Physics GCSE: Radioactivity

Exam-Style Questions

1.      a) Explain what the following represent:

          i) The Mass or Nucleon number.

          ii) The Proton or Atomic number.

     b) State the two possible causes of radioisotopes.

     c) What charges do Alpha, Beta and Gamma radiation possess?

(Marks available: 7)

 Answer outline and marking scheme for question: 1

     a)  i) It tells you how many particles are in the nucleus, i.e. how many protons and neutrons.

          ii) It tells you how many protons there are in the nucleus.

(2 Marks)

     b) Too much energy.

         The wrong number of particles in the nucleus.

(2 Marks)

     c) Alpha has a positive +2 charge, Beta has a negative -1 and Gamma has no charge.

(3 Marks)

(Marks available: 7)

2.      The diagram shows the 'plum pudding' model of an atom.

   a) Scientists thought that the 'pudding' was positively charged.

      i) Name the particles labelled A in the diagram.

(1 Mark)

      ii) Complete this sentence by choosing the correct words from the box.

       negatively Charged   positively charged   uncharged

      The particles labelled A are ......................................

(1 Mark)

   b) A new model of an atom was suggested by Rutherford and Marsden. They fired alpha particles at thin metal foil. Alpha              particles are positively charged. In their model each atom has a nucleus. The diagram below shows the path of an alpha              particle as it passes the nucleus of an atom.

Explain why the alpha particle changes direction

(2 Marks)

(Marks available: 4)

 
Answer outline and marking scheme for question: 2

     a)  i) electrons

(1 Mark)

          ii) negatively charged (no e.c.f)

(1 Mark)

     b) nucleus is positive/ alpha and nucelus have same charge

(1 Mark)

        (like) charges repel/push away

(1 Mark)

(Marks available: 4)

3.      Radon is a radioactive gas. It escapes from the underground rocks and causes a large part of the natural background                 radiation in the United Kingdom.

     a) Radon-220 

(	220	Rn)
	86

         i) How many protons are there in a nucleus of radon-220?

(1 Mark)

        ii) How many neutrons are there in a nucleus of radon-220?

(1 Mark)

       iii) Explain what is meant by the statement: "This element has three isotopes".

(2 Marks)

    b)

• Radon-220 has a short half-life and emits a-particles
• Alpha particles are easily stopped by material and only travel a short distance in air.
• Radon gas is thought to produce harmful effects.

         When home owners, in areas where radon gas is produced, were told of the risks, very few too notice.

       i) Explain why the presence of radon gas in buildings is a health hazard.

(3 Marks)

       ii) Discuss why, you think, so few people took any action to reduce the risks due to radon gas.

(4 Marks)

(Marks available: 11)

 
Answer outline and marking scheme for question: 3

   a) i) 86

(1 Mark)

      ii) 134

(1 Mark)

      iii) An explanation to include particles with:

• same number of protons
• Different number of neutrons

(2 Marks)

  b) i) An explanation to inlcude:

• gas breathed in
• a - particles cannot pass through living tissue
• named health risk

(3 Marks)

    ii) A discussion to include three of:

• lack of understanding of dangers
• evidence
• cost
• information not widely known
• complacency
• information did not spell out dangers clearly
• regional variation

(4 Marks)

(Marks available: 11)

4.      Kate's teacher wants to find how much beta radiation passes through different thicknesses of aluminium.

First he measures background radiation.

It gives a reading of 60 counts per minute on the ratemeter.

   a) Suggest two possible sources of background radiation.

(2 Marks)

   b) Write down two safety precautions that he should take when using the beta source.

(2 Marks)

   c) Aluminium is rolled into sheets twenty millimetres thick in a rolling mill.

A radioactive source and a detector are used to check the thickness of the sheet as it leaves the rollers.

     i) Why is beta radiaton not suitable for checking tewnty millimetre sheet?

(1 Mark)

     ii) Suggest one type of radiation which could be used to check the thickness of twenty millimetre sheet.

(1 Mark)

     iii) The radioactive isotope used has a half-life of 5.3 years. Explain what is meant by the term half-life.

(1 Mark)

     iv) One rolling mill uses 20 mg of this isotope as the source.

          What will be the mass of this radioactive isotope in the source 10.6 years later?

           mass = _____________ mg

(1 Mark)

     v) It would be sensible to use, in the rolling mill, a radioactive isotope with a half-life much shorter than 5.3 years. Explain              why.

(2 Marks)

(Marks available: 10)

 
Answer outline and marking scheme for question: 4

   a) cosmic rays/ sun (1)

       rocks/ granite (1) power stations (1) radon (1) falout/ nucelar accidents (1) nuclear weapons testing/ atomic bombs (1)

      Choose any two

(2 Marks)

   b) distance/ use tongs (1)

       suitable reference to shielding (1) short time of exposure (1) minimum source strength (1) pupils not to handle source (1)

      Choose any two

(2 Marks)

   c) i) beta radiation will not pass through/ stopped by 20 mm thick sheet/ sheet too thick

(1 Mark)

     ii) gamma/ x-rays

(1 Mark)

     iii) time for decay rate/ number of radioactive nuclei to halve

(1 Mark)

     iv) 5 mg

(1 Mark)

     v) count rate becomes too low for thickness checking/ becomes too low too quickly (1)

         source needs to be frequently changed (1)

        detector neds to be frequently calibrated (e.g. appreas to be thicker than it is)/ need a fairly constant count rate (1)

sensible consequence e.g. effect on sheet thickness (1)

Choose any two

(2 Marks)

(Marks available: 10)

5.      a) Why can some isotopes of atoms be unstable?

(1 Mark)

      b) What is a Geiger-Muller?

(1 Mark)

      c) List three purposes of using radioactivity and how it is used

(3 Marks)

(Marks available: 5)

 
Answer outline and marking scheme for question: 5

      a) too much energy/ wrong number of particles in the nucleus

(1 Mark)

      b) Collects the charged ions and can measure the amount of ionisation that is taking place in a certain time by radioactive substances.

(1 Mark)

     c) Collects the charged ions and can measure the amount of ionisation that is taking place in a certain time by radioactive                substances.

        Medicine - to kill cancer

        Industry - to detect thickness of materials

        Dating Materials - used to find out how old things are

(3 Marks)

(Marks available: 5)

6.      a) At the end of the nineteenth century, physicists considered that the atom consisted of evenly distributed electrons and                 protons.

         i) Which famous experiement, at the start of the twentieth century, suggested the exostence of the nucleus?

(1 Mark)

        ii) Give an outline of what the experiment involved and how the results led to this the nuclear model of the atom.

(4 Marks)

        iii) Protons and electrons were initially considered to be fundamental particles.

Explain what this term means and state which of the two particles named is still considered to be a fundamental particle.

(2 Marks)

      b)The neutron was deteced much later than either the electron or the proton although it was known to exist.

          i) Suggest why neutrons were much more difficult to detect than protons or electrons.

(2 Marks)

         ii) Quarks are fundamental particles. What is the connection between quarks, protons and neutrons?

(2 Marks)

(Marks available: 11)

 
Answer outline and marking scheme for question: 6

a) i) a-particles scttering/ Rutherford. Geiger Marsden experiment

(1 Mark)

    ii) An outline to include:

• α particles fired at gold foil
• angles of scatter measured
• a few scattered through large angles

(4 Marks)

    iii) An explanation to include:

• canot be divided/ broken down further
• electrons

(2 Marks)

b) i) A suggestion to include:

• neutrons have no charge/ cannot be deflected by E/B fields
• (difficult to detect) travel through matter easily

(2 Marks)

    ii) protons and neutrons contain 3 quarks;

different combinations of up and down quarks

(2 Marks)

(Marks available: 11)