Questions

Q1.
 
(a)  The table shows how the activity of a sample of plutonium-238 varies with time.

(i)  Plot a graph of activity (y-axis) against time (x-axis).
(4)
(ii)  Draw the curve of best fit.
(1)

(iii)  Use your graph to find the half-life of plutonium-238.
Show your working.
(2)

half-life = ........................................................... years
(b)  Plutonium-238 transfers thermal energy as it decays. This energy is used to power heater units in spacecraft.
The diagram shows a module from a heater unit.

(i)  Plutonium-238 transfers thermal energy at a rate of 0.56 W for every gram of plutonium.
Calculate the rate of thermal energy output from a pellet of plutonium-238 with mass 2.7 g.
(1)

rate of thermal energy output = ........................................................... W
(ii)  When plutonium-238 decays, it only emits alpha particles.
Explain why a technician can hold a module from the heater unit safely in their hand.
(2)
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(c)  A space probe called Cassini was sent to the planet Saturn on a mission that lasted several years.
Plutonium-238 was used to generate electricity on Cassini.
Explain why it was important to use plutonium-238 rather than another isotope with a shorter half-life.
(2)
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(Total for question = 12 marks)

Q2.
 
Unstable nuclei can emit particles.
(a)  Which of these particles has the largest charge?
(1)
   A    alpha particle
   B    beta particle
   C    neutron
   D    proton

(b)  Which of these particles has the largest mass?
(1)
   A    alpha particle
   B    beta particle
   C    neutron
   D    proton

(c)  The maximum range of a beta particle in air is about
(1)
   A    50 mm
   B    50 cm
   C    50 m
   D    50 km

(d)  When a nucleus emits a beta particle
(1)
   A    the nucleon number decreases by 1
   B    the nucleon number increases by 1
   C    the proton number decreases by 1
   D    the proton number increases by 1

(Total for question = 4 marks)

Q3.
 
(a)  Which of these is an electron?
(1)
   A    an x-ray
   B    a gamma ray
   C    an alpha particle
   D    a beta particle

(b)  (i)  Which of these will repel an alpha particle?
(1)
   A    a nucleus
   B    an electron
   C    a gamma ray
   D    a neutron

(ii)  Which of these could be the path of an alpha particle passing very close to a gold nucleus?
(1)

(iii)  The diagram shows how the different parts of the body affect the radiation from four radioactive sources, A, B, C and D.
Which source only emits alpha particles?
(1)

(iv)  Which of these properties is the reason for using alpha particles in a smoke detector?
(1)
   A    high ionising ability
   B    low mass
   C    short half-life
   D    long range

(Total for question = 5 marks)

Q4.
 
A teacher investigates the half-life of a radioactive isotope that decays quickly.
(a)  The teacher measures the background activity.
Explain how this value should be used in the investigation.
(1)
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(b)  Explain what is meant by the term half-life.
(2)
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(c)  The graph shows how the activity of a sample of the radioactive isotope changes with time.

(i)  Use the graph to find the half-life of the isotope.
(2)
half-life = .................................................. s
(ii)  The teacher takes a new reading every 20 s.
Suggest why the teacher measures the activity so frequently.
(1)
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(Total for question = 6 marks)

Q5.
 
(a)  The table gives some properties of different types of radiation.

(i)  Complete the table by giving the two missing properties.
(2)
(ii)  Which type of radiation from the table has the lowest penetrating power?
(1)
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(iii)  Which types of radiation from the table can be completely absorbed by 5 mm of aluminium?
(1)
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(b)  Carbon-14 is a radioactive isotope of carbon.
It decays by beta emission to form an isotope of nitrogen.
Complete the nuclear equation for the decay of carbon-14.
(2)

(Total for question = 6 marks)

Q6.
 
Most carbon exists in the form of carbon-12, which is a stable isotope of carbon.
Carbon-14 is another isotope of carbon.
Carbon-14 forms in the upper atmosphere when a nitrogen nucleus absorbs a neutron.
(a)  (i)  Complete the nuclear equation for the formation of carbon-14.
(2)

(ii)  Identify particle X.
(1)
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(iii)  Compare an atom of carbon-14 to an atom of carbon-12.
(2)
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(iv)  Carbon-14 is radioactive and decays by emitting β− particles.
Describe what happens to the atomic number and mass number of carbon-14 when it decays.
(2)
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(b)  The graph shows how the activity of a sample of carbon-14 changes with time.
Use the graph to determine the half-life of carbon-14.
(2)

half-life = ........................................................... years
(c)  A scientist uses carbon-14 dating to find the age of a very old wooden bowl.
He uses this method.

·	 take samples of wood of the same mass from the bowl and from a tree
·	 determine the corrected activity for each sample of wood
·	 find the age of the bowl by determining the ratio of carbon-14 in the bowl to carbon-14 in the tree. 
(i)  State why the scientist has to correct the activities.
(1)
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(ii)  State why the scientist takes samples of the same mass.
(1)
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(d)  The scientist is asked to find the age of a dinosaur bone that is about 68 million years old.
Explain why he would not be able to use carbon-14 dating to find the age of the bone.
(2)
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(Total for question = 13 marks)