Name: Date: Block: Introduction: BIO 611 Polarity and Mixing Lab When you mix two substances together, the first thing they do is decide whether or not they like each other. If they do, one will usually dissolve in the other. If they don t, they will likely remain separate. This observation is usually summed up with the statement Like dissolves like. For example: Two polar substances will dissolve or mix together. Two nonpolar substances will dissolve or mix together. One polar substance and one nonpolar substance will NOT dissolve or mix together. If two substances mix together, we call them soluble (one can dissolve in the other). If two substances do not mix together we call them insoluble. In this activity, we will deal with the following substances and mixtures: 1. Water (H 2 O) 2. Sucrose or table sugar (C 12 H 22 O 11 ) 3. Vegetable oil (a mixture of lots of big molecules that are long chains of carbon and hydrogen) 4. Milk (a mixture of water, fats, and proteins that has been homogenized forced to mix well with each other, whether they like it or not) 5. Food coloring (dye that is dissolved in water or alcohol) 6. Dish soap - a mixture of molecules containing long chains of carbon and hydrogen. One end is polar; the other end is nonpolar. (Pictured below.) 1
Part I - Procedure: Please make all observations as detailed as possible on your Analysis Sheet. Note that you should write down what you see (e.g. The crystals slowly disappeared. ) rather than your conclusion about what is happening (e.g. It dissolved. ) Sucrose and Water: 1. Fill a cup about 1/3 full with water. 2. Add a small amount of sugar. 3. Observe for a minute. 4. Stir. Observe for another minute. 5. Rinse out the cup thoroughly. Oil and Water: 1. Fill a cup about 1/3 full with water. 2. Add 3-5 drops of oil. 3. Observe for a minute. 4. Stir. Observe for another minute. 5. Rinse out the cup thoroughly. Sucrose and Oil: 1. Fill a small cup about 1/3 full with oil. 2. Add a small amount of sugar. 3. Observe for a minute. 4. Stir. Observe for another minute. 5. You may throw out the cup of oil and sugar when finished. Food Coloring, Water and Soap: 1. Get a Petri dish and fill the base 1/3 full with water. 2. Add a drop of food coloring to the water and record your observations. Do NOT mix. 3. Next, Add a drop of dish soap to this mix and record your observations. 4. Empty Petri dish and rinse very well to remove all soap. 2
PART I ANALYSIS SHEET: Polarity & Mixing Lab Data Table: Part I Experiment# SubstancesMixed Observations drawapictureandwriteadescription Together 1 WaterandSugar 2 WaterandOil 3 OilandSugar 4 WaterandFoodColoring Water,FoodColoring, andsoap 3
PartI:Analysis Basedonyourobservations,determineifthefollowingmoleculesarepolarornonpolarand explain. Substance CircleOne: Why? PolarorNonpolar water PolarorNonpolar sugar PolarorNonpolar oil PolarorNonpolar food coloring PolarorNonpolar soap PolarorNonpolar A. Couldyouhavepredictedwhethersucroseispolarornonpolarbasedsolelyonits chemicalformula,whichisc12h22o11? Whyorwhynot? B. Canyouexplainsoap sbehaviorbasedonitsmolecularstructure(drawnonthefront page)? Whyorwhynot? 4
PartII Procedure: 1. Fill a clean Petri dish base 1/3 full with milk. 2. Add three drops of food coloring in a triangle (See Figure 1) - Keep the drops far apart - Do NOT mix! - You may use different colors. 3. WAIT for ONE minute. 4. In the circle provided, draw what you see after one minute. Next to the picture, write your observations. DRAWING OBSERVATIONS 5. How do your results compare to the behavior of food coloring in water? 6. Add 1 drop of dish soap to the MIDDLE of the triangle. (See Figure 2) - Do NOT mix! 7. During the FIRST minute, write down ALL of your observations. After a minute, draw what you see. S DRAWING OBSERVATIONS Figure2 5
8. Clean up. Rinse and wash out your Petri dish with some soap. Part II Analysis 1. As noted in your chart, soap is both polar and nonpolar. (see soap's molecular structure below). In the blanks provided, label which part of milk (cream and water) will be attracted to the POLAR part of soap and which will be attracted to the NONPOLAR part of soap. 2. Using the pre-lab, your answer to Question 1, and what you know about polar and nonpolar molecules, explain your observations for Step 7 when soap was added to the dish of milk and food coloring. You may draw a picture to help explain what is going on. 3. Howdoesasoapmolecule sstructurehelpitgetgreaseanddirtoffaperson shands? 6
PartIII:MarblingwithShavingCream Shaving cream is soap. Remembering what you learned about a soap molecule from Part I of this lab,trytocorrectlypredictwhatwillhappeninthissimpleartactivityusingshavingcream,water, andfoodcoloring. 1. IndividualPrediction:Doyouthinkthatadropoffoodcoloringcanmixanddissolveeasily intoapileofshavingcream?whyorwhynot? 2. Procedure: Step 1: Squirt a pile of shaving cream roughly the size of your fist onto the paper plate. Smoothoutthetopoftheshavingcreamwithacraftstick. Step 2: Apply a drop or two of several different food colors to various locations on the shavingcream.observehowthecolorspreads. Step3:Dragatoothpickthroughthecoloreddropsontheshavingcreamtocreatepatterns withthecolor. Step 4: Press a piece of paper onto the surface of the shaving cream. Lift the paper and scrapeofftheshavingcreamthatisstucktoitusingthecraftstick.returntheexcess shavingcreamtotheoriginalpile. Step 5: Now let us do another cool marbling trick. Using the craft stick, mix the pile of coloredshavingcreamuntilitisoneuniformcolor.ifthecolorisverypale,mixina fewmoredropsoffoodcoloring. Step6:Applyasingledropofwatertothesurfaceofthecoloredshavingcreamandobserve what happens. Try this again at several different places on the surface. Now repeat step4usinganotherpieceofpaper. 3. PresentingyourData:Allowyourmarbledpaperstodryonthecounter.Putyournameand classblockinthebottomright handcornerofthepaperssothatyourartworkcanbereturned toyou. 4. TheResults: A. Evidence:Whatdidyouobservehappenwhenyouplacedadropoffoodcoloringonapile ofshavingcream? B. Evidence:Whatdidyouobservehappenwhenyouplacedadropofwateronapileof coloredshavingcream? 7
5. ClassDiscussion:Usingyouknowledgeaboutpolarity A.Whydoyouthinkthedropoffoodcoloringbehavedthewayitdidintheshavingcream? B.Whydoyouthinkthedropofwaterbehavedthewayitdidintheshavingcream? 6. Think about this: A phospholipid molecule is an integral part of every cell s membrane. A phospholipidisstructurallysimilartoasoapmolecule halfthemoleculeispolarandtheother half is nonpolar. All cells live in a fluid environment and, likewise, are filled with fluid. Take a typicalredbloodcellforexample.aredbloodcelltravelsinthebody sblood,whichismostly water.insidetheredbloodcellthereisafluidcalledcytoplasm,whichisalsomostlywater. A. Howdoyouthinkphospholipidsarrangethemselvesinordertomakeamembrane (boundary)ofacell? B. Drawapictureofacellmembranecomposedofphospholipidsbelow.Labelyour diagram. 8