Teacher's/Lecturer's Sheet Alkalis - constituents of household detergents (Item No.: P7158700) Curricular Relevance Area of Expertise: Chemie Education Level: Klasse 7-10 Topic: Anorganische Chemie Subtopic: Säuren und Basen, Protonenübergänge Experiment: Laugen - Bestandteil von Haushaltsreinigern Difficulty Preparation Time Execution Time Recommended Group Size Easy 10 Minutes 10 Minutes 2 Students Additional Requirements: Experiment Variations: Keywords: alkalis, material property, houshold detergents Task and equipment Information for teachers Learning objectives Alkalis are contained in many household detergents. They are used there because of their decomposing and thus cleaning effect with regard to organic contaminants. In addition to that they are germicidal. Notes on set-up and procedure Preparations Have some household detergent ready. All commercially available household detergents containing ammonia can be used. Remarks on the students' experiments Make sure that when the household detergent is heated, this process is stopped immediately when the first traces of ammonia can be smelled. The test tube must be shaken slightly during heating since otherwise boiling would be delayed. Add some boiling stones, if necessary. Hazard and Precautionary statements
Teacher's/Lecturer's Sheet Sodium hydroxide: H314: Causes severe skin burns and eye damage. H290: May be corrosive to metals. P280: Wear protective gloves/protective clothing/eye protection/face protection. P301 + P330 + P331: P309 + P310: P305 + P351 + P338: Phenolphthalein: IF SWALLOWED: rinse mouth. Do NOT induce vomiting. IF exposed or if you feel unwell: Immediately call a POISON CENTER or doctor/physician. IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing. H226: Flammable liquid and vapour. P210: Keep away from heat/sparks/open flames/hot surfaces. - No smoking. P233: Keep container tightly closed. Hazards Sodium hydroxide is highly corrosive. Do not touch it with bare fingers! Put on protective glasses! When the household detergent is heated, harmful and evil smelling gases are released. The experiment must thus be carried out under the fume hood! Remarks on the method This experiment goes back to the changes of indicator colours already treated in conjunction with the subjects of "acids". If they haven't been taught yet, the experiments given there on the preparation of indicators and theis reactions can be slightly modified and used in this context here, too. Waste disposal Put all the solutions into the collecting tank for acids and alkalis.
Alkalis - constituents of household detergents (Item No.: P7158700) Task and equipment Task Alkalis are contained in what substances and what is their purpose? Examine household detergents for their components.
Equipment Position No. Material Order No. Quantity 1 Protecting glasses, clear glass 39316-00 1 2 Beaker, 100 ml, low form, stackable, plastic 36081-00 1 3 Test tube holder, up to d 22mm 38823-00 1 4 Test tube, 18x188 mm, 10 pcs 37658-03 0.2 5 Test tube rack for 12 tubes, holes d= 22 mm, wood 37686-10 1 6 Spatula, powder, steel, l=150mm 47560-00 1 7 Pipette with rubber bulb 64701-00 1 8 Litmus paper, red, 1 box 30678-02 1 9 Wash bottle, 250 ml, plastic 33930-00 1 Additional material Butane burner f.cartridge 270+470 47536-00 1 Butane catridge CV 300 Plus, 240 g 47538-01 1 Sodium hydroxide, flakes, 500 g 30157-50 1 Water, distilled 5 l 31246-81 1 Phenolphthalein, 0,5% soution in ethanol, 100 ml 31715-10 1 Household detergent
Set-up and procedure Set-up HaIards Sodium hydroxide is highly corrosive. Do not touch it with bare fingers! Put on protective glasses and rubber gloves! When the household detergent is heated, harmful and evil smelling gases are released. The experiment must thus be carried out under the fume hood! Set-up Fill the two test tubes one quarter full with household detergent and put them into the test tube rack (Fig. 1). Fig. 1 Fill the glass beaker with distilled water (filling height approximately 1 cm) and add some drops of phenolphthalein solution (Fig. 2). Fig. 2 Procedure Pour the household detergent from one of the test tubes into the distilled water with the added phenolphthalein solution (Fig. 3).
Fig. 3 Use the spatula to put two sodium hydroxide pellets into the second test tube (Fig. 4). Heat the household detergent with the added sodium hydroxide very carefully (Fig. 5). Carry out smelling tests as short intervals. Fig. 4 Fig. 5 Stop heating when the first traces of evil smelling gases can be detected. Hold a piece of humidified red litmus paper over the test tube orifice (Fig. 6). Fig. 6 Waste disposal Put the content of all vessels into the collecting tank for acids and alkalis.
Report: Alkalis - constituents of household detergents Result - Observations (10 Punkte) Write down your observations. Result - Table 1 (4 Punkte) Enter the changes of the indicator colours into Table 1. Indicator colour Phenolphthalein in distilled water 1 Phenolphthalein after the addition of the detergent 1 Litmus paper before the heating of the detergent 1 Litmus paper after the heating of the detergent 1
Evaluation - Question 1 (10 Punkte) Draw the conclusions from your observations. Evaluation - Question 2 (10 Punkte) Explain why household detergents contain the determind components.
Evaluation - Question 3 (9 Punkte) State some other indicators that could be used and the change of colour they would show in this experiment. Indicator Colour before Colour after the addition of the household detergent 1 1 1 1 1 1 1 1 1