![]() ![]() Test all the substances in the same way to find out which acts as an emulsifier.(Suggested emulsifiers to test are: flour, sugar, mustard powder, egg white, egg yolk, a range of different detergents.) Repeat the experiment but add a small quantity of one of the substances you are testing before you shake the tube.Remove the bung and leave the mixture to stand. Put a bung into the top of the tube and shake it – but not too vigorously. Put about 2 cm 3 of oil into a boiling tube.Due to the salmonella risk, handling raw egg should be kept to a minimum, so provide disposable pipettes with the egg for students to transfer it to the boiling tubes. Ensure no yolk contaminates the white – the other way round is less important. If you use fresh eggs it is fairly easy to separate these.Colman’s powder is good and powder lasts far longer than ordinary mustard so can be used from year to year.Cheaper detergents do not usually work very well.Corn oil is good because it is dark in colour and easier to see.The boiling tubes must be very clean and must not be contaminated with detergent. Using boiling tubes rather than test-tubes means that more chemicals are consumed, but it is easier to see what is going on and much easier to clean up.Read our standard health and safety guidance.Note: other substances can be used if preferred. Boiling tubes and bungs (see note 2 below).Raw egg should be handled as little as possible, and a disposable pipette should be used to transfer it to the boiling tubes. Eggs have a salmonella risk and should be marked with the lion symbol. Students should be warned against tasting anything – eg the sugar – in the laboratory. They should be encouraged to record the results clearly, which probably means a results table. It is probably worth ensuring that students understand the meaning of the terms ‘emulsifier’ and ‘emulsion’ before they begin. This experiment is very straightforward and does not take very long, although if students shake the boiling tubes too vigorously then the mixtures can take a while to separate. Colloids such as these are often found in foods. In this simple activity, students test a range of substances commonly found in the kitchen to see which ones stabilise an oil and water emulsion. RSC Yusuf Hamied Inspirational Science ProgrammeĪ mixture of oil and water usually separates quickly, but a range of substances act as emulsifiers.Introductory maths for higher education.The physics of restoration and conservation. ![]()
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