field has no effect on the solution no residue is left after passing through filter paper a light beam shone through a solution cannot be seen in the solution. Part 1: The substances you use 29

47 b) Characteristics that define a suspension are: particles larger than 10-3 mm (0.001 mm) particles settle out on standing an electric field has no effect on the mixture residue is left after passing through filter paper a light beam can be seen when shone through the mixture. c) Characteristics that define a colloid are: particles are between 10-3 mm and 10-6 mm (0.001 mm and mm) particles do not settle out on standing an electric field will cause some particles to move to one electrode no residue is left after passing through filter paper the path of a light beam can be seen when shone through the mixture. Substance classification 1 Sugar and salt in water are solutions because they are both clear, transparent and leave no residue when filtered. Soil and flour in water are both suspensions as a layer of solids settles out over a period of time. Milk in water and coffee in water are typically colloids as neither will settle out solids over time and no residue is left after filtering (although this depends on the type of coffee you used; ground coffee will usually settle out a solid layer indicating it is a suspension). 2 a) Some common solutions are wine; spirits; and nail polish remover. b) Some common suspensions are tea leaves in water; ground coffee in water; liquid cake mix. c) Some common colloids are milk; mayonnaise; egg white in water; and cream. Classifying colloids 1 a) Milk is an oil-in-water colloid. b) Mayonnaise is a water-in-oil colloid (the oil-based variety). c) Coffee or tea with milk are both oil-in-water colloids. 30 Lifestyle chemistry

48 Gill Sans Bold 2 Liquid-in-liquid colloid Gas-in-liquid colloid Oil-in-water Water-in-oil Advantages 1 Dissolving sugar in water can make a drink sweeter, or into a toffee or a syrup. 2 Advantages of suspending solid particles in a liquid are: small solids can be used in cosmetics as exfoliants; solid particles in liquids can provide the basis for coatings such as nail polish; and toothpaste contains fine solid particles as abrasives to remove plaque from teeth. 3 Advantages of mixtures that are even throughout are: oils used for cooking, vitamins and proteins are available to skin in moisturisers; oil droplets in milk help it taste better; and hair gel contains substances which help hair styling. Part 1: The substances you use 31

49 Summary detergent lubricant pesticide solvent metal cleaner body hygiene chemicals cosmetics dishwashing liquid engine oil fungicide turps Brasso shampoo moisturiser 2 a) Mixtures where particles between 10 6 and 10 3 mm are dispersed through the liquid and do not settle out. b) Suspensions are insoluble solids suspended in liquids. The solids settle upon standing. Such substances require shaking before use. c) Solutions are mixtures containing dissolved substances that are uniformly spread throughout and appear clear. The solute is dissolved entirely in the solvent. 3 a) Three types of mixtures are solutions, suspensions and colloids b) The main types of colloids are gas-in-liquid; liquid-in-liquid; solid-in-liquid. c) Two colloid types that are liquid-in-liquid colloids are: oil-inwater and water-in-oil emulsions. 32 Lifestyle chemistry

50 Gill Sans Bold Exercises - Part 1 Exercises 1.1 to 1.3 Name: Exercise 1.1 Are you ready to investigate the chemicals behind the substances you commonly use? Look for examples of the following substances in your home. If you cannot find all of these substances at home, are you able to visit a cousin, friend or neighbour? Perhaps a visit to your local supermarket might be quicker. In this task you must observe the labels for ingredients and safety precautions for each of the eight substances listed in the table on the following page. You need to record: the trade name eg. Sunlight dishwashing liquid the number of different chemicals listed in the substance. (Count the ingredients from the label) record the main ingredient (the first one on the ingredients list) or the active ingredient(s) precautions required for handling the substance. Some items may have only an active ingredient on the label, others may have no ingredients listed. Do your best to fill the entire table on the following page, then answer the questions that follow. Part 1: The substances you use 33

51 Substance Examples Trade name Number of chemicals listed Main ingredient Active ingredient Precautions for use detergent dishwashing or laundry detergent (without enzymes) lubricant Vaseline or engine oil fungicides solvent pesticide nail polish remover or turps Brasso or silver cleaner body hygiene chemicals metal cleaner shampoo, soap or deodorants cosmetics moisturiser, foundation, or lipstick 34 Lifestyle chemistry

52 Gill Sans Bold 1 What substances appear to contain the greatest number of ingredients? 2 Which substances have detailed precautions for use? 3 Choose two substances with safety precautions listed on the label. What effect could these substances have if the precautions were not followed? Exercise 1.2 Are you ready to classify some common substances as solutions, suspensions or colloids? You may refer to the information on pages 9 to 15 to help you determine which classification each substance belongs in. You are to: find, observe and classify six of the following substances: soft drink; shaving foam; nail polish remover; nail polish; turps, deodorant or antiperspirant; after shave or perfume; paint; moisturiser; and hair conditioner observe and classify two other items at home as solutions, suspensions and colloids. If you cannot find these substances at home, can you visit a supermarket, cousin, friend or neighbour? An example is provided on the following page as a guide. Part 1: The substances you use 35

53 Substance and trade name orange juice Today s Fresh Observations not clear can see a beam of light in substance particles have settled to the bottom, forming a layer Solution, suspension or colloid suspension 36 Lifestyle chemistry

54 Gill Sans Bold Exercise 1.3 Normally you do not taste chemicals or mixtures of chemicals. However when you use Appendix 2 you make colloids and suspensions that you can taste. Plan and carry out your tasty experiments on making colloids and suspensions. Aim State what are you trying to do. Apparatus Record the equipment and ingredients you will require while making the three recipes below. Appendix 2 contains recipes for each. If you use an alternative recipe indicate the different ingredients and equipment. Recipe Ingredients Equipment required salad dressing mayonnaise meringue Part 1: The substances you use 37

55 Method Record, or stick in copies of each recipe. If your recipes are larger than the spaces provided, you may copy them onto sheets of paper, fold them and stick them in the spaces below. Meringue Mayonnaise Salad dressing 38 Lifestyle chemistry

56 Gill Sans Bold Results Classify each mixture prepared as a: suspension or colloid: gas-in-liquid liquid-in-liquid solid-in-liquid Recipe Suspension or colloid classification meringue mix before cooking meringue mix after cooking mayonnaise salad dressing You may wish to take photos of your creations and attach them with this exercise. Conclusion Use the criteria of colloids and suspensions to explain why each recipe mixture is classified as you indicated above. Part 1: The substances you use 39

57 Gill Sans Bold Senior Science HSC course Stage 6 Lifestyle chemistry Part 2: Mixing it up IncorporatingOctober2002 AMENDMENTS

58 Senior Science Stage 6 HSC Course Lifestyle Chemistry The substances you use Mixing it up Your skin What s growing on your skin? Dissolve it! Good medicine Medical Technology Bionics Information Systems Option

59 Gill Sans Bold Contents Introduction... 2 Surface tension... 4 Walking on water...5 Water drops on leaves...6 Why are water drops spheres?...6 Optional activity...9 Water under gravity...11 Menisci...11 Surfactants Use or surfactants...14 Emulsions Emulsifiers...19 Emulsion types...21 Biodegradability Soaps and detergents...23 Summary Appendix Appendix Suggested answers Exercises Part Part 2: Mixing it up 1

60 Introduction If you have ever wondered why water beads on polished cars; how some insects walk on water; why detergents clean grease off plates; and what is really meant by biodegradable, you will find out in Part 2. Don t be surprised to find the reasons why substances you use, do what they do. In Part 2, you will be given opportunities to learn to: explain surface tension in terms of the forces experienced by particles at the surface of a liquid describe surfactants as substances that affect the surface tension of a liquid state the relationship between the properties of an emulsion and the types of molecules present outline the purpose of the emulsifying agent in a range of consumer cleaning products identify that soaps and detergents are emulsifying agents and surfactants explain why cleaning agents must be surfactants and emulsifiers define the term biodegradable discuss the biodegradability of soaps and soapless detergents In Part 2, you will be given opportunities to: perform first-hand investigations to demonstrate the effect of surface tension and: the shape of liquid drops the formation of menisci the ability of some insects to walk on water process and present diagrammatic information to describe the effects of soaps, skin cleansers and shampoos on the solubility of oil perform a first-hand investigation to prepare an emulsion and compare its properties to those of a solution and suspension 2 Part 2 Lifestyle chemistry

61 Gill Sans Bold plan, choose equipment or resources for, and perform a first-hand investigation to gather information about the properties of different emulsions and use available evidence to compare those properties Extract from Senior Science Stage 6 Syllabus Board of Studies NSW, October The most up-to-date version is to be found at Part 2: Mixing it up 3

62 Surface tension Water molecules are strongly attracted to each other. Water molecules on the surface of water are strongly attracted to the surrounding surface molecules and the molecules beneath the surface. This strong attraction causes the surface of the water to resist attempts to increase its surface area, thus allowing objects denser than water to sit on the surface. This is a physical property of water. Refer to the diagram below. the water molecules are strongly attracted to each other pin force due to gravity Surface tension resists the gravitational force of the pin. 1 Gently place a metal pin or a paper clip on the surface of a glass of water. Try not to break the water surface with your fingers. Keep trying until you float the pin or paper clip on the water surface. If your pin or paper clip sinks, try again with another dry pin. Don t use pins with a pearl end as these tend to break the water surface and sink. Use the above information to explain why a pin, which is clearly denser than water, is able to float on the surface of water. Check your answer. 4 Part 2 Lifestyle chemistry

63 Gill Sans Bold Walking on water Water spiders rely on surface tension for mobility. They literally walk on water. Do you live near a waterway, lake, dam or other still water body? If so, you are able to observe the ability of some insects to walk on water. Aim To observe the variety of organisms that can walk on water. Method Go to your nearest water body. Walk along the edge of the water body, observing the insects that walk on water. Walk slowly so as not to disturb the insects. Record the number of different species you observe walking on water over a fifteen minute period. Results Make a tally of the different species of insects walking on water. Record the total number of species observed walking on water. Conclusion Fill in the blanks below. For example, Six different species were observed walking on water in the Darling River water course. different species were observed walking on water in the water body/course. Part 2: Mixing it up 5

64 Water drops on leaves Go outside and try to collect three waxy leaves. Use whatever method you can to place a single drop of water on the waxy surface of each leaf but be careful the water may roll off. Draw what each drop looks like on the leaf surface on the following page. leaf 1 leaf 2 leaf 3 Cross sections of leaves 1 What was the general shape of the water on the leaves? 2 Can you explain why the water formed that shape? Check your answers. Why are water drops spheres? Each molecule of water is attracted to the surrounding molecules from above, below and either side. On the surface of water, water molecules are attracted only to the molecules on each side and underneath. Water molecules on the surface are constantly being pulled towards the centre. For this reason water drops tend to form a sphere, reducing its surface area as much as possible. A two dimensional analogy may help you understand the behaviour of water drops. Imagine a president with twenty security guards. The security guards surround the president to protect him. Each security guard tries to stay close to other security guards. This represents the forces of attraction between water molecules. The security guards don t want to expose the president to an assassin. For this reason they will try 6 Part 2 Lifestyle chemistry

65 Gill Sans Bold to reduce the surface area exposed to assassins as much as possible, making a circle around the president. Water drops reduce their surface area as much as possible, simply because the forces between the water molecules in the drop of water are so strong just like the forces between the security guards and the president. Modelling a water drop You are about to make a model showing the internal forces of a water drop. For this activity you will need: toothpicks jelly snakes jelly lollies such as jellybeans or jelly babies 1 Break seven toothpicks into three even pieces. Each piece should be about 2 cm long. 2 Cut four snakes into three pieces each. Each piece should be about 4-5 cm long. 3 Collect six jelly lollies. (For the rest of this experiment, jelly lollies will be referred to as jellybeans because jellybeans were used for the illustrations. If you chose jelly babies, wild raspberries or another type of jelly lolly, these replace jellybeans throughout the experiment.) 4 Stick three toothpick pieces into a jelly bean. Each toothpick piece should be half sunk into the jelly bean and half sticking out. Refer to the diagram below which represents steps 4, 5 and 6. 5 Stick a piece of snake end-on onto the toothpicks attached to each jelly lolly. Refer to the diagram below, which also includes step 6. 6 Stick three more toothpick pieces on each end of the snake pieces as shown. Half of each toothpick piece should be showing. A jellybean represents a water molecule (H 2 O). The snakes represent the cohesive forces between water molecules. These are the forces attracting water molecules to other water molecules. The toothpicks only serve to join the jellybeans and snakes and are to be ignored in the model. Part 2: Mixing it up 7

66 7 Continue steps 4,5 and 6 until your model resembles the diagram opposite. The jellybeans in a row on the previous page represent the water molecules at the surface of water. The snakes represent the forces between water molecules on the water surface. The snakes pointing down represent the cohesive forces between water molecules on the surface and those beneath the surface. 8 Join the two ends of the chain, forming a circle. Attach the five inside snakes to a jelly bean in the centre as shown in the diagram opposite. Forces act between surface molecules and water molecules below the surface. When there are fewer water molecules beneath the surface, the surface molecules stick to those fewer molecules, causing the water surface to become circular. Your model demonstrates this with only one water molecule in the centre. In reality, there are thousands of water molecules inside a water drop, each with the cohesive forces described. In three dimensions, these cohesive forces cause a small amount of water to become spherical in shape. 8 Part 2 Lifestyle chemistry

67 Gill Sans Bold Explain how your model demonstrates why a water drop is spherical. Check your answer. Water drops are three dimensional. Do you want make your model three dimensional? If so, take the challenge by doing the following optional activity but don t dismantle your model you will need it for the following activity. If not, enjoy your model, but save some snakes, toothpicks and jellybeans for an experiment later in this part. Optional activity 1 Stick five toothpick pieces into the centre jelly bean and two toothpick pieces into the outside jellybeans each, as shown in the diagram opposite. 2 Attach a piece of snake to each of the toothpick pieces from above. 3 Attach another toothpick piece to the end of each snake as shown. 4 Join all the snakes with jellybeans as shown in the diagram opposite. (This may be fiddly but you can do it!) Part 2: Mixing it up 9

68 5 Stick a single toothpick piece into the five jellybeans from the previous step. See the diagram opposite. 6 Attach a piece of snake to each of the toothpick pieces from step five. Then attach all five pieces of snake to a single jelly bean on top. Your model should look like the one opposite. 7 Lastly, attach the top jelly bean with the one in the center at the bottom. This is shown in the diagram opposite. Congratulations! You just made a three dimensional model showing the cohesive forces between water molecules. Your model should resemble half a sphere. If you carried out the same steps on the other side of the model, it would become a complete sphere. This would resemble a water drop. List any problems you had while constructing the three dimensional model. Don t forget to save some snakes, jellybeans and toothpicks for later in this part. 10 Part 2 Lifestyle chemistry

69 Gill Sans Bold Water under gravity You may be wondering why a water drop from a tap is shaped like a tear drop instead of a sphere. The answer is gravity. The force of gravity causes the majority of water molecules to accumulate towards the bottom of the drop, leaving fewer molecules at the top. This causes the tear shape. 1 The diagram below shows a spherical water drop. Sketch over the top of the drop to show the effect of gravity on the drop of water. Spherical water drop. 2 Explain in your own words why falling water drops appear tear shaped. Check your answers. Other liquids such as oils, liquid mercury, alcohol and many more have different forces acting between molecules. These forces determine their surface shape. Menisci Have you ever noticed that the surface of water in a glass? The water surface curves up at the edges. This curved surface is the meniscus (plural: menisci). The water molecules are attracted to the glass through adhesive forces. Cohesive forces between water molecules cause them to stick together. Part 2: Mixing it up 11

70 The water prefers to stick to the glass surface, however these water molecules still attract other water molecules. The water molecules try to adhere to more of the glass surface, thus moving up the side of the glass. Other water molecules are attracted to these molecules and move with them. Gravitational forces will only allow the water to move a short distance. The result is the meniscus you see in a glass of water. The diagram below shows a meniscus of water. meniscus beaker water Meniscus of water. Turn to Exercise 2.1 at the back of this part to observe menisci. You may be wondering what all this has to do with Lifestyle chemistry. The forces acting on the surface of a liquid determine how it can be acted upon by surfactants. 12 Part 2 Lifestyle chemistry

71 Gill Sans Bold Surfactants Surfactants are molecules that act at the surface of a liquid, lowering the liquid's surface tension. Surfactants are shaped like tadpoles. The head is water soluble and the tail is oil soluble. There are four different types of surfactants: anionic (negatively charged head) cationic (positively charged head) non-ionic (no charge) amphoteric (positive and negative charges depending on the ph of the liquid). Use the above information to identify each type of surfactant below. Surfactant types. Part 2: Mixing it up 13

72 Use of surfactants Agricultural sprays When you observed a drop of water on a waxy leaf, you should have noticed the water beading or becoming a ball. If water is used as a solvent for agricultural sprays, the water is likely to bead and roll off the leaves with little effect on the plant. Surfactants are added to the water to minimise its surface tension. The surfactant molecules get between the water molecules at the surface. This reduces the attraction between the water molecules so that instead of having a strong outside layer able to form balls, the water spreads out. The water spreading over the surface of a waxy leaf coats it with the farm chemical. Refer to the diagram below. leaf Surfactants allowing chemical spray to spread over the surface of a waxy leaf. Fire fighting Silv-ex foam is used to fight fires. The foam reduces the surface tension of the water it s mixed with. The foam sticks to the surface of trees, grasses and other fire fuels, penetrating their surfaces and keeping them wet, thus reducing the risk of ignition. It also prevents oxygen from reaching the fuel. Cleaning Detergents, soaps, cleansers shampoo and many other cleaning products are surfactants. Their action is described in the following section. 14 Part 2 Lifestyle chemistry

73 Gill Sans Bold Froth floatation Froth floatation is used in mining. The crushed rock is mixed with water and aerated from below. The air bubbles rise through the mixture. The mineral particles are positively charged and readily stick to water molecules. When surfactants are added, the mineral particles stick to the negative surfactants. The surfactant s tails are more attracted to the air bubbles (rising through the solution) than to water, thus attaching to air bubbles and carrying the mineral particles to the surface. This separates the mineral from its ore. See the diagram below. froth air buble rising through the liquid negative polar head enlarged view metal ions air pumped through pipes under pressure Froth floatation of metal ions using air bubbles. Part 2: Mixing it up 15

74 Imagine you are a teacher. Your students must learn about the use of surfactants. Your students have the information on pages 13 and 14. Write three questions about the use of surfactants. The questions must be designed in a way that helps the students understand what surfactants do and why they are used. 1 2 _ 3 _ Many surfactants are also used in the home as emulsifiers. The next section introduces you to the emulsifiers you use every day. 16 Part 2 Lifestyle chemistry

75 Gill Sans Bold Emulsions You have already learnt about liquid-in-liquid colloids. All liquid-inliquid colloids are also emulsions. You may be wondering what the exact definition of an emulsion is. An emulsion is a mixture of tiny droplets of one liquid dispersed in another in which it is immiscible. Oil and water normally don t mix, but oil may be emulsified to allow it to mix with the water. Emulsification is the process of dispersing a liquid in another liquid in which it is immiscible as a stable colloidal dispersion. Certain substances are used as emulsifiers to hold one substance in another such as oil in water. Most, but not all, surfactants are emulsifiers. An emulsifying agent is a substance added to a mixture to stabilise an emulsion. The detergents you just learned about as surfactants are also emulsifiers. However, not all surfactants are good emulsifiers. You have dealt with surfactants with very polar heads. This means the heads have a charge on them. Non-ionic surfactants do not have very polar heads. These slightly polar surfactants do not emulsify well. Part 2: Mixing it up 17

76 Oils do not dissolve in water well (they are immiscible). Emulsifiers stabilise oil broken up into smaller globules when the oil is shaken with water. The emulsifiers then hold the oil globules in water, preventing them from forming larger globules or floating to the surface. After reading the boxed text on the previous page, you should understand that emulsifiers disperse an immiscible substance and hold it in colloidal form that is, dispersed in a liquid. If this seems too technical for you, the following paragraph using water and oil as an example may help. Understanding emulsification If you are finding it difficult to understand the action of emulsification, the following analogy may help. Imagine a gang of criminals in a group as a large oil globule. Police are the emulsifiers. They have the energy to hold one criminal each. A large number of police surround the gang, separating them into smaller groups. The police (surfactants) surround the smaller gangs, holding one criminal each. The smaller gangs (oil globules) are unable to join back together due to the force of the police (emulsifiers). 1 Can you think of another way to describe the action of emulsifiers? You should already know that cleaning agents contain surfactants. Liquids containing surfactants are more able to wet and cover the surface of immiscible liquids. Cleaning agents also need to be emulsifiers in order to allow immiscible substances to be dispersed in colloid form. 2 Why must cleaning agents contain surfactants and emulsifiers? _ 18 Part 2 Lifestyle chemistry

77 Gill Sans Bold 3 In a single paragraph, explain what emulsifiers do and their role in forming emulsions. Check your answers. Emulsifiers Soaps, cleansers, shampoo and detergents are all emulsifiers. This means that they all act on the surface of grease and grime to remove it. You may have observed oil floating on the surface of water. Oil molecules are not attracted to water and are less dense than water, causing oil to float as oil slicks. So how do we get greasy dishes clean? What do you add to water when washing dishes, your hair, skin or face? You add emulsifiers. Detergents, soaps, cleansers and shampoos have molecules with polar heads. This means that one end of each emulsifier is hydrophilic and attracted to water molecules; the other end is hydrophobic, repelling water, attracting it to oil molecules. Emulsifiers work on dirty dishes in the ways described below. 1 Detergent is added to warm water. The hydrophilic ends of each emulsifier are attracted to and dissolve in water. 2 The surface tension of the water is reduced, allowing water to spread over the surface of the grease on a plate. The hydrophilic ends are attracted to the water molecules and the non-polar ends are attracted to oil. 3 The hydrophobic ends of emulsifiers dissolve in the oil, helping dislodge it from the plate. 4 With some agitation, small globules of oil are lifted away from the oil on the plate. 5 Emulsifiers surround oil globules, keeping them dispersed, preventing them from joining up with other oil globules; as like electric charges repel each other. Some surfactants remain as a thin layer on the plate surface to help repel oils. Part 2: Mixing it up 19

78 Cut out the diagrams and stages in emulsifier use in Appendix 1. Stick them below in the correct order and with the correct diagram. Role of emulsifier in detergent Diagram Check your answers. 20 Part 2 Lifestyle chemistry

79 Gill Sans Bold Turn to Exercise 2.2 to model emulsification. Turn to Exercise 2.3 to prepare an emulsion and compare its properties with solutions and suspensions. Cleaning agents Cleaning agents must be both surfactants and emulsifiers. Being surfactants they concentrate at surfaces orientating their polar end in the most polar liquid and their non-polar chain in non-polar liquid. Being emulsifers, cleaning agents surround the liquid globules, keeping them dispersed and stopping them from joining up with other globules. This enables the dispersed globules to be washed away. Emulsion types Emulsion types are the colloid types that involve only liquids, that is, they are liquid-in-liquid colloids. The two most common types of liquidin-liquid colloid are oil-in-water and water-in-oil. If you just completed Exercise 2.3, you made an oil-in-water emulsion. In oil-in-water emulsions, emulsifiers act on the oil, dispersing oil through the water. In water-in-oil emulsions, the emulsifiers act on the water, dispersing water through the oil. How do you think you can tell the difference between a water-in-oil and oil-in-water emulsion? This can be done by looking at the properties of emulsions. One way is to try to conduct electricity through each emulsion. Oil molecules have a greater electrical resistance than aqueous solutions. Water-in-oil emulsions conduct electricity poorly. Oil-in-water emulsions conduct electricity much better than water-in-oil emulsions. The subject of conductivity brings us to the second method of emulsion identification. Just as water-in-oil emulsions resist conducting electricity, so too do they resist heat conduction. For this reason waterin-oil emulsions feel relatively warm to touch. Oil-in-water emulsions conduct heat quite well and feel cold to touch. Cold cream works on this principal as it conducts heat away from your body where applied. Part 2: Mixing it up 21

80 Biodegradability Have you heard the term, biodegradable? The media and advertisements often refer to biodegradability. What do you think of when you hear the term biodegradable? Write your ideas below. So what does biodegradable really mean? Is the term as green as marketing makes it appear to be? Biodegradable means an organic substance capable of being decomposed by the action of naturally occurring organisms. Almost all organic substances are biodegradable. However, some substances can take years to break down, while others take days. Biodegradable substances often break down in steps forming intermediates. Some of these intermediates can be harmful or detrimental to living organisms eg. nonylphenol is suspected to mimic hormones, disrupting normal hormonal processes in living things. 22 Part 2 Lifestyle chemistry

81 Gill Sans Bold Soaps and detergents Read the information in Appendix 2 on soaps and detergents then answer the questions following questions. 1 Draw a typical soap molecule below. 2 What substances can soap break down to form? 3 Is soap biodegradable? 4 Why was detergent produced? 5 What were first detergents made from? 6 Explain the problem associated with the first detergents. 7 What problem was associated with second generation detergents and what was the solution? 8 Do the detergents we use today contain phosphates? Explain why or why not. 9 What detergents do we use today? Are they biodegradable? Turn to Exercise 2.4 at the back of this part to discuss the biodegradability of soaps and detergents. Part 2: Mixing it up 23

82 Summary Use the clues below to fill in the missing words. The highlighted column tells you what you will learn in Part surfactants are used in these to encourage leaf coverage (two words; 12,6) 2 water repelling 3 water drops are this shape 4 an organic substance capable of being decomposed by the action of naturally occurring organisms 5 made by the reaction of a hydroxide and fat 6 attracted to water 7 the resistance of a liquid s surface to being broken (two words; 7,7) 8 surfactant with a negatively charged head 9 molecule acting on the surface of a liquid, lowering its surface tension 10 incapable of being mixed to form a homogenous solution 11 a common liquid-in-liquid emulsion 12 mixture of tiny droplets of liquid dispersed in another in which it is immiscible 13 a synthetic surfactant and emulsifier used for cleaning 24 Part 2 Lifestyle chemistry

83 Gill Sans Bold Appendix 1 Emulsifiers surround oil globules, keeping them dispersed, preventing them from joining up with other oil globules; as like electric charges repel each other. Some surfactants remain on the plate to help repel oils. The surface tension of the water is reduced, allowing water to spread over the surface of the grease on a plate. The hydrophilic ends are attracted to the water molecules and the nonpolar ends are attracted to oil. plate plate With some agitation, small globules of oil are lifted away from the oil on the plate. grease plate Detergent is added to warm water. The hydrophilic ends of each emulsifier are attracted to and dissolve in water. plate The hydrophobic ends of emulsifiers dissolve in the oil, helping dislodge it from the plate. grease plate Part 2: Mixing it up 25

84 26 Part 2 Lifestyle chemistry

85 Gill Sans Bold Appendix 2 Soaps and detergents The following information has been sourced from: Laidler, G Environmental Chemistry an Australian Perspective Second Edition. Pearson Education Australia. Soap has been used as a cleaning agent for over 4500 years. A typical soap would be sodium stearate C 17 H 35 COONa (carbon, hydrogen, oxygen and sodium), shown in the diagram below. H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H H H H H C C C C C H H H H H O C O Na+ Sodium stearate Laidler, G Environmental Chemistry An Australian Perspective Second Edition Pearson Education Australia. The part of the soap with the long carbon chain is water repelling or hydrophobic. The charged end of the soap is hydrophilic and attracts water. The soap works because the carbon chain end of the molecule dissolves in the grease or dirt, and the ionic end dissolves in the water. Soap does not function as a cleaning agent in acidic environments. Soap is made from renewable natural resource and is biodegradable, this means it can be broken down into simple molecules (CO 2, H 2 O) by bacteria in the environment. Detergents were introduced in the 1950s with better cleaning action than soap. Their synthetic make up differed from soap, which is made from the action of a hydroxide on a natural fat. These branched alkyl benzene sulfonate detergents were too slowly biodegradable, accumulating in lakes, rivers and sewage treatment works. Such detergents were responsible for frothing and bubbling in water ways in the 1960s and early 1970s. An example of these detergent molecules is shown on the following page. Part 2: Mixing it up 27

86 CH 3 CH CH 2 CH CH 2 CH CH 2 CH S O Na+ CH 3 CH 3 CH 3 represents a benzene ring CH 3 H H C C C H O O H C C C H Branched alkyl benzene sulfonate (ABS) Laidler, G Environmental Chemistry An Australian Perspective Second Edition Pearson Education Australia. New (second generation) detergents were formulated. The straight chain carbon molecules were more readily biodegradable. An example is shown below. CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH S O Na+ CH3 O Straight chain alkyl benzene sulfonate (ABS) detergent Laidler, G Environmental Chemistry An Australian Perspective Second Edition Pearson Education Australia These detergents were expensive and phosphates were added to reduce the expense. The phosphates could hold calcium, magnesium and iron ions in suspension, preventing a scum from forming. Disposal of phosphate detergents added a great deal of phosphate to water courses, causing algal blooms and eutrophication. Third generation detergents now contain straight chain ABS detergents as the active ingredient. The bulk is added in the form of sodium carbonate, sodium perborate, sodium sulfate or sodium metasilicate. They are biodegradable, taking slightly longer than soap to degrade. In domestic detergents, the surfactant molecules carry a negative charge and are called ionic surfactants eg. alkyl benzene sulfonate. Surfactant molecules can also be made with a positive charge. These surfactants are more expensive, but are antibacterial, soften fabric and are therefore used in nappy rinses and shampoos. Shampoos can also contain non-ionic and amphoteric surfactants. Soaps and detergents are emulsifying agents because they stabilise mixtures of two immiscible substances, such as oil and water, after the two liquids have been shaken together. Soaps and detergents are also surfactants (surface active agents) because they have a hydrophilic part and a hydrophobic part; this causes them to concentrate at surfaces such as between water and air or between water and oil. H O 28 Part 2 Lifestyle chemistry

87 Gill Sans Bold Suggested answers Surface tension The forces of attraction between the water molecules on the water surface cause surface area to be minimised. The surface resists any attempts to increase its surface area, thereby allowing the pin to float rather than break the water surface. Water drops on leaves 1 Water drops are a spherical shape on a leaf s surface. 2 The water molecules cling together, resisting the waxy leaf. The outermost water molecules are pulled towards the centre, therefore reducing the surface area of the water drop, causing a spherical shape. Modeling a water drop The model shows the forces between the surface water molecules and the water molecules beneath the surface. When less water molecules are below the surface, the forces between the surface molecules and those under the surface cause the surface to become spherical. (Other answers are acceptable.) Water under gravity 1 2 Falling water drops appear tear shaped because gravity causes most of the water molecules to condense towards the bottom of the drop, leaving fewer molecules at the top. (Other answers are acceptable.) Part 2: Mixing it up 29

88 Surfactants 1 anionic cationic nonionic amphoteric Emulsifiers Role of surfactant in detergent Diagram Detergent is added to warm water. The hydrophilic ends of each emulsifier are attracted to and dissolve in water. grease plate The surface tension of the water is reduced, allowing water to spread over the surface of the grease on a plate. The hydrophilic ends are attracted to the water molecules and the non-polar ends are attracted to oil. grease plate The hydrophobic ends of emulsifiers dissolve in the oil, helping dislodge it from the plate. plate With some agitation, small globules of oil are lifted away from the oil on the plate. plate Emulsifiers surround oil globules, keeping them dispersed, preventing them from joining up with other oil globules; as like electric charges repel each other. Some surfactants remain on the plate to help repel oils. plate 30 Part 2 Lifestyle chemistry

89 Gill Sans Bold Understanding emulsification 1 An example analogy is: a group of star wars fighter craft represent oil. They are attacked and broken up by enemy fighters. The enemy fighters represent emulsifiers. The enemy surround small groups of star wars fighters, preventing them from forming a group. The star wars fighter crafts are effectively emulsified. 2 Cleaning agents must be surfactants to wet surfaces for dirt and grease removal. They must also be emulsifiers to keep dirt and grease from re-accumulating and re-coating surfaces. 3 Emulsifiers for example break up immiscible substances into smaller globules and hold the globules in suspension in another liquid. Soaps and detergents 1 H H C H H C H H C H H C H Soap molecule. H C H H C H H C H H C H H C H H C H H C H H C H H H H H H C C C C C H H H H H O C O Na+ 2 Soap can break down to form CO 2 and H 2 O. 3 Soap is biodegradable, breaking down within several days. 4 Detergent was produced to clean more thoroughly and function in acidic environments. 5 The first detergents were made from alkyl benzene sulfonates. 6 The first detergents were too slowly biodegradable in the environment. 7 Second generation detergents were costly. Adding phosphates reduced the amount required for cleaning. 8 Today s detergents do not contain phosphates because phosphates added nutrient to water courses, causing algal blooms. 9 Today s detergents are straight chain alkyl benzene sulfonates (ABS) which are biodegradable, taking slightly longer than soap to break down. Summary Answers provided on the following page. Summary Part 2: Mixing it up 31

90 1 A G R I C U L T U R A L S P R A Y S 2 H Y D R O P H O B I C 3 S P H E R I C A L 4 B I O D E G R A D A B L E 5 S O A P 6 H Y D R O P H I L I C 7 S U R F A C E T E N S I O N 8 A N I O N I C 9 S U R F A C T A N T 10 I M M I S C I B L E 11 M I L K 12 E M U L S I O N 13 D E T E R G E N T 32 Part 2 Lifestyle chemistry

91 Gill Sans Bold Exercises - Part 2 Exercises 2.1 to 2.4 Name: Exercise Observe a small amount of water in a small drinking glass. Draw and label the glass and the meniscus below. 2 Pour a small amount of oil in a small, dry glass. Draw and label the glass and the meniscus below. Refer to the Science Resource Book if you are unsure how to draw equipment scientifically. This exercise continues on the next page. Part 2: Mixing it up 33

92 3 Compare the strength of the adhesive force between water and glass with the strength of the adhesive force between oil and glass. _ 4 Justify the conclusion that the adhesive forces between water and glass are stronger than the cohesive forces between water molecules. Exercise 2.2 You should have jellybeans, snakes and toothpicks left over from a previous experiment. You will need: 2 snakes cut up into approximately 1 cm pieces (16 pieces in total) 4 jelly beans 16 toothpicks. Follow the following steps to carry out the activity. 1 Draw a negative symbol - at one end of each of the 16 toothpicks. The toothpicks represent anionic surfactants or emulsifiers with a negative polar head. Negative polar heads are attracted to water. The 16 pieces of snake represent water molecules. 2 Stick a piece of snake on the polar (negative) end of each toothpick. The result should be 16 surfactants (toothpicks) with their negative polar heads buried in water (pieces of snake). Draw one toothpick and snake pieces at this stage. Label the toothpick as an emulsifier and the snake pieces as water molecules. 34 Part 2 Lifestyle chemistry

93 Gill Sans Bold 3 Line up the four jellybeans end to end in a row. Their ends should be touching. This represents oil smeared on a plate. Draw your jelly beans below. Label them as an oil slick. 4 The non-polar end of each emulsifier is attracted to oil. Stick the non-polar end of a toothpick into a jellybean. Repeat this with the other three jellybeans. The result should be four toothpicks (emulsifiers) with their polar heads buried in pieces of snake (water) and their non-polar tails buried in jelly beans (oil). The jelly beans should be arranged the same as in step 3. Draw your model at this stage (you should have used only four of your sixteen toothpicks). Imagine you agitate the oil, just as you do as you wash up dishes. The agitation allows emulsifiers to surround the oil, breaking it into oil globules. Part 2: Mixing it up 35

94 5 Each jellybean represents an oil globule. Separate the four jelly beans, sticking four toothpicks into each jellybean. Each oil globule should be surrounded with toothpicks (emulsifiers). If you have ever played with magnets, you will know that two negative ends repel each other. This is exactly what happens to the negatively charged heads of emulsifiers. The repelling action prevents the surfactants from sticking together. For this reason, the oil globules they are holding are unable to join together. It is the repelling quality of charged emulsifiers that make them capable of holding immiscible substances in suspension eg. oil in water. 6 On the diagram below: label the toothpicks as emulsifiers, the jelly beans as oil globules and the snake pieces as water draw the negative charges where they belong on one end of each toothpicks (emulsifiers) draw the repelling forces between the negative ends of toothpicks (emulsifiers). Zig-zag lines might represent this well. Model representing emulsified oil. 36 Part 2 Lifestyle chemistry

95 Gill Sans Bold Exercise 2.3 You will now make your own emulsion. Half fill a glass jar with warm water. Place a small amount of any oil in the water and a small amount of detergent. Place the lid on the jar and shake. You have just made an emulsion. Tiny oil globules are held inside the liquid by the action of the emulsifiers in the detergent. Test the oil-in-water emulsion for the characteristics listed in the table below. If the characteristic is present the box. If the characteristic is not present the box. You may need to make similar observations to those made in Exercise 1.2. Characteristic Solution Suspension Oil-in-water emulsion settling of particles residue is left after filtering light beam shone through the mixture seen in the mixture 1 How did you determine if particles did or did not settle in the oil-in-water emulsion? 2 How did you determine if residue was left after filtering? 3 How did you determine if a light beam could be seen in the emulsion? 4 Explain the different properties of a solution, a suspension and an emulsion by using the information in the table above. Part 2: Mixing it up 37

96 5 Refer to Part 1 and compare the properties of a colloid with those of the emulsion in your table. Were they the same? Finish the following sentence: An oil in water emulsion is a Exercise 2.4 Read through Appendix 2 before attempting this exercise. Compare the biodegradability of soaps to first, second and third generation detergents. Present your answer as a scientific discussion. (Use present or past tense language.) 38 Part 2 Lifestyle chemistry

97 Gill Sans Bold Senior Science HSC course Stage 6 Lifestyle chemistry Part 3: Your skin IncorporatingOctober2002 AMENDMENTS

98 Senior Science Stage 6 HSC Course Lifestyle Chemistry The substances you use Mixing it up Your skin What s growing on your skin? Dissolve it! Good medicine Medical Technology Bionics Information Systems Option

99 Gill Sans Bold Contents Introduction... 2 The role of skin... 3 Investigating skin...6 Hygiene products... 8 Open ended investigation Summary Appendix Appendix Appendix Appendix Suggested answers Exercises Part Part 3: Your skin 1

100 Introduction In Part 3 you will be given the opportunity to identify the three main roles of skin, identify the parts of the skin and the common components of products used on the skin. In Part 3 you will be given opportunities to learn to: identify the role of the skin as an organ to separate the body from the external environment an organ assisting in body temperature control an organ to protect against entry by disease-causing organisms identify and explain the use of common components of body soaps, cleansers and shampoos and the reason for their use In Part 3 you will be given opportunities to: perform a first-hand investigation to examine prepared slides of human skin identify data sources, plan, choose equipment or resources for, and perform a first-hand investigation to test a manufacturers claim(s) on a commercial product such as soap, shampoo or shower gel and use the available evidence to analyse the results and discuss the validity of the claim(s) Extract from Senior Science Stage 6 Syllabus Board of Studies NSW, October The most up-to-date version is to be found at 2 Lifestyle chemistry

101 Gill Sans Bold The role of skin The skin is the largest organ in your body. It covers you from head to toe. Have you ever been frustrated with your skin s appearance: pimples, freckles, tan, lack of tan, dryness, stretch marks, sun burn, birth marks and moles? When you discover the many functions of skin in maintaining your health, you may feel differently about your skin. Record as many functions of your skin as you can think of eg. protecting your body tissues. The majority of information on skin is delivered on the audio tape Skin. You are required to listen to each section before carrying out activities on the following pages. Listen to the Role of skin section of the Skin audio tape or internet audio files (at go to Senior Science, go to Lifestyle Chemistry) and summarise the role of the skin under each of the headings below. (Answers are not provided to questions 1-3 to encourage you to complete your summaries.) 1 Barrier Part 3: Your skin 3

102 2 Protection from disease 4 Temperature control 5 Listen to the Skin structures section of the Skin audio tape/internet audio files to correctly label the diagram below. Cross section of human skin 4 Lifestyle chemistry

103 Gill Sans Bold 6 Listen again to the same audio section that you used to label the diagram on the previous page. Use the information to fill in the blank spaces in the structure and function table for parts of human skin below. Structure Function top layers of the skin, protects the underlying tissue; forms a barrier from heat loss, water loss and micro-organisms sweat gland traps heat on the surface of the skin hair bulb the under skin section of hair muscles dermis produces and injects melanin into surrounding cells for skin pigmentation fibroblasts subcutaneous layer produces oils to lubricate the hair and skin sweat is released alongside coarse hair to help with evaporation Check your answers. Turn to Exercise 3.1 to explain the three primary functions of the skin. Part 3: Your skin 5

104 Investigating skin Focusing a microscope Do you remember how to correctly focus a microscope? Appendix 1 outlines the steps involved in focusing a microscope and a labelled diagram of a light microscope for your review. You are required to examine a prepared slide of human skin. To do this you will need to correctly focus a microscope or at least know how if you do not have access to a microscope. Turn to Appendix 2. Cut out the steps involved in focusing a microscope which appear in an incorrect order. Arrange the steps for focusing a microscope in the correct order according to Appendix 1 and stick them in the table below. (If you remember how to focus a microscope, you may not need to refer to Appendix 1.) Order Focusing a microscope Check your answers. 6 Lifestyle chemistry

105 Gill Sans Bold Viewing a prepared slide You are required to examine a prepared slide of human skin. If you have a microscope at home, your teacher may send you a prepared slide of human skin for you to complete Exercise 3.2a. If you do not have access to a microscope, it is suggested that you complete Exercise 3.2b. However, it is suggested you view a prepared slide when on site with your teacher. Turn to Exercise 3.2a or 3.2b at the back of this part to draw and label a prepared slide of human skin tissue. Complete Exercise 3.3, stating the functions of parts identified in Exercise 3.2. Part 3: Your skin 7

106 Hygiene products How often do you use body soap or shampoo? Do you use a facial cleanser or do you know someone who does? Are they all emulsifiers? Do you know what they are made of? Soaps, shampoos and cleansers all contain emulsifying agents. Their primary functions are to lift away oils and other contaminants, just as described in Part 2. However, the components of shampoos, soaps and cleansers can differ greatly. General ingredients in shampoos, soaps and cleansers are displayed in the Appendix 4. You are to compare your shampoo, cleanser and soap ingredients to those listed in Appendix 4. You will need a list of ingredients for the shampoo; soap; and cleanser you use at home. If you do not have these products at home or the package listing the ingredients, choose a brand of each at the supermarket to complete the following questions or ask friends or neighbors for help. You will not need to buy these products. Simply answer the questions based on the labels. Ingredients are listed from most to least in volume used. If you buy biscuits with the first ingredient as vegetable oil, you can be assured the biscuits are fatty. The last ingredient on the ingredients list has the least volume in the product eg. spices in biscuits. The exception to this is water. 1 Compare the ingredients of your shampoo with those in the Appendix 4. Record the ingredients in your shampoo that are the same as those listed in Appendix 4: Main constituents of shampoo. 2 Use the information in Appendix 4 to state the functions of each of the ingredients listed above. 8 Lifestyle chemistry

107 Gill Sans Bold 3 Did your shampoo contain many other ingredients not listed in the Appendix 4? Why do you think this is? Many different substances can do similar things. Companies producing hygiene products rely on this to create new shampoos with different qualities. In each instance however, the function of a shampoo is to emulsify oils and other contaminants, removing them from the hair and scalp safely with no harmful effects. 4 List the ingredients in a cake of body soap at home. 5 Refer to the Appendix 4: Main constituents of soap to record the function of the ingredients above. 6 Does your soap contain substances that are not in the Appendix 4? 7 What functions do you think each of these other substances have? 8 List the ingredients in your cleanser that are also listed in the Appendix 2 under Main constituents of cleansers. Cleansers often contain many other substances to support claims such as: antibacterial qualities, make-up removal, deep cleansing, non-drying, moisturising, exfoliating and many more. Part 3: Your skin 9

108 1 List the ingredient(s) that are common to cleansers and shampoos. 2 What are the functions of these ingredients? _ Soaps act in a similar way to the detergents you outlined above. They are both emulsifiers. 3 What are the main functions of shampoos, soaps and cleansers? Check your answers. Manufacturers advertise desirable qualities in their hygiene products such as: extra body shampoos, everyday use shampoos, colour protective shampoos and pro-v shampoos for improving hair quality. You can probably think of many more. Cleansers and soap manufacturers make other claims to help sell their products. 10 Lifestyle chemistry

109 Gill Sans Bold Open-ended investigation You are required to carry out at least one open-ended investigation during the HSC Senior Science course. In doing so, you must integrate and demonstrate skills, knowledge and understanding. This might sound difficult, but each time you design and carry out an experiment, you are demonstrating skills and each time you draw conclusions based on your results and knowledge, you are demonstrating understanding. This particular open-ended investigation will be fun. You are about to test the claims of a skin product or a product that comes in contact with the skin or hair. This investigation is the largest and most detailed investigation you will plan, carry out and report on in Senior Science this year. Your teacher may use this open-ended investigation as an assessment task. Think about the products in your home. Is there a shampoo that makes a claim that you have always wanted to test like improved styling. Have you always wanted to test those soaps that claim to moisturise your skin? Does your dishwashing liquid really lift grease well? Do skin firming moisturisers really make your skin firm? Can you think of a commercial product such as soap, shampoo or shower gel, that comes in contact with the skin or hair that you could test? If you cannot think of any, ask friends and family. You may need to test the product against another (or several others) to gain results eg. a no-name soap against Dove soap; a pro-v shampoo against Pears shampoo. Alternative methodology could be for several people or subjects to use the product. Their observations with regards to the manufacturer s claims can form your results. Your investigation How you approach, plan and present your investigation is for you to decide. However, the use of headings such as: aim; apparatus; method; results; discussion; and conclusion, is strongly recommended as a framework for your scientific report. Part 3: Your skin 11

110 In this section you will only plan your investigation. It is suggested you plan your investigation in draft first before recording your plan for Exercise 3.4. Your plan should be sent to your teacher for review. When your teacher is satisfied with your plan, you may begin your investigation. Your completed open-ended investigation should be handed in with Part 6, unless another date is specified by your teacher. Be aware that your teacher may use this open-ended investigation as an assessment task. It is essential that you contact your teacher as you complete Part 4 to gain permission to go ahead with your plan and carry out your investigation. Remember, you must submit your completed open-ended investigation with Part 6 unless your teacher specifies a different date. The time taken to complete the investigation is not included as part of this module. Your open-ended investigation is homework. Parts 4, 5 and 6 will contain the following reminder:? What progress have you made towards your open-ended investigation from Part 3? Your report must be submitted with Part 6 or by a date specified by your teacher. This reminder should prompt you to call your teacher to gain approval to start your investigation, allowing enough time to complete the investigation at the conclusion of Part 6. Ideas to think about When planning the investigation keep these questions in mind. Will you test the product on several people? How long will you need for results to be measurable? 12 Lifestyle chemistry

111 Gill Sans Bold How often will you test the product eg. five times a day or once only? Will you test several different products and compare their effects? How will you assess if the product does or doesn t stand up to its claims; will you record people s comments on the product use, or measure results such as relative hair volumes? How will you present your results? Will you graph your results or include photographs? How will you ensure the variables remain constant such as the same volume of shampoo, the same hair types (ie. straight hair) and the same amount of rinsing time? When you complete your discussion and draw your conclusions, will you: outline your results, relating them to what you have learned about solutions, colloids, suspensions and emulsions and skin structure relate your results to the ingredients in the substance tested add additional information you have found on similar products suggest improvements to your experimental procedure suggest reasons for the experiment not working suggest further investigations that could be carried out? When presenting your report, take these suggestions into account. Remember to use scientific language in your investigation. Don t be afraid to include pictures, diagrams, graphs and tables. Contact your teacher as soon as you need help. Refer to the Science Resource Book or contact your teacher if you re not sure how to approach the discussion and conclusion. Enjoy the activity. Turn to Exercise 3.4 at the back of this part to record your plan for your open-ended investigation. Part 3: Your skin 13

112 Summary Briefly write what you have learned under each syllabus point below. Extracts from Senior Science Stage 6 Syllabus Board of Studies NSW, originally issued The most up-to-date version is to be found at identify the role of the skin as: an organ to separate the body from the external environment _ an organ assisting in body temperature control _ an organ to protect against entry by disease-causing organisms _ identify and explain the use of common components of body soaps, cleansers and shampoos and the reason for their use _ 14 Lifestyle chemistry

113 Gill Sans Bold perform a first-hand investigation to examine prepared slides of human skin. (This section is left blank for you to draw a diagram.) identify data sources, plan, choose equipment or resources for, and perform a first-hand investigation to test a manufacturers claim(s) on a commercial product such as soap, shampoo or shower gel and use the available evidence to analyse the results and discuss the validity of the claim(s). Part 3: Your skin 15

114 16 Lifestyle chemistry

115 Gill Sans Bold Appendix 1 Focusing a microscope eyepiece tube nosepiece objective lens stage clip stage condenser coarse focus knob fine focus knob mirror condenser adjustment knob Light microscope. 1 Plug in and turn on a lamp. 2 Face the lamp to the mirror. 3 Turn the nosepiece to set the objective lens on required magnification eg. x10. 4 Look down the tube through the eyepiece and adjust the mirror to allow sufficient light through the tube. 5 Place a prepared slide on the stage, clipping it into place with stage clips. 6 While looking from the side, wind down the tube using the coarse focus knob till the objective lens is almost touching the slide. Part 3: Your skin 17

116 7 Look through the eyepiece, down the tube and slowly wind back the coarse focus knob until the image comes into focus. If an image is not seen, steps 6 and 7 should be repeated. 8 Adjust the fine focus knob to clearly focus the image. 18 Lifestyle chemistry

117 Gill Sans Bold Appendix 2 Cut out the following steps involved in focusing a microscope and stick them in the correct order on page 6. Adjust the fine focus knob to clearly focus the image. Turn the nosepiece to set the objective lens on required magnification eg. x10. Plug in and turn on a lamp. Place a prepared slide on the stage, clipping it into place with stage clips. Look through the eyepiece, down the tube and slowly wind back the coarse focus knob until the image comes into focus. While looking from the side, wind down the tube using the coarse focus knob till the objective lens is almost touching the slide. Look down the tube through the eyepiece and adjust the mirror to allow enough light through the tube. Face the lamp to the mirror. Part 3: Your skin 19

118 20 Lifestyle chemistry

119 Gill Sans Bold Appendix 3 Cross section of human skin as seen under a light microscope. Magniification x 100 (Scanned from a prepared slide Selby. Australia.) Part 3: Your skin 21

120 22 Lifestyle chemistry

121 Gill Sans Bold Appendix 4 Main constituents of shampoo Ingredient methylparaben lauramide DEA hydrolysed animal protein propylparaben cocamide DEA ammonium lauryl sulfate sodium lauryl sulfate triethanolamine lauryl sulfate propylene glycol sodium laureth sulfate glycol stearate hydroypropyl methyl cellulose quanternium - 15 imidazolidinyl urea amphoteric 2 DMDM hydantoin panthenol Function preservative foam stabiliser conditioner/stabiliser preservative foam booster detergent detergent detergent coupling agent detergent thickener/pearling agent thickener conditioner antimicrobial detergent/conditioner antimicrobial vitamin source ICI Australia, Chemical Fact Sheets, ICI Australia, Melbourne. Part 3: Your skin 23

122 Main constituents of soap Ingredient Function oil (palm oil) sodium hydroxide glycerine (glycerol) water sodium chloride fragrance reacts with sodium hydroxide to form soap and glycerol reacts with oil to form soap and glycerol formed in the reaction of sodium hydroxide and oil; thickener used to rinse the soap separates glycerol from the soap fragrance Other substances are present or absent in different soaps to alter texture; give foaming action; moisturise; have antibacterial qualities; impart odour; act as abrasives; act as preservatives and many more. Shower gels and liquid soaps contain similar ingredients to cleansers. Main constituents of cleansers Ingredient Function water sodium lauryl sulfate cocamide DEA (and many other varieties) solvent detergent foam booster glycerine citric or lactic acid fragrance thickener ph balance fragrance Other substances are present or absent in different cleansers to alter texture; give foaming action; moisturise; have antibacterial qualities; impart odour; act as abrasives and many more. 24 Lifestyle chemistry

123 Gill Sans Bold Suggested answers The role of skin 5 hair opening of sweat gland sebaceous gland opening sebaceous gland melanocyte basal layer apocrine sweat gland epidermis muscle that pulls on the hair hair follicle dermis hair bulb subcutaneous layer nerve fibre vein artery Labeled cross section of human skin. eccrine sweat gland Part 3: Your skin 25

124 6 Structure Function/s epidermis sweat gland hair hair bulb hair follicle muscles dermis melanocyte fibroblasts subcutaneous layer sebaceous gland apocrine gland top layers of the skin, protects the underlying tissue; forms a barrier from heat loss, water loss and microorganisms to excrete saline water, releasing body heat through evaporation of sweat traps heat on the surface of the skin site of hair growth the under skin section of hair cause hair to become erect, trapping warm air close to the surface of the skin, helping temperature regulation middle layer containing skin fibres produces and injects melanin into surrounding cells for skin pigmentation maintains skin elasticity consists of larger connecting veins and arteries and fatty tissue to help insulate the body produces oils to lubricate the hair and skin sweat is released alongside coarse hair to help with evaporation. 26 Lifestyle chemistry

125 Gill Sans Bold Focusing a microscope Focusing a microscope 1 Plug in and turn on a lamp. 2 Face the lamp to the mirror 3 Turn the nosepiece to set the objective lens on required magnification eg. x10. 4 Look down the tube through the eyepiece and adjust the mirror to allow sufficient light through the tube. 5 Place a prepared slide on the stage, clipping it into place with stage clips. 6 While looking from the side, wind down the tube using the coarse focus knob till the objective lens is almost touching the slide. 7 Look through the eyepiece, down the tube and slowly wind back the coarse focus knob until the image comes into focus. If an image is not seen, steps 6 and 7 should be repeated. 8 Adjust the fine focus knob to clearly focus the image. Hygiene products 1 Ingredients common to cleansers and shampoos are: sodium lauryl sulfate and cocamide DEA. 2 Sodium lauryl sulfate is a detergent and cocamide DEA is a foam booster. 3 The main functions of shampoo, soap and detergents are to emulsify dirt and oils and remove them from the surface of skin or hair. Part 3: Your skin 27

126 28 Lifestyle chemistry

127 Gill Sans Bold Exercises - Part 3 Exercises 3.1 to 3.3 Name: Exercise 3.1 There are three main functions of skin. Provide a brief and concise description of these three functions Exercise 3.2 You must complete Exercise 3.2a if you have a microscope or 3.2b if you do not have access to a microscope. Each activity is outlined on the following page. Exercise 3.2a 1 Focus a prepared slide of a cross section of human skin tissue on x100 magnification (this is x10 objective lens combined with the x10 magnification of the eyepiece). Part 3: Your skin 29

128 2 Clearly draw what you see in the circle below. If you are unsure how to present your drawing and in what detail, refer to the Science Resource Book or contact your teacher. 3 Use the labeled diagram of the skin on page 25 to identify and label your diagram of human skin tissue. 4 Write a title for the diagram and record its magnification next to the cross on the bottom right corner. Exercise 3.2b 1 Observe the diagram of a prepared cross section of human skin tissue under x100 magnification in Appendix 3. 2 Clearly draw what you see in the circle below. If you are not sure how to present your drawing, and in what detail, refer to the Science Resource Book or contact your teacher. 3 Use the labeled diagram of the skin on page 25 to identify and label your diagram of skin tissue. 4 Write a heading for the diagram and record its magnification next to the cross on the bottom right corner. 30 Lifestyle chemistry

129 Gill Sans Bold Exercise 3.3 Each part of human skin has a function. For three labels indicated in Exercise 3.2, state their functions below. Part Function Exercise 3.4 Plan your open-ended investigation below. You should make a rough copy on separate paper first. Include attachments with this exercise if this section is not large enough for your plan. Keep a copy of your plan for you to follow as you carry out your experiment over the coming weeks. Perhaps you could keep a journal. Aim What are you trying to find out? What product(s) are you testing? Part 3: Your skin 31

130 Apparatus What and or who will you need to carry out your investigation? Method How will you carry out your investigation? Organise each step sequentially and either number or dot point the steps. How will you collect results? Will your data be quantitative (measured) or qualitative (compared against each other)? Indicate your dependent and independent variables. Outline how you will ensure controlled variables are kept constant and what your control will be. It is essential these points are covered. If you are unsure of these terms refer to the Science Resource Book or contact your teacher. 32 Lifestyle chemistry

131 Gill Sans Bold Results How will you present your results? Will you use a table? Will you include photographs or draw a graph? Include a plan showing how you will record your results. You may include a rough sketch of a graph you are expecting to draw. You must indicate if your results are to be quantitative (measured) or qualitative (compared against each other). If you do not understand the meaning of these terms, refer to the Science Resource Book or contact your teacher. Don t forget to keep a copy of your plan. You will need to follow it while conducting your open-ended investigation. Part 3: Your skin 33

132 Gill Sans Bold Senior Science HSC course Stage 6 Lifestyle chemistry Part 4: What s growing on your skin? IncorporatingOctober2002 AMENDMENTS

133 Senior Science Stage 6 HSC Course Lifestyle Chemistry The substances you use Mixing it up Your skin What s growing on your skin? Dissolve it! Good medicine Medical Technology Bionics Information Systems Option

134 Gill Sans Bold Contents Introduction... 2 The microflora of skin... 3 Microbe colonisation...9 Breaking the barrier...10 Acidity and alkalinity The ph scale...12 The ph of skin Skin and hair products...16 Testing skin and hair products...17 Summary Appendix Appendix Suggested answers Exercises Part Part 4: What s growing on your skin? 1

135 Introduction Your skin is host to a great number of micro-organisms. They live on skin oils, proteins and sweat. Your first instinct might be Yuck! Get rid of them! However, these microbes play an important role in body defence. The skin and hair products you use must be compatible with the skin s natural defense or damage and infections can result. In Part 4, you will be given the opportunities to learn to: define the term microflora and discuss the role of the microflora on skin in different parts of the body discuss the term ph in terms of its ability to describe the acidity of a substance explain the relationship between the natural ph of the skin and the action of microflora natural oil produced by glands in the skin perspiration. In Part 4, you will be given opportunities to: perform first-hand investigations to measure the ph values of a range of skin and hair products. Extract from Senior Science Stage 6 Syllabus Board of Studies NSW, October The most up-to-date version is to be found at 2 Lifestyle chemistry

136 Gill Sans Bold The microflora of skin The term microflora is an odd term. You should understand the term micro. It means very small or microscopic in size. You are not able to see micro-organisms with the naked eye. The second part of the term microflora is flora. What would you normally associate the term flora with? Think about florists, floral patterns, flora and fauna. Have you decided what flora should mean? Your answer should have been plants. Automatically your brain should think that microflora means microscopic plants, right? Wrong! In this instance, flora appears to take on the meaning of an ecosystem or a group of organisms surviving together. For this reason, the term microflora is defined as microorganisms surviving as microscopic communities. 1 Write the correct definition for microflora in the box below. Your mouth, nose and ears all contain different varieties of microflora. Most microflora on and in the body are bacteria. You will be researching the natural microflora existing on the surface of your skin and what their effects are. Part 4: What s growing on your skin? 3

137 2 Use the glossary to define the following terms as they will help you understand the Microflora section of the Skin audio tape/internet audio files. bacteria staphylococci cocci microbes micro-organisms sebum epidermis keratin Think about the skin on different parts of your body. Colour the parts of the body below where you think bacteria might exist. Remember, you are focusing on where bacteria might exist on the surface of your skin. 4 Lifestyle chemistry

138 Gill Sans Bold You will see how accurate your predictions were as you listen to the following audio. Listen to the Microflora section of the Skin audio tape/internet audio files, then carry out the activities which follow. You may need to listen to the tape several times in order to answer all the questions. 3 Why is skin not considered to be uniform? 4 What conditions favour the growth of micro-organisms? 5 All organisms require nutrients to live. What nutrients are available on the skin surface for micro-organisms to utilise? 6 Why is the skin an unstable site for microbes to colonise? 7 What effects can the action of microflora have on the skin surface? Appendix 1 contains a species list of microflora found on the surface of human skin. Use this list to help you spell the species names stated in the audiotape for the following question. Word processed genus and species names are italicized eg. Staphylococcus aureus. The first name is the genus name and must start with a capital letter. The second name is the species name and begins with a lower case letter. You might remember from preliminary work that when hand writing genus and species names, you must underline each separately eg. Staphylococcus aureus. Do this for the species column for question 8 on the following page. Part 4: What s growing on your skin? 5

139 8 List the species of microflora in the table below and indicate where they are commonly found on the body. Disregard the centre column as you will complete this with question 9. The first one has been done for you. Species of microflora Group Part of body found Staphylococcus epidermidis upper body 9 Classify each of the micro-organisms identified above into groups. The classifications are: bacteria, fungi and mites. Write these names in the middle column in the above table. All cocci and bacilli are forms of bacteria. Mould and yeast are forms of fungus. Refer to Appendix 1 to help you classify each species. 10 Look at the diagrams of cocci, bacilli and moulds on the following page, then answer the following questions. 6 Lifestyle chemistry

140 Gill Sans Bold coccus diplococcus staphlococcus Examples of cocci bacteria viewed under a high powered microscope. Examples of bacilli bacterium under a high powered microscope. Example of a mould under a light microscope (not as high powered). 10 a) What do the diagrams of cocci bacterium look like to you? b) Describe what bacilli look like in one sentence. Part 4: What s growing on your skin? 7

141 c) Explain the difference between moulds and bacteria when viewed under a microscope. 11 For each of the body parts inhabited by microflora in question 8, indicate the microflora present on the diagram of a person on the following page. The places where particular species of microbes are found on human skin. Check your answers. 8 Lifestyle chemistry

142 Gill Sans Bold Microbe colonisation More recent studies have found that microflora of the skin can be divided into two groups: resident microflora and transient microflora. Resident microflora are found on the skin surface and are thought to reside in the sebaceous glands under the skin. Bacterial counts are higher where more oil is being produced by sebaceous gland activity. Resident bacteria such as Staphylococcus epidermidis are thought to play an important role in protecting the individual from more pathogenic or disease-causing bacteria. It has been found that an area of skin colonized by relatively harmless bacteria inhibits the growth of other microbes. In this way, the body is protected from skin diseases and disorders by the microbes living on the skin surface. Transient microflora have two sources. The first source is the external environment eg. soil, water and air. Contact with soil, water and air transfers any microbes present to the skin surface. The second source is the natural microflora that comes out of body orifices such as the nasal passages, ear canals and anus. Micro-organisms are transferred to various parts of the body by the hands. Once these organisms are transferred to a suitable site, they can flourish. Transient microbes can cause diseases such as diarrhoea and meningitis. Washing with soaps and detergents removes many surface microbes, along with a great deal of the oily protective layer. However the remaining resident microbes quickly grow and reproduce to colonise the clean skin, restoring the natural microflora of the skin. Part 4: What s growing on your skin? 9

143 Breaking the barrier Have you ever had a rash or skin irritation? Your skin defence could have been breached. Have you ever had tinea on your feet? If so, your skin defence has been breached. There are many ways your skin defense can be broken. You may have recently broken your skin defense barrier without realising. Have you burnt or cut yourself recently? You may have shaved an area of skin; grazed yourself; or handled chemicals such as turps without gloves. All these common activities can alter the protective layer of skin. A change in diet can cause a change in skin acidity, lowering your defense to harmful micro-organisms. Even washing can remove natural microflora, allowing more harmful microbes to colonise the area. Has your skin become damaged over the last two weeks? Record the damage, how it occurred, the part of the body and any resultant infections or skin irritations that occurred. Damage to skin How the skin was damaged Part of the body Resulting infections or irritations As you have seen, the protective skin barrier is easily damaged. Harmful microbes living on the skin surface can easily penetrate a wound, causing an infection. The use of products that are incompatible with the skin surface can cause skin damage, alter the natural acidity of the skin or alter the natural microflora of the skin. 10 Lifestyle chemistry

144 Gill Sans Bold Acidity and alkalinity Carry out the following activity to review ph in terms of acidity and alkalinity. 1 a) Write the numbers 0 to 14 on the scale below. b) On the line next to 7, after the arrow, write neutral ph. c) On the line next to 1, write strongly acidic. d) On the line next to 14, write strongly alkaline. e) Next to the arrow pointing up, write increasing acidity. f) Next to the arrow pointing down, write increasing alkalinity. 0 Æ Ø 14 Well done. You just created a ph scale. Part 4: What s growing on your skin? 11

145 The ph scale measures acidity and alkalinity from 0 to 14. From the previous activity you should understand that a ph number lower than 7 indicates an acid and a number greater than 7 indicates an alkali. A ph of 7 is neutral. Most organisms prefer to live in ph neutral conditions (7) as acids and alkalis tend to damage cells and destroy tissue. A ph of 4 is more acidic than a ph of 6. A ph of 10 is less alkaline than a ph of 12. The stronger the acid or alkali, the more dangerous it is as it has the ability to corrode substances. 0-2 is a strongly acidic; 3-4 is an acid; 5-6 is weakly acidic; 7 is neutral; 8-9 is weakly alkaline; is alkaline; and is strongly alkaline solution. 2 Indicate the acidity or alkalinity of the following ph values using the above information. a) 4 b) 6 c) 13 d) 10 e) 7 f) 9 g) 1 Check your answers. The ph scale You may have received some ph paper from your teacher with this part. ph paper turns a different colour depending on the acidity or alkalinity of the substance it is testing. You will be investigating the ph range You will need to match your ph paper with a colour to determine the ph of the substance you are testing. 12 Lifestyle chemistry

146 Gill Sans Bold You are about to create a colour scale by which you can gauge colour changes in the ph paper. Use coloured pencils or textas to colour in the blank boxes below with the shade indicated below each box. You may need two different colours to create the correct shade in each box. Colour maroon red deep orange orange light orange yellow/mustard light green grass green dark green deep blue/green dark blue Shade ph You will be using the colour scale you just made for experiments later in this part. You may need some practice to read the correct ph from the scale and determine if it indicates acidity or alkalinity or neutrality. State the ph of the following shades of ph paper and the acidity or alkalinity they indicate. You may use the boxed information on page 12 to help you determine acidity and alkalinity. The first one has been done for you as a guide. Shade of ph paper ph Acidic/alkaline dark green 9 weakly alkaline orange deep blue/green deep orange light green maroon yellow/mustard Check your answers. Part 4: What s growing on your skin? 13

147 The ph of skin Do you recall seeing lipsticks in shops that are green or blue, but change colour when you apply them? The lipsticks change colour due to the acidity of the skin. Often two people can apply the same lipstick, but it will turn a different colour on each person due to the different acidity levels of each person s skin. This lipstick is not to be confused with normal lipstick which stays the same colour when applied. Many factors can affect the ph of your skin. Listen to the Skin ph section of the Skin audiotape/internet audio files. You may need to listen to the tape several times to answer the following questions. 1 What is the normal ph range of human skin? 2 Explain the normal ph range in terms of acidity and alkalinity eg. strongly acidic to alkaline. _ 3 What main factor causes skin to become acidic? 4 What parts of the body have different ph values? 14 Lifestyle chemistry

148 Gill Sans Bold 5 Are the ph values that are commonly associated with the parts of the body outlined in question 4 higher or lower than the rest of the body? Does this mean they are more acidic, more neutral or more alkaline? 6 Are more or fewer microbes associated with the underarms, forehead, toe webs and the soles of the feet? 7 There are two theories why the underarms, forehead, toe webs and the soles of the feet have higher ph values. Explain those two theories below. a) b) 8 What is the acid mantle? 9 What is thought to be the function of the acid mantle? 10 Some scientists believe that the acid mantle has little to do with the microflora of skin. What do they suggest has a greater impact on microbe populations on the skin surface? Check your answers. Part 4: What s growing on your skin? 15

149 Turn to Exercise 4.1 at the back of this part to discuss the role of microflora in different parts of the body.? What progress have you made towards your open-ended investigation from Part 3? Your report must be submitted with Part 6 or by a date specified by your teacher. Skin and hair products 1 Fill in the missing words in the passage below. Imagine you are a microbe living on a person s face. You are comfortable living with a ph of 6. Suddenly, the person their face with a substance that has a ph of 8. The skin has changed from weakly to weakly. You and your friends cannot survive above a ph of 7.5. You die, along with your friends. The skin surface is no longer acidic. The mantle has been altered. Different are more able to colonise the area you were living on. They may cause on the skin surface. Write the questions for the following answers. 2 Your clean skin could become colonised by different, microbes if the ph was changed. These microbes could cause disease. 3 Products used on the skin should have a similar ph to that of skin to minimise disruption of the acid mantle. The acid mantle protects the skin from colonisation by harmful organisms. 4 Substances that are acidic or alkaline have the ability to destroy living tissue. Products used on the skin with a ph below 5 or above 9 have the ability to damage the skin. The protective layer of skin can allow the entry of harmful organisms once damaged. Rashes, skin irritations, infections and disease can result. Check your answers. 16 Lifestyle chemistry

150 Gill Sans Bold Testing skin and hair products 1 Next to the bullet points below, write down all the skin and hair products you have at home. Include as many as you can such as: soaps; cleansers; shampoos; deodorant, hair spray; ointments; heat rub; shaving cream; moisturisers; perfume; sunscreen after shave; and lipsticks. You may need to ask your family what products they use on their skin. Do not include dry substances such as eye shadow and blusher as they are not moist enough to change the colour of the ph paper. Were you surprised at the range of hair and skin products in your house? Did you have enough room to record them all? Skin and hair products are used by people on a daily basis. Have you ever thought about how compatible these substances are with your skin? Do you think they could have the ability to damage your skin or lower your defence to infection? You are about to test the ph of skin and hair products in your home and evaluate their compatibility with skin ph. Aim To measure the ph values of a range of skin and hair products. Apparatus Approximately 20 cm of universal ph paper from your teacher. The ph colour scale from page 13 or the one supplied with ph paper Ten skin and/or hair products. Ten cotton buds or pop sticks (ice cream sticks). Part 4: What s growing on your skin? 17

151 Method 1 Collect ten or more skin and hair products from around the house. You listed these earlier. Record the product type and brand for each of the substances. 2 Being careful not to wet or contaminate the ph paper, roll it out on top of a sheet of paper or absorbent paper. The paper will protect the table surface. You may need to weigh down each end of the ph paper to keep it flat. If you have pieces of ph paper instead of a length of paper, place these on a clean A4 sheet of paper. You will need to keep track of what substance is being tested on what part of ph paper. Write the substance on the paper next to the ph paper. Refer to the diagram opposite. 3 Dip a cotton bud or a pop stick into the first substance to be tested. Remove any excess and dab the substance onto the place allocated on the ph paper. Be careful to apply only a small amount of the substance as the substance may spread, contaminating other sections. Use a different cotton bud or pop stick for each substance being tested. Some substances may need to be wetted first or lathered before sampling eg. soap. If so, be careful not to contaminate the ph paper with water drops or wet hands. 4 Repeat step three with the remaining substances. 5 When all substances have been applied, use your ph colour scale from page 13 to determine the ph of each substance. Record these in the results table. Some substances such as foundation may mask the ph colour. Try turning the ph paper over to observe the colour absorbed underneath. 18 Lifestyle chemistry

152 Gill Sans Bold Results Complete your results in the table below. An example is provided. Skin or hair product Brand ph colour ph soap sunlight yellow/mustard 6 Discussion Fill in the missing ph values and product names based on your results. a) The substances tested ranged from to in ph. b) was the most acidic substance with a ph of and was the most alkaline substance with a ph of. c) Generally the hair products tested range in ph from to. d) ph values of the skin products tested range from to. Turn to Exercise 4.2 at the back of this part to draw your conclusions on the ph values of a range of skin and hair products.? What progress have you made towards your open-ended investigation from Part 3? Your report must be submitted with Part 6 or by a date specified by your teacher. Part 4: What s growing on your skin? 19

153 Summary 1 Write three things you are unsure of about skin microflora _ 2 What do you need to do to gain an understanding about those points outlined in question 1? 3 Write three questions you would ask your teacher about the ph of skin if you were in class and did not fully understand the concept. 4 What do you need to do to gain an understanding about those points outlined in question 3? 5 a) What ph ranges do the skin and hair products have that you tested? b) How compatible are these ph ranges with skin ph? 20 Lifestyle chemistry

154 Gill Sans Bold Appendix 1 Microbes commonly detected on human skin Gram-positive cocci Staphylococcus aureus Staphylococcus auricularis Staphylococcus capitis Staphylococcus cohnii Staphylococcus epidermidis Staphylococcus haemolyticus Staphylococcus hominis Staphylococcus saccharolyticus Staphylococcus saprophyticus Staphylococcus simulans Staphylococcus warneri Staphylococcus xylosus Micrococcus luteus Micrococcus lylae Micrococcus nishinomiyaensis Gram-positive bacilli Corynebacterium jeikeium Corynebacterium urealyticum Corynebacterium minutissimum Propionibacterium acnes Propionibacterium avidum Propionibacterium granulosum Brevibacterium epidermidis Gram-negative bacilli Acinetobacter calcoacaticus Yeasts (Fungi) Malassexia furfur Moulds Trichopyton mentagrophytes Mite Demodex folliculorum Micrococcus kristinae Micrococcus sedentarius Micrococcus roseus Micrococcus varians Part 4: What s growing on your skin? 21

155 Appendix 2 Example answer to Exercise Include your used ph paper as shown above. 3 The skin and hair products tested ranged in ph from 5 to 7. Products within a ph range of 4 to 8 are compatible with skin as skin has a ph range of 4 to 8, however most skin has a ph of 5.5 to 6. The moisturisers, deodorants, soaps and hand creams tested are compatible with skin. Any substances used on skin with ph values below 4 and above 8 have the potential to change skin ph, thus altering the acid mantle. This could allow colonisation of the skin surface by harmful micro-organisms and result in skin irritation or infection. This answer is fictitious and does not indicate actual ph ranges of skin and hair products. 22 Lifestyle chemistry

156 Gill Sans Bold Suggested answers The microflora of skin 1 Microflora means micro-organisms surviving as microscopic communities. 2 Bacteria: single-celled procaryotic organisms belonging to the protist kingdom. Staphylococci: cocci bacteria appearing in grape-like formations. Cocci: sphere-shaped bacteria. Microbes: micro-organisms. Micro-organisms: microscopic, often single-celled, organisms. Sebum: oil produced by sebaceous glands in the dermis. Epidermis: outermost layer of the skin which protects the underlying tissue, forms a barrier from heat loss, water loss and micro-organisms. Keratin: tough protein present in the epidermis of vertebrate organisms. 3 Skin varies from dry areas to moist areas and wet areas, therefore conditions on the skin surface are not uniform. 4 Micro-organisms prefer moist environments. 5 Sweat from sweat glands contains sodium chloride and lactate. Sebum, an oily substance from sebaceous glands next to hair follicles, also provides nutrients that encourage micro-organisms. 6 The skin surface is constantly losing clumps of dead skin. Any microbes on the skin surface are lost. The ph of skin is slightly acidic at 5.5 ph. Most microbes prefer a ph neutral environment of 7. For these reasons, only specific microbes are able to survive on the skin surface. 7 The action of microflora on the skin causes the oil on the skin to become acidic. Microbial action on sebum releases smelly gases, commonly referred to as body odour. Part 4: What s growing on your skin? 23

157 8,9 Species of microflora Group Part of body found Staphylococcus epidermidis bacteria upper body and face Staphylococcus hominis bacteria legs and arms Micrococcus luteus bacteria head, legs and arms Corynebacterium jeikeium bacteria arm pit Propionibacterium acnes bacteria face and shoulders Propionibacterium avidum bacteria arm pit Propionibacterium granulosum bacteria side of nose Brevibacterium epidermidis bacteria in between toes Acinetobacter calcoaceticus bacteria groin and front of elbow Malassezia furfur fungus scalp, ear and back Trichophyton mentagrophytes fungus feet Demodex folliculorum mite face 10 a) Cocci look like small round spheres like ball bearings. Staphylococci resemble a bunch of grapes. (Other answers are acceptable.) b) Bacilli look like small rods. One bacillus resembles a chain with rods linked together. (Other answers are acceptable.) c) Moulds have threads joining each mould head containing spores. Bacteria are much smaller, needing a higher power microscope for viewing and are individuals or groups of spheres or rods. 11 Refer to the table above to locate areas particular species of microbes are found. 24 Lifestyle chemistry

158 Gill Sans Bold Acidity and alkalinity 1 0 strongly acidic increasing acidity 7 neutral ph Æ Ø 14 strongly alkaline 2 a) 4 is acid b) 6 is weakly acidic c) 13 is strong alkaline d) 10 is alkaline e) 7 is neutral f) 9 is weakly alkaline g) 1 is strongly acidic increasing alkalinity The ph scale Shade of ph paper ph Acidic/alkaline orange 4 acidic deep blue/green 10 alkaline deep orange 3 acidic light green 7 neutral maroon 1 strongly acidic yellow/mustard 6 weakly acidic Part 4: What s growing on your skin? 25

159 The ph of skin 1 The normal ph range of human skin is The normal ph range of human skin is acidic to weakly alkaline. 3 Sweat released from sweat glands is released at a ph of 5, causing the skin to have an acidic surface. 4 The underarms, forehead, between the toes and the soles of the feet have different ph values than the skin on the rest of the body. 5 The underarms, forehead, between the toes and the soles of the feet have slightly higher ph values, meaning they are more neutral than the rest of the body. 6 More microbes are associated with the underarms, forehead, toe webs and the soles of the feet than the rest of the body. 7 a) The high microbe populations metabolise sweat, sebum and keratin. Their wastes cause the higher ph levels. b) Sites such as the underarm are moist and separate to the rest of the body. For this reason, the ph is higher and more microbes are able to survive there as a result. 8 The acid mantle is the protective layer on the surface of the skin. 9 The acid mantle is thought to prevent more microbes from colonising the skin surface, as most microbes prefer a neutral ph. 10 Some scientists suggest that electrostatic forces between the skin surface and microbes determines skin microflora populations more than the acidity of skin. Skin and hair products 1 Imagine you are a microbe living on a person s face. You are comfortable living with a ph of 6. Suddenly, the person washes their face with a substance that has a ph of 8. The skin has changed from weakly acidic to weakly alkaline. You and your friends cannot survive above a ph of 7.5. You die, along with your friends. The skin surface is no longer acidic. The acid mantle has been altered. Different microbes are more able to colonise the area you were living on. They may cause disease on the skin surface. 2 What could happen to your skin if the ph was changed due to cleaning products? 3 Why is it important that products used on the skin be a similar ph to the skin surface? 4 What result could products used on the skin have if they have a ph lower than 5 or greater than 9? 26 Lifestyle chemistry

160 Gill Sans Bold Exercises - Part 4 Exercises 4.1 to 4.2 Name: Exercise 4.1 Choose two of these body parts: face arm underarm scalp back feet (and toes). For each of the two body parts you chose: state all the species of microflora present on the skin in that part of the body (if you chose the arm, you must include the species existing on the inside of the elbow) clearly draw an example of one of those species, indicating the species name (the species name must be scientifically written) explain the source of nutrients for the micro-organisms on that part of the skin explain the effects of microorganism activity eg. smell, acid environment. a) body part species of microflora present diagram and label of one microorganism present at this site. Part 4: What s growing on your skin? 27

161 source of nutrients effects of micro-organism activity b) body part _ species of microflora present diagram and label of one microorganism present at this site source of nutrients effects of micro-organism activity _? What progress have you made towards your open-ended investigation from Part 3? Your report must be submitted with Part 6 or by a date specified by your teacher. 28 Lifestyle chemistry

162 Gill Sans Bold Exercise 4.2 a) Attach your ph paper with this section complete with product names. Appendix 2 includes a graphic showing what your teacher expects. Put the ph next to the name of each substance tested or include a results table with this information. b) Comment on the accuracy of your ph readings of different substances used on the skin given that you made your own ph scale. c) Most skin has a slightly acidic ph of 5.5 or 6. You have tested the ph values for a range of skin and hair products. In the space provided: outline the range of ph values you observed discuss the compatibility of skin and hair products with regards to ph outline possible consequences of skin and hair products that are too acidic or too alkaline. You may refer to Appendix 2, which provides an example answer to this exercise. Part 4: What s growing on your skin? 29

163 Gill Sans Bold Senior Science HSC course Stage 6 Lifestyle chemistry Part 5: Dissolve it! IncorporatingOctober2002 AMENDMENTS

164 Senior Science Stage 6 HSC Course Lifestyle Chemistry Common substances Mixing it up Your skin What s growing on your skin? Dissolve it! Good medicine Medical Technology Bionics Information Systems Option

165 Gill Sans Bold Contents Introduction... 2 Solvents... 3 The universal solvent...4 Alcohol as a solvent...8 Solvent properties...11 Cosmetics and external medications Subdermal implants...14 The digestive system Summary Appendix Appendix Appendix Suggested answers Exercises Part Part 5: Dissolve it! 1

166 Introduction Have you ever wondered why some substances dissolve in water whilst others do not? In Part 5 you will be given opportunities to learn the chemistry behind the solubility of substances; the common substances that contain solvents; and how different types of tablets and medical implants regulate the released of medication over time. The nature of the digestive system is also outlined. In Part 5 you will be given opportunities to learn to: identify water and alcohol as commonly used solvents explain the relationship between the properties of solvents and their use in cosmetics and external medication identify cosmetics and external medications where water is the solvent identify cosmetics and external medications where alcohol is the solvent identify the parts of the digestive system outline the role of the stomach and the small intestine in breaking down food discuss the difference in ph of the stomach and the small intestine. In Part 5 you will be given opportunities to: identify data sources, gather, process, analyse and present information from secondary sources to identify how subdermal implants release their medication into the body. Extract from Senior Science Stage 6 Syllabus Board of Studies NSW, October The most up-to-date version is to be found at 2 Lifestyle Chemistry

167 Gill Sans Bold Solvents? What progress have you made towards your open-ended investigation from Part 3? Your report must be submitted with Part 6 or by a date specified by your teacher. 1 Do you remember the term solvent from Part 1? Write the definition for a solvent below. You may not realise that you rely on solvents every day. You wouldn t be able to make a cup of tea or a milkshake or toffee without a solvent. You wouldn t be able to wash your paintbrushes or take medicine without it. Soft drink wouldn t even exist without a solvent. 2 There are two common solvents. Use the clues below to identify the two solvents. a) This solvent can dissolve sugar and salt, is very common and quenches your thirst. Without this solvent, you wouldn t be able to make a cup of tea or swim in a pool. b) This solvent is found in nail polish remover and methylated spirits. It can cause people to act strangely and is regularly consumed at parties. It begins in a and ends in l. Check your answers. Part 5: Dissolve it! 3

168 H The universal solvent Have you ever wondered why water is capable of dissolving same substances and not others? The chemical concept is not as hard to understand as it seems. Water is the universal solvent. It has the ability to dissolve many substances. You should be familiar with the chemical formula for water, H 2 O. This means that each water molecules contains two hydrogen atoms and one oxygen atom. 1 On the diagram of a water molecule opposite, draw a + next to each hydrogen atom and a next to the oxygen atom. H O H Check your answer before moving on. 2 a) Draw an oval shape around the water molecule opposite. b) Outside the circle on the side with the oxygen molecule, write a symbol. This side of the molecule has a slightly negative charge. c) On the side with the hydrogen atoms, write a + symbol. This side of the water molecules has a slightly positive charge. Check your answer before moving on. H O You have just drawn a water molecule with polar ends. This means that certain ends of the molecule contains a positive or negative charge. Water molecules are polar. 4 Lifestyle Chemistry

169 Gill Sans Bold 3 Imagine a water molecule is like a magnet. One end is positive and the other end is negative. If you have five magnets, the positive end of each magnet will be attracted to the negative end of another. The water molecules below are attracted to each other like magnets. Some charges are displayed on the molecules. Write in the remaining charges. (Remember positive and negative charges are attracted to each other.) Check your answer before moving on. If water molecules did not have polar ends, water molecules would not stick together and life as we know it could not exist. The strong forces between water molecules are called cohesive forces. When another substance is added to water with stronger attractive forces than the water molecules themselves, the water molecules will be attracted to the new substance, thus dissolving it. This can be likened to a group of girls at a disco. Imagine a group of girls sticking together at a disco as water molecules. The forces holding them together are cohesive forces of positive and negative attraction. When a group of guys are added to the disco, the girls might be more attracted to them than each other. If you still imagine the girls as polar water molecules, they disperse, each becoming attracted to a boy. Sugar like water has OH groups. Parts of the molecule is polar. Therefore, sugar can dissolve in water. Non polar substances dissolve in other non-polar substances. polar substances dissolve in polar substances. Are you confused? If so, you are about to carry out an activity that should help. Part 5: Dissolve it! 5

170 4 Cut out the girl water molecules and boy sugar molecules from Appendix 1. The girls have their arms out representing the polar ends of a water molecule. One arm represents the positively charged end and the other represents the negatively charged end of a water molecule. The boys also have their arms out, representing the polar parts of sugar molecules. The positive ends of water molecules (girls) are attracted to the negative part of sugar molecules (boys) and vice versa. Two girls (molecules of water) are attracted to each end of a boy (sugar molecule). This causes each boy to be surrounded by a jacket of four girls. Remembering positive and negative charges attract, arrange the water and sugar molecules from Appendix 1 so that four water molecules (girls) are holding onto each sugar molecule (boy). Check your answer before moving on. 6 Lifestyle Chemistry

171 Gill Sans Bold By now, you should understand that: each water molecule contains two hydrogen atoms and one oxygen atom water molecules are polar with one end positively charged and the other end negatively charged. water molecules are attracted to each other with cohesive forces polar substances will dissolve in water the polar ends of a substance are attracted to the polar ends of water molecules, causing the substance to dissolve in the water. a substance that is not polar will not dissolve in water. If you do not understand the points outlined above, contact your teacher for help before moving on. Cordial, sugar in water, salt in water; tea and most disinfectants are examples of substances with water as a solvent. It is also used to dissolve acids and alkalis. Your swimming pool uses water as a solvent, salt and/or chlorine is dissolved in the water. Even though water is referred to as the universal solvent, it is not as easy to think of examples where water is used as a solvent only. You could probably think of many examples where water is used as a base for colloidal mixtures and suspensions. Water is used in soft drink as a solvent. 5 Identify four substances where water is used as a solvent. Check your answers.? What progress have you made towards your open-ended investigation from Part 3? Your report must be submitted with Part 6 or by a date specified by your teacher. Part 5: Dissolve it! 7

172 Alcohol as a solvent There are many different forms of alcohol. You may have heard of glycerol, ethanol, methanol and phenol. These are just a few forms of alcohol. The alcohol you are probably the most familiar with is in beer, wine and spirits. These all contain ethanol. Methylated spirits is mainly ethanol but is rendered undrinkable by the addition of methanol which is poisonous in small quantities. You have learnt about the polar nature of water and why it dissolves polar substances. The alcohols you will be investigating are mainly ethanol and methanol. These alcohols differ greatly from water as they are only slightly polar at one end and non-polar at the other end. This means that one end of the molecule possesses a charge and the other end of the molecule has no charge. List as many substances containing alcohol that you know of. For example, your list may contain alcoholic drinks or substances used on the skin. Ethanol and methanol Ethanol is a widely used solvent. Look at the structure of an ethanol molecule below. C represents carbon atom, H represents a hydrogen atom and OH represents oxygen and hydrogen combined as a hydroxide group. H H C H H C H OH The chemical structure of ethanol. The hydroxide (OH) end of an alcohol molecule is slightly polar, having a slight charge. The other end is not polar, having no charge. 8 Lifestyle Chemistry

173 Gill Sans Bold 1 Draw a molecule of ethanol below. On the hydroxide (OH) end of the molecule write slightly polar. On the other end of the molecule, write non-polar. 2 With one polar end and one non-polar end the alcohols, methanol and ethanol have interesting capabilities. Break the code below to determine these capabilities. a b c d e f g h i j k l m n o p q r s t u v w a b c d e f g h i j k l m n o p q r s t u v w the polar end can dissolve in water and the non-polar end can dissolve in oil Write your complete answer in the box below. Check your answers before moving on. Larger alcohol molecules Most of a larger alcohol molecule consists of a hydrocarbon chain made up of carbon and hydrogen atoms only. This means that larger molecules of alcohol such as cetyl alcohol are mostly non-polar. They can dissolve non-polar molecules. Because most of a larger alcohol molecule dissolves in oil and the rest dissolves in water, alcohol can be used as an emulsifier between oil and Part 5: Dissolve it! 9

174 water. This has many applications especially in the cosmetics industry. These are discussed later in this part. By now, you should understand that: ethanol and methanol have a slightly polar end and a non-polar end the polar ends of ethanol and methanol alcohols are able to dissolve in water the non-polar ends of ethanol and methanol alcohols are able to dissolve in oil in larger alcohol molecules the polar OH group is only a small part of the larger alcohol molecule polar substances can dissolve in small alcohol molecules like methanol and ethanol but not larger alcohol molecules like cetyl alcohol substances that are weakly polar or non-polar will dissolve in alcohols because most of any alcohol molecule is non-polar substances dissolving in alcohol are dispersed through the alcohol. If you do not understand the points outlined above, contact your teacher for help before moving on. Alcohols are used as solvents in textas, methylated spirits, stain removers, imitation vanilla essence, antifreeze, enamel paints, varnishes, mouth wash, cough mixtures, perfumes, after shave and nail polish remover. Identify four substances where alcohol is used as a solvent. Check your answer. Turn to Exercise 5.1 at the back of this part to identify different solvents. 10 Lifestyle Chemistry

175 Gill Sans Bold Solvent properties An interesting quality of the alcohols commonly used as solvents, methanol, ethanol and propanol, is that they evaporate quickly. If an alcohol is used on the skin surface, it feels cool and soothing. This is because it removes body heat as it evaporates, leaving the skin with a cool sensation. In high enough quantities, alcohol also has the ability to dehydrate the cells of microbes, causing them to die. Antiseptics and disinfectants rely on this property of alcohol to kill bacteria. You have also already learnt that some alcohols can be used as surfactants and emulsifiers as some have a polar and a non-polar end. 1 Use the points below to record three properties of alcohol from the passage above. Water has the ability to dissolve polar substances. You may only be aware of table salt, however, there are many other salts that dissolve in water. Acids, alkalis and the alcohols, methanol and ethanol, dissolve in water. Water evaporates, however not as fast as alcohol, therefore the cooling effect is not as noticeable. Water also is capable of hydrating cells. 2 Record three properties of water from the passage above. Check your answers. The properties of solvents often determine their use. Some substances you commonly use contain these solvents. Part 5: Dissolve it! 11

176 Cosmetics and external medications Almost all cosmetics and external medications such as creams, sprays and ointments contain one or more solvents. 1 Record any cosmetic products or medications you have used on your skin over the last two weeks. This includes: deodorants, moisturisers, shaving cream, perfume, soap, after shave, ointment, rash or bite treatments, burn treatments, heat rubs, disinfectants, nail polish, nail polish remover and any others you can think of. If you do not use many of these substances, you may question another person. You may have found that you use more substances than you thought. In most cases, the substance would not exist without a solvent. Water may also be referred to as aqua in an ingredients list. Alcohol can have many names. The term alcohol or alcohol based in a list of cosmetic ingredients usually refers to ethanol. The following list of names describe other forms of alcohol used: cetyl alcohol stearyl alcohol cetearyl alcohol (also called cetostearyl alcohol) denatured alcohol lanolin alcohol SD alcohol-a; SD alcohol 40 methanol/methyl alcohol. This list of alcohols does not totally cover the alcohols you are likely to find in cosmetics and medications, however it is a guide. 12 Lifestyle Chemistry

177 Gill Sans Bold Some substances contain water and alcohol. You already know the properties of water and alcohol. The water is often used as a skin hydrator as well as a solvent for acids, alkalis, salts and other polar substances. In most cases, alcohol is present to dissolve non-polar substances such as oils. Once the alcohol has dissolved these substances, the alcohol may be dissolved in the water. You may find it strange that oils should be present in cosmetics such as moisturisers, however they play an important role. Oils not only replace natural oils stripped by washing with soap and cleansers, they coat the skin surface, minimising the evaporation of water from the skin. In other instances, alcohol may be present in such things as cleansers, and toners. Their function here uses the non-polar property to dissolve away non-polar skin oils. However, skin cosmetics should not contain greater then the recommended 50% - 60% alcohol as it draws moisture out of the skin, having a drying effect. Water is also often present in the substances to help lathering and removal of oils and grime. The non-polar nature of alcohol also dissolves non-polar molecules with odours used in perfumes and after shaves. Once applied to the skin, the alcohol evaporates, leaving a fragrant oil emitting an odour. This is left on the skin, dissolved in non-ionic skin oils. These odours are quickly destroyed through abrasion or excess heat. Disinfectants and some cosmetics rely on relatively high concentrations of alcohol to draw moisture out of skin micro-organisms, killing them and reducing the risk of infection. Are you ready to investigate the cosmetics and skin medications in your home? If you don t have many cosmetic products and external medications in your home, can you visit a supermarket, friend or neighbour? Turn to Exercise 5.2 at the back of this part to investigate solvents used in cosmetics and external medications? What progress have you made towards your open-ended investigation from Part 3? Your report must be submitted with Part 6 or by a date specified by your teacher. Part 5: Dissolve it! 13

178 Subdermal implants Some medications can be placed under the skin surface. The medication is released over a period of time. Turn to Appendix 2 on Controlled release drug delivery. Read the entire appendix then carry out the following activity. 1 The following diagrams demonstrate what is described in Appendix 2. Use the information in Appendix 2 to explain what is occurring in each diagram below. Stage 1 Diagram of subdermal implant inner core with hydrophobic film Explanation outer core with hydrophilic film Lifestyle Chemistry

179 Gill Sans Bold 2 What substance dissolves the outer film, causing medication in the outer core to be released? 3 Water alone will nor cause the inner film to degrade. What must be in contact with the inner membrane to cause it to weaken, enabling it to burst? 4 Explain the function of subdermal implants currently used in humans. Check your answers. The solubility of medication taken orally determines the absorption of drugs. The nature of the digestive system determines the solubility and absorption of drugs. Turn to Exercise 5.3 at the back of this part to explain how body ph influences the solubility of medication in subdermal implants.? What progress have you made towards your open-ended investigation from Part 3? Your report must be submitted with Part 6 or by a date specified by your teacher. Part 5: Dissolve it! 15

180 The digestive system Are you able to identify parts of the digestive system? Can you recall the roles of the stomach and small intestine in the digestion of food? This section gives you opportunities to refresh your memory or learn about the digestive system through fun activities. Listen to the Digestive system section of the Skin audiotape/internet audio files to guide you through the following activities. 1 Label the parts of the human digestive system using the labels in Appendix 3. The human digestive system. Check your answers before moving on. 16 Lifestyle Chemistry

181 Gill Sans Bold 2 State the three food types. 3 Use the Digestive system information in the Skin audiotape/internet audio files to complete the table below. Organ Role in digestion stomach duodenum gall bladder pancreas small intestine Part 5: Dissolve it! 17

182 4 Explain why the stomach and the small intestine have different ph values. _ 5 In general terms, explain the role of the stomach in breaking down food. _ 6 In general terms, explain the role of the small intestine in breaking down food. _ Check your answers. The substances you consume must become soluble through digestion to be absorbed by the body and used for energy. How soluble a substance is determines the rate at which it is absorbed by the body. Turn to Exercise 5.4 at the back of this part to label and state the functions of parts of the human digestive system.? What progress have you made towards your open-ended investigation from Part 3? Your report must be submitted with Part 6 or by a date specified by your teacher. 18 Lifestyle Chemistry

183 Gill Sans Bold Summary Below is a list of the contents for Part 5. Write three things you learnt underneath each heading title. Keep your answers brief as they are they are to represent key concepts only. The universal solvent Alcohol as a solvent Solvent properties Cosmetics and external medications Part 5: Dissolve it! 19

184 Subdermal implants The digestive system? What progress have you made towards your open-ended investigation from Part 3? Your report must be submitted with Part 6 or by a date specified by your teacher. Record five things you need to do in the next week for your open-ended investigation. 20 Lifestyle Chemistry

185 Gill Sans Bold Appendix 1 water water sugar water water sugar water water sugar water water sugar Part 5: Dissolve it! 21

186 22 Lifestyle Chemistry

187 Gill Sans Bold Appendix 2 Controlled release drug delivery Subdermal implants in animals An implant placed under the skin surface contains a compressed core and two layers of film coating. The outer film is compatible with skin tissue and degrades at a set rate when in contact with water from the body. The dissolution of the outer membrane releases medication between the first and second layers of film. The inner core, protected by the hydrophobic film begins to swell as the outer film degrades. The inner film is hydrophobic but dissolves at body ph. Non-polar molecules inside the film become polar when in contact with body ph. The polar molecules are then more able to dissolve in body water. The swelling of the inner core, combined with the dissolving of the inner film causes the inner film to rupture twenty one to sixty days after implantation. In this way, the core medication is released in a pulse. The medication is then able to travel through the bloodstream to target cells. The overall effect is similar to two injections of a drug with only one veterinarian bill. The above information has been adapted from: Theil, W J. Panagiotidis, J. Controlled Release Drug Delivery, < (accessed 17 June 2000) Subdermal implants in humans Subdermal implants are currently being used to deliver steady doses of hormones in females, replacing the contraceptive pill. Such implants are effective for up to five years. Part 5: Dissolve it! 23

188 The slow release of drugs work on similar principles to those outlined above, however the chemistry behind the slow release of drugs is more complicated. 24 Lifestyle Chemistry

189 Gill Sans Bold Appendix 3 Cut out the following labels for the human digestive system. small intestine stomach liver oesophagus large intestine duodenum gall bladder rectum pancreas mouth Part 5: Dissolve it! 25

190 26 Lifestyle Chemistry

191 H H Gill Sans Bold Suggested answers Solvents 1 Solvents are substances that will dissolve a solute. 2 a) water b) alcohol The universal solvent 1 H O 2 H O 3 4 sugar sugar sugar sugar Part 5: Dissolve it! 27

192 5 Water is a solvent in cordial, tea with sugar, disinfectants and swimming pools. (Other answers are acceptable.) Alcohol as a solvent 1 non-polar H H C H H C H OH slightly polar 2 The polar end can dissolve in water and the non-polar end can dissolve in oil. Larger alcohol molecules Alcohol is used as a solvent in methylated spirits, enamel paints, after shave and perfumes. (Other answers are acceptable.) Solvent properties 1 Alcohol evaporates quickly, having a cooling effect. Alcohol is able to dehydrate living cells, killing them. Some alcohols may be used as surfactants or emulsifiers due to the polar and non-polar ends of the molecules. 2 Water is able to dissolve polar substances due to the polar nature of water molecules. This includes acids, alkalis and some alcohols. Water is able to hydrate cells Water evaporates causing a mild cooling effect. Subdermal implants 1 Stage Explanation 1 The subdermal implant contains an inner core and outer core. The inner core is protected by a hydrophobic film and the outer core is surrounded by a hydrophilic film 2 The outer film dissolves in body water, releasing medication to the body. The inner core remains protected by the hydrophobic film. 3 As the outer core degrades, water moves into the inner core, causing it to swell. 4 The inner core eventually ruptures, releasing a pulse of medication to the body 21 to 60 days after initial implantation. 28 Lifestyle Chemistry

193 Gill Sans Bold 2 Water dissolves the outer film, causing medication in the outer core to be released into the body. 3 The inner core must be in contact with body ph for it to degrade, allowing it to weaken and burst. 4 Subdermal implants are currently used in humans replacing the contraceptive pill. The implants can protect females against pregnancy for up to five years. The digestive system 1 mouth oesophagus liver gall bladder stomach duodenum pancreas small intestine large intestine rectum 2 The three food types are carbohydrates, protein and fats. 3 Organ Role in digestion stomach duodenum gall bladder begins digestion of protein and churns food into a paste; protease enzymes digest protein; the protein is broken down into peptides; hydrochloric acid helps the enzymes present to function and kills microbes. receives contents of stomach, bile from the gall bladder and enzymes from the pancreas; the digestion of fat which has been broken up into smaller globules commences; acidic stomach contents are neutralized so that ph rises to between 6 and 8 secretes bile into the duodenum; bile breaks oil globules into smaller globules; bile also neutralises stomach acids, causing the food to become more alkaline Part 5: Dissolve it! 29

194 pancreas enzymes further break down protein, carbohydrate and starch which are more able to function in the higher ph conditions small intestine the small intestine produces a fluid containing enzymes to complete digestion of carbohydrates, protein and fats; peptidase enzymes break down proteins; lipase enzymes further digest fat; lactase breaks down milk sugar (lactose) and other enzymes break down other carbohydrates carbohydrates have become glucose; proteins have become amino acids and fats have become fatty acids and glycerol; these are absorbed across the small intestine wall into the bloodstream 4 The stomach and the small intestine have different ph values as different enzymes function best in differing levels of acidity and alkalinity eg. pepsin functions best in the stomach at a ph of 1 to 2 while other enzymes such as protease and lipase function best in a ph range of 6 to 8. 5 The stomach churns food into a paste and begins to break down proteins into peptides with protease enzymes. 6 The small intestine contains a mixture of enzymes from the gall bladder, pancreas and small intestine. Bile breaks down fats into small globules. Pancreatic juices and juices secreted from small intestine walls digest proteins, carbohydrates and fats with enzymes. Once soluble, the digested food may be absorbed into the bloodstream. 30 Lifestyle Chemistry

195 Gill Sans Bold Exercises - Part 5 Exercises 5.1 to 5.4 Name: Exercise 5.1 The diagram below shows a shaded polar substance (solute) dissolved in another polar substance (solvent). 1 Is the unshaded solvent in the above diagram water or alcohol? Explain your answer. Part 5: Dissolve it! 31

196 2 The diagram below shows water, oil and alcohol molecules. a) Identify the water, oil and alcohol molecules in the legend below. b) Outline your reasons for molecule identification in the legend. Legend molecule water/alcohol/oil reason c) Explain what is happening in the above diagram using the words: polar, non-polar, solvent; emulsion; alcohol; water; and oil. You may use more than one sentence. 32 Lifestyle Chemistry

197 Gill Sans Bold Exercise 5.2 Collect six cosmetics and/or external medications from the following list: deodorants ointment moisturisers rash or bite treatments shaving cream burn treatments perfume heat rubs after shave disinfectants nail polish vapour rubs nail polish remover disinfectants. Only choose products with ingredients listed on them. Some substances may list the active ingredient only and are not recommended for your investigation unless the active ingredient is a form of alcohol. Choose at least one product that contains no alcohol. Look at the list of ingredients on the package. Place a tick in the relevant box to indicate the solvents present. If alcohol is present, place a tick in the alcohol column. Remember, there are many names for alcohol listed on page 12. Other alcohols may be present other then those indicated earlier. If water (aqua) is present, place a tick in the water column. The first one has been done for you as a guide. Substance External medication Cosmetic Alcohol present Water present Lux awaken moisturiser Part 5: Dissolve it! 33

198 1 a) List the cosmetics and medications containing water only. b) Place a small amount of one of those substances on your skin. Describe how it feels eg. cold, warm, oily, slimy. 2 a) List the cosmetics and medications containing alcohol only. b) Place a small amount of one of those substances on your skin. Describe how it feels. c) Use the information on the properties of alcohol on page 11 to explain why the substance containing alcohol feels like it does. 3 a) List the cosmetics and medications containing alcohol and water. b) Use the information on page 10 to explain why these substances contain alcohol and water. 34 Lifestyle Chemistry

199 Gill Sans Bold Exercise 5.3 Explain how subdermal implants rely on body ph to deliver medication to body tissue. You may use diagrams in the space provided below to help with your explanation.? What progress have you made towards your open-ended investigation from Part 3? Your report must be submitted with Part 6 or by a date specified by your teacher. Part 5: Dissolve it! 35

200 Exercise Label the parts of the digestive system identified with a line on the diagram below. 2 Fill out the functions in digestion of those parts indicated with a box. Include as much detail as possible. Show variations in ph. 36 Lifestyle Chemistry