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 structured 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 and 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.
Ethene can be produced from long-chain hydrocarbons by cracking.
Give the conditions needed for cracking. [2 marks]
Crude oil is a mixture of many different carbon compounds.
Crude oil can be separated into useful fractions by fractional distillation.
The image shows a column used to separate crude oil.
Why does kerosene separate out of the mixture before diesel oil? [1 mark]
The boiling point of kerosene is lower .
The table shows the carbon dioxide emissions of four fuels used to generate electricity.
|Fuel||Direct CO₂ emissions in kg per MWh||Lifecycle CO₂ emissions in kg per MWh|
Direct CO2 emissions are the amounts of carbon dioxide released when the fuel is burned.
Lifecycle CO2 emissions is the total amount of carbon dioxide released during all stages from fuel extraction to when the fuel has been used.
Use the data from the table to explain why wood is considered to be a low carbon dioxide emitting fuel. [2 marks]
Although wood has higher direct emissions than other fuels , it has much lower lifetime emissions .
Electricity in the UK is generated in many ways.
The image below shows an undersea turbine.
The undersea turbine uses tidal energy to generate electricity.
Explain two advantages of using undersea tidal turbines to generate electricity rather than fossil fuels. [4 marks]
Any two from the following. In each case you will be awarded a mark for a statement and a mark for a correctly linked reasoning: