Question 4 (higher question)

Electrolysis of acidified water can produce hydrogen and oxygen.

The apparatus for the electrolysis is:

. water containing some dilute sulfuric acid

• two graphite rods

• a suitable container for the electrolysis reaction

. a suitable source of electricity

• test tubes

Describe how to use the apparatus to electrolyse acidified water, and how to test the gases to

show that they are hydrogen and oxygen. Include a diagram in your answer. [6 marks]

Describe means you should recall facts, events or processes accurately. You might need to give an account of what something looked like, or what happened.

Explain means you need to make something clear, or state the reasons for something happening.

Compare means you need to describe similarities and differences between things. If you are asked to compare X and Y, write down something about X and something about Y, and give a comparison. Do not just write about X only or Y only.

Evaluate means you must use information supplied, or your own knowledge, to consider the evidence for and against or to identify strengths and weaknesses. You must then complete your answer with a conclusion, stating which is better and why, for example.