Radioactive materials - Six-mark questions

Six-mark questions will only appear in the Depth paper. There will be two six-mark questions in the Depth paper.

Six-mark questions are extended free-response questions, requiring the longest answers. It is wise to plan your answer rather than rushing straight into it. Without a plan it is easy to stray away from the key point and lose marks, get steps in a process in the wrong order or forget key bits of information.

To gain six marks, you will need to:

  • use appropriate scientific words and terms
  • write your answer in full sentences, not bullet points
  • write clearly, linking ideas in a logical way
  • maintain a sustained line of reasoning, rather than a random list of statements and sentences
  • support explanations using scientific knowledge and understanding

Six-mark questions are marked using a levels-based mark scheme. An answer that is not clear and logically sequenced, and which does not give a coherent argument supported by evidence, will be limited to the lower levels. Similarly, if the question asks you to discuss both sides of an argument, or explain two observations, you will be limited to the lowest level if your answer only considers one of them (no matter how brilliantly written or comprehensively explained that one is!).

Sample question 1 - Foundation

Question

Nuclear power today is generated by nuclear fission.

Some scientists believe that in the future nuclear fusion will be a major source of energy.

Use the structure of the atom to explain the process of nuclear fusion.

You may use the blank space to draw a diagram to help your explanation. [6 marks]

OCR 21st Century Science, GCE Physics, Paper A182, June 2013.

Nuclei are the centre of atoms and contain protons and neutrons. In nuclear fusion, nuclei of hydrogen are brought together at high temperatures. They fuse to make larger helium nuclei. This process releases lots of energy. Because the nuclei are positively charged, they would normally repel. A large amount of energy is needed to overcome this repulsion and make the nuclei fuse together. Therefore, nuclear fusion is done in a magnetic container at high temperatures.

To get into the five to six mark band for this question there needs to be a well-developed line of reasoning and your answer needs to be clear and logically structured. A good idea is to plan your response before writing it - write down what a nucleus consists of and the process of nuclear fusion. When writing your answer, write in clear concise language and full sentences.

Sample question 2 - Higher

Question

Priya is going to work in a laboratory where radioactive sources are used.

She knows that radioactive sources can be dangerous.

Her supervisor has reassured her that the risk is low if she follows the safety procedures.

Here are some safety procedures:

  • wear disposable gloves
  • use long-handled tongs to handle the sources
  • wear a monitoring badge

What are the risks from handling radioactive sources and how do these safety procedures reduce the risks? [6 marks]

OCR 21st Century Science, GCE Physics, Paper A182, June 2015 - Higher.

Radioactive sources emit ionising radiation. This can damage human cells and DNA, which could cause cancer. Radiation ionises molecules, which can take part in chemical reactions. A person handling radioactive sources is at risk from contamination and irradiation. The gloves provide a barrier which will help prevent contamination and also prevent irradiation from alpha sources.

The tongs increase the distance between the person and the source, which will also prevent direct contact and contamination by the source. The amount of radiation received from a source decreases by the square of the distance, eg doubling the distance reduces exposure by a factor of four. Tongs can also allow the user to direct the source away from them, preventing irradiation.

Monitoring badges will monitor exposure over time and will inform the user when they need to avoid further exposure. Some monitoring badges provide an instantaneous warning if safe levels are exceeded.

When answering this question it is important to cover all aspects of the question. Make sure that you mention the risks involved in handling radioactive sources and explain how each of the safety precautions mentioned reduces the risks.