Everyday Life and Chemistry

Abstract

David Waddingon [1] caricatured chemical education from his point of view. Students of classes 9–11 of a German secondary high school also expressed similar views with their comments: “Chemistry class does not seem to be so senseless if you can use the content in everyday life; there should be more references to practice then chemistry class would not be an abstract complex of formulae; in particular references to everyday life are good for the back-ground and they benefit those who won’t choose a profession in the chemical industry” [2].

Appendices

Problems and Exercises

• P8.1 Many phenomena of everyday life or nature can be “translated” into chemistry or chemical reactions. Give five examples for those phenomena and their scientific interpretation. Look for useful experiments according to these examples and write chemical equations.

• P8.2 In some cases, chemicals of your kitchen or bathroom can replace the chemicals of the laboratory. Give five examples and explain the experiments or reactions. Describe topics or contexts of chemical education where the use of those chemicals may be helpful.

• P8.3 For students’ motivation, everyday life phenomena should be put at the beginning of a topic in chemistry class. Give five examples, describe the experiments, and their interpretation. How do the lessons continue after successful motivation?

• P8.4 The attitudes of students concerning chemistry or chemical education are often negative (“chemistry is bad for our health,” “in chemistry classes we have mostly formulae we cannot understand”). What steps or actions could be helpful to turn those attitudes around?

• P8.5 There are some days free of classes and you have to plan a chemistry project. What topic, what context you like to choose for those days? What tasks or problems should the students solve in these days? Which questionnaire would you develop to ask about the interests of your students? In which way would you respect different wishes of boys and girls?

Experiments

In Chap. 8.2, many reactions of different household chemicals are described already so that the “problem” and even the “explanation” are given with those interpretations. Therefore, the paragraph “problem” will not be shown in the following short instructions – only the “procedure” is given. Because the “material” consists mostly of some test tubes, this paragraph is also removed.

• E8.1 Tab Cleaner “NaOH Type” Put a spoon of the cleaning powder on a watch glass and observe white salt crystals and silver-colored metal splinters. A part of the substance is mixed with a small amount of water in a test tube: an exothermic reaction begins and a smell of ammonia is noticeable. Pieces of wool fabric are added: they decompose slowly.

  In a second experiment, pure sodium hydroxide is mixed with aluminum shavings and little water, the produced gas is collected in a second test tube. After igniting the gas, a little bang is observed: the produced gas is hydrogen.

• E8.2 Toilet Cleaner “HSO ⁻₄ Type” A small amount of substance is given in a test tube, white salt is observed. It is dissolved in water, the solution is examined with universal indicator paper: acidic reaction. A small amount of calcium carbonate is added to the solution: the sample will be dissolving with gas development. A burning wooden splint is extinguished: the gas is carbon dioxide.

• E8.3 Sanitary Cleaner “ClO⁻ Type” Cleaner liquid is given into a test tube, a strip of indicator paper is dropped, some drops of methyl blue solution are added: indicator paper turns white, blue solution turns colorless.

  A second sample is mixed in a test tube with toilet cleaner (E8.2): the smell and color of the developing gas indicate chlorine (dilute the solution in the vent to stop the reaction).

• E8.4 Deodorant “Al³⁺ Type” One brand of deodorant is Hydrofugal spray. Indicator paper is moistened: acidic reaction. Little aluminum chloride hexahydrate is dissolved in water (test tube) and examined with indicator paper: acidic reaction.

• E8.5 Mineral Tablets “Ca²⁺ and Mg²⁺ Types” One tablet is given into a glass of water: gas bubbles, formation of carbon dioxide. The reaction is repeated with a mixture of calcium carbonate and citric acid, water is added.

  In a gas developer, water is dripped on a tablet, the developed gas is collected in a syringe. As soon as the 100 mL mark is reached, the gas is moved out and new developed gas is collected again. The quantity of gas is determined; the gas is examined with a burning splint.

  The reaction of one tablet is performed in a pneumatic tub, in such a way that the gas is collected in a water filled cylinder. The volume will be marked. A second tablet will be dissolved in the same way: the observed volume of the gas portion is much larger than previously with the first tablet (compare with E2.3).

• E8.6 Table Salt “Iodine Type” Ingredients of the salt will be checked on the label of the container. Iodinated table salt will be mixed with potassium iodide solution and acidified with sulfur acid solution: brown-colored iodine solution appears. If you add starch solution, the specific blue-colored solution shows free iodine, as well. The experiment will be repeated with pure sodium iodate.

• E8.7 Baking Powder “Sodium Bicarbonate Type” The baking powder will be floated with a small amount of water and heated: gas development. It will be heated strongly in a dry test tube; the gas that forms will be collected in a syringe and examined with a burning splint: carbon dioxide.

• E8.8 Baking Powder “Ammonium Carbonate Type” The experiments of E8.7 will be repeated with this baking powder and pure ammonium carbonate. The mixture of gases formed will be examined with wet indicator paper: alkaline reaction. The smell also indicates ammonia.

• E8.9 Textile Decolorizer “Sodium Dithionite Type” Ingredients are checked on the label of the container. In a test tube, a sample of a methyl blue solution will be mixed with a small amount of textile decolorizer powder; in a second test tube with pure sodium dithionite: reaction of the blue solution until decolorization.

• E8.10 Developer “Hydrochinone Type” Silver chloride will be precipitated in two test tubes: keep one test tube in the cupboard without light for ten minutes, the other in bright light. The last precipitate turns much darker compared with the first one. Alkaline hydroquinone solution (Xn) is added to both test tubes: both precipitates turn black.

  In the photolab under red light, a key ring or something like that is placed on photographic paper and then exposed for a short time. The photographic paper is then put into an already prepared developer solution: the black-and-white picture develops in one minute. The photo has to be rinsed with diluted acetic acid to stop further developing of the photo. The photo is then fixed in special fixer solution before it can be viewed in white light (compare with E8.11).

• E8.11 Fixer “Sodium Thiosulfate Type” Silver chloride will be freshly precipitated in a test tube, and the resulting suspension will be diluted. Concentrated sodium thiosulfate solution is given into the dilute suspension and then shaken: the white precipitate of silver chloride dissolves into a clear solution.

  In the photolab, the developed photo (E8.10) is dropped into the fixer solution and left there for a while. After that, another newly developed photo and the fixed photo are brought into normal white light: the fixed photo stays unchanged, while the entire nonfixed photo turns totally black.

• E8.12 Etching Chemical “Fe²⁺ Type” Iron(III) chloride solution (Xn) is prepared in a big test tube. On a copper-coated synthetic strip, a short name is written on it using a wax pen. This strip is dropped into the prepared solution: after a few minutes, only the written name can be seen, the remaining copper is dissolved.

• E8.13 Accumulator “Pb/PbO₂ Type” A car battery is demonstrated; first the voltage of one cell is measured (2 V) and then the voltage of all six cells together (12 V).

  A beaker is filled to three quarters with sulfuric acid solution (20%, C), two lead strips are arranged and fixed in such a way that they do not contact each other. The lead strips are connected to a transformer by two cables, a direct current voltage has to adjust in this way so that a gas development can be seen: on one lead strip a layer of a red–brown substance is generated (PbO₂), the other lead strip stays as before (Pb). The transformer is removed after a few minutes; the voltage between the two strips is measured: about 2 V. An electric motor is connected, which runs for a while and then stops (compare with E4.10).

• E8.14 Flashing Cement “Ca(OH)₂ Type” Ingredients are checked on the label of the container. The mixture of the substance with little water is tested with indicator paper: alkaline reaction.

  In a beaker, little water is given to fresh calcium oxide (Xi): increase of the volume under hissing noises; strong exothermic reaction. The white product is inspected with a wet strip of indicator paper: strong alkaline reaction.

  The product (or calcium hydroxide (Xi) out of a supply bottle) is mixed with water in an Erlenmeyer flask, carbon dioxide is added from a steel bottle and a syringe filled with carbon dioxide is connected to the flask. The flask is moved so that the mixture spreads inside the flask: the piston of the syringe moves; the mixture heats up.

• E8.15 Fire Extinguisher Model “Wet and Foam Extinguisher Type” Put on safety glasses. A plastic spray bottle is filled to half with concentrated sodium carbonate solution. A small test tube, which contains a few milliliters of concentrated sulfuric acid, is put into the solution in a way that it swims. The bottle is shut with a capillary glass tube. Close to a sink, the spray bottle is briefly inverted; the spurt of the spray bottle is pointed into the drain: the content of the extinguisher model empties itself with a cutting spurt. In a repetition of this experiment, foam concentrate can be mixed to the sodium carbonate solution: model experiment of a foam extinguisher. Caution in the disposal: remains of concentrated sulfuric acid!

• E8.16 Alcohol Test “Chromate Type” One alcotest tube is prepared; a small amount of alcohol is spread in the mouth and ethanol vapor is blown with the breathing air through the tube into a synthetic plastic bag: the color in the indicator zone turns from yellow to green.

  A yellow-colored potassium chromate solution (T/N) is acidified, and a small amount of ethanol (F) is added: a color change from yellow to orange occurs first, then the change from orange to green is observed.