Three and four mark questions

These are similar to one and two mark questions but you will be expected to write in more depth for three and four mark questions.

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Three and four mark questions usually require longer answers.

The answers here give lists of valid points that could be included in your answer.

This page contains AQA material which is reproduced by permission of AQA.

Sample Question 1 - Foundation

Question
Helium ion, two neutrons, two protons and no electrons.

What is the charge on the helium atom in the figure?

Explain your answer. [3 marks]

It is neutral [1] because protons have positive charge and electrons have negative charge [1] and there are equal numbers of protons and electrons [1].

The three marks indicate that more detail is needed than just stating the overall charge or the numbers of particles. Both the numbers of particles and their charges should be included.

Sample Question 2 - Higher

Question

Technetium-99 used in hospitals emits gamma radiation and has a half-life of 6 hours.

After treatment, hospital equipment may become contaminated.

Describe the level of the hazard associated with contamination with technetium-99.

You should include in your answer a description of how the level of hazard changes over time. [3 marks]

Initially there is a high level of hazard (activity initially high) [1]. The level of hazard drops to a low level quickly (drops to safe level quickly) [1] due to short half-life [1].

It is important in this question to recognise that 6 hours is a relatively short half-life. Some radioisotopes have a half-life of millions of years.

Sample Question 3 - Higher

Question

Transmutation is the name given to a process where one element changes into another.

Explain and compare how two different types of radioactive decay can cause transmutation. [4 marks]

In alpha decay, two protons and two neutrons are emitted from the nucleus as an alpha particle meaning the atomic number decreases by two [1]. In beta decay, a neutron turns into a proton and emits an electron meaning the atomic number increases by one [1]. In both cases the proton number has changed [1] meaning a new element is formed [1].

This could be summarised by the following list:

Beta decay:

  • atomic number increases by one
  • a neutron decays into a proton

Alpha decay:

  • atomic number decreases by two
  • an alpha particle is emitted

Comparison:

  • both change number of protons (hence new element/transmutation)
  • beta decay increases atomic number, alpha decay decreases it