Elements, compounds and mixtures - Practical questions
You will complete eight Practical Activity Groups (PAGs) if you are studying GCSE Chemistry. If you are studying GCSE Combined Science you will complete 16, of which five are in Chemistry.
You could be asked questions about the apparatus, methods, safety precautions, results, analysis and evaluation of these experiments.
There are two PAGs in the Elements, compounds and mixtures section:
- separation techniques, eg use chromatography to identify the mixtures of dyes in an unknown ink
- distillation, eg distil a mixture such as inks or orange juice
These questions have been written by a Bitesize consultant as a suggestion to the type of questions that may appear in an exam paper.
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Dr Alex Lathbridge answers questions about practicals.
Sample question 1 - Higher
Question
Ethanol is a flammable liquid that boils at 78 掳C. It mixes completely with water, which boils at 100 掳C. Give a suitable method to produce a concentrated solution of ethanol from a mixture of ethanol and water. Explain a precaution to reduce the risk of harm when carrying out this separation.
[3 marks]
The following are valid points that could be included in your answer. It is important that you do not bullet point your answer but write your sentences in full.
- fractional distillation [1 mark]
- heat the mixture with an electric heater [1 mark]
- do not use a Bunsen burner flame as it could ignite the ethanol [1 mark]
Sample question 2 - Higher
Question
Copper sulfate is soluble in water but glass is not. A glass bottle containing solid copper sulfate breaks. A student tries to produce copper sulfate crystals from the mixture of glass and copper sulfate. This is the method the student uses:
- add cold water to the mixture and stir
- pour the liquid into an evaporating basin
- heat the basin with a Bunsen burner until copper sulfate crystals form
Suggest two improvements to the student鈥檚 method.
[2 marks]
The following are valid points that could be included in your answer. It is important that you do not bullet point your answer but write your sentences in full.
- use warm water at step 1 [1 mark]
- use filtration at step 2 [1 mark]