A Level Biology Lesson 10: Lipids
The Emulsion Test.
Task 1. Check Where this Lesson fits into your Exam Specification!
Task 2. Watch the Revision Notes Lesson in Full.
00:00 Intro Screen / Learning Outcomes
00:53 The Emulsion Test for Lipids - Steps 1-4 overview
01:16 The Emulsion Test Step 1.
01:31 The Emulsion Test Step 2.
01:40 The Emulsion Test Step 3.
01:51 The Emulsion Test Step 4.
02:08 Note 1.
02:36 Note 2.
Download, Print out & complete the accompanying Interactive Worksheet.
A-Level Biology "Lipids: The Emulsion Test" Lesson 10. Summary.
Lipids (fats and oils) are insoluble in water, but they do readily dissolve in ethanol. This property of dissolving fats in alcohol is the basis of the emulsion test.
If your testing a food sample for the presence of lipid follow these steps.
Crush / grind the test sample and add to a test tube with ethanol
Gently mix the sample with the ethanol, ensure all lipid is dissolved in the ethanol.
Decant the dissolved liquid into another test tube containing water.
Observe the results.
A positive result will show a milky / white emulsion.
In preparation for exam style questions on this topic, ensure you know why each step is performed. Understand also that a Bunsen burn is NOT needed for this procedure.
Check Your Spec!
★ AQA Specification Reference: - 3.1 Biological molecules: 3.1.3 Lipids. Students could use, and interpret the results of, the emulsion test for lipids.
★ CIE Specification Reference: - 2 Biological Molecules: Testing for biological molecules. a) carry out tests… the emulsion test for lipids.
★ Edexcel (Biology A – Salters-Nuffield) Specification Reference: - Appendix 5c: Use of apparatus and Techniques. 6. use qualitative reagents to identify biological molecules
★ Edexcel (Biology B) Specification Reference: - Appendix 5c: Use of apparatus and Techniques. 6. use qualitative reagents to identify biological molecules
★ OCR (Biology A) Specification Reference: - 2.1.2 Biological molecules (q) how to carry out and interpret the emulsion test for lipids
★ OCR (Biology B) Specification Reference: - Module 2: Cells, chemicals for life, transport and gas exchange. Use of qualitative reagents to identify biological molecules.
★ WJEC Specification Reference: - Core Concepts 1. Chemical elements are joined together to form biological compounds - SPECIFIED PRACTICAL WORK - Food tests to include: emulsion test for fats and oils.