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GCSE Biology · key term
A cloudy mixture of tiny droplets of one liquid dispersed through another liquid.
Used by AQA, Edexcel and OCR
Specification 4.2.2.1 · Paper 1
Revise: Required Practicals: Food Tests and Amylase ActivityA qualitative test identifies whether a type of molecule is present from an observable result, such as a colour change or a cloudy emulsion. It does not by itself give an exact concentration.
Specification 1.13B · Paper 1, Paper 2
A cloudy mixture in which tiny droplets of one liquid are dispersed through another liquid.
Revise: Food Tests InvestigationA reagent reacts with a particular type of substance and produces an observable result, such as a colour change, precipitate or emulsion.
Specification PAG 2 · Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
A cloudy mixture of tiny droplets of one liquid dispersed in another; a white emulsion is a positive result in the ethanol test for lipids.
Revise: Testing for biological moleculesFor the ethanol emulsion test for lipids, mix the food sample with a few cubic centimetres of ethanol, then pour the mixture into distilled water. A white, cloudy emulsion indicates lipids. An alternative described in the practical notes is to let a drop of sample dry on sugar paper: a translucent spot that remains when the paper is held to the light indicates lipid.
A cloudy white emulsion is a positive lipid result. Ethanol itself is colourless, so “ethanol turns white” is less precise than describing the emulsion formed after the extract is added to water.
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