Testing for Saturation (Oxford AQA IGCSE Chemistry)

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

1. Use the dropping pipette to add 1 cm³ of each liquid into a test tube

2. To tube A, add 5 drops of bromine water and add the bung

3. Shake the tube for 5 seconds

4. Observe your results

5. 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: 

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