Testing for Saturation (Oxford AQA IGCSE Chemistry) : Revision Note
Testing for Saturation
Objective
To test for the presence of a double bond in an unknown hydrocarbon.
Apparatus
Four unknown samples of hydrocarbons labelled A, B, C and D
Bromine water
Bungs for test tubes
Test tubes and test tube rack
Dropping pipettes
Method
Use the dropping pipette to add 1 cm3 of each liquid into a test tube
To tube A, add 5 drops of bromine water and add the bung
Shake the tube for 5 seconds
Observe your results
Repeat steps 2 - 4 for tubes B, C and D
Equipment set up
Practical Tip
This practical must be carried out in a fume cupboard as the fumes of bromine water can be toxic.
Make sure the bungs are properly inserted into the test tubes before shaking to prevent spillages.
Results
Record your results for each test carefully in a suitable table like this:
Sample | Observations in bromine water |
|---|---|
A | |
B | |
C | |
D |
Evaluation
Once you have recorded the results from the tests, use them to identify whether the hydrocarbon is saturated or unsaturated
Unsaturated hydrocarbons will cause the bromine water to turn colourless
Saturated hydrocarbons will not react with the bromine water so the solution remains orange
Worked Example
A student was given five samples labelled A-D.
The following set of results were obtained from adding bromine water to the samples.
Sample | Observations in bromine water |
|---|---|
A | remains orange |
B | orange to colourless |
C | remains orange |
D | orange to colourless |
Identify the samples that contain double bonds.
Answer:
The samples that contain double bonds are B and D because they have turned colourless.
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