Questions with 1, 2, 3 or 4 marks usually start with command words. If a question starts with the command word 'state', 'give', 'name' or 'write down', it needs a short answer only. This type of question can often be answered with one word or phrase.
It is important to state, give, name or write down the number of things that the question asks for. If you write down fewer, you cannot get all the marks. If you write down more, and one is wrong, you might lose a mark.
Some questions start with the command words 'describe', 'explain' or 'compare'. These are often worth two or more marks:
More complex structured questions will be worth three or four marks. They include questions with complex descriptions, explanations and questions in which you need to compare things.
Some of the answers are shown here as bullet points. This is to show clearly how a mark can be obtained. However, do not use bullet points in your answers - the points must be linked together logically.
This page contains AQA material which is reproduced by permission of AQA.
When dilute hydrochloric acid is reacted with sodium hydroxide solution there is a temperature change.
Explain how the temperature changes. [2 marks]
It goes up/increases  because the reaction is exothermic/transfers energy to the surroundings .
Catalysts are used in chemical reactions in industry.
Give two properties of catalysts.
For each property, explain why it makes the catalyst useful in industry. [2 marks]
Catalysts increase rate of reaction , so the products form in less time .
Catalysts lower activation energy , so lowers energy requirements .
Catalysts not used up in the reaction , so only an initial outlay needed .
Only a small amount of catalysts needed , so small initial cost .
One mark is allowed for each property and one mark for each explanation.
The explanation must be linked correctly to the property to gain the mark.
Farmers use ammonium nitrate as a fertiliser.
Farmers want to slow down the rate at which ammonium nitrate fertiliser dissolves in the water in the soil.
Suggest why they spread the fertiliser in the form of small beads instead of a fine powder. [2 marks]
Small beads would dissolve slower than fine powder  because the surface area of the bead is less than fine powder .
The reaction used to make ammonia is:
N2(g) + 3H2(g) ⇌ 2NH3(g)
The forward reaction is exothermic.
At equilibrium, about 35% of the nitrogen and hydrogen are converted to ammonia at 450°C and 200 atmospheres pressure.
Explain the effects of increasing the temperature, or decreasing the pressure, on the amount of ammonia produced at equilibrium. [4 marks]
Increasing the temperature at equilibrium will reduce the amount of ammonia produced  because the reaction is exothermic .
Increasing the pressure at equilibrium will increase the amount of ammonia produced  because the equilibrium will shift towards the smaller number of molecules in the equation (which is ammonia) .