Radioactive Decay (Edexcel GCSE Physics)

Exam Questions

2 hours11 questions
1a
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1 mark

When carbon-14 decays it emits a beta-minus particle.

A beta-minus particle is

A an electron
B a neutron
C a positron
D a proton
1b
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3 marks

The word box contains the names of different types of radiation.

alpha radiation infrared gamma rays
microwaves X-rays beta radiation

Write the name of each type of radiation in the correct section of the diagram in Figure 1.

6-2-e-1b-radioactive-decay-venn-diagram-edx-gcse

Figure 1

1c
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4 marks

State the type of radiation that

(i)
can penetrate a few mm of aluminium
[1]
(ii)
is the most ionising
[1]
(iii)
is a type of electromagnetic radiation
[1]
(iv)
has a negative charge
[1]
1d
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1 mark

Everyone is exposed to background radiation. One source of background radiation is radon gas.

State another source of background radiation.

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2a
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2 marks

Actinium-225 is a radioactive isotope which emits alpha radiation when it decays.

Complete the table for the particles that make up an alpha particle.

name of particle number of particles
proton  
  2
2b
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2 marks

The nucleus of an atom of actinium-225 can be represented by the symbol

begin mathsize 24px style Ac presubscript 89 presuperscript 225 end style

Use numbers from the box to complete the following sentences.

87       91       221       229

 

When actinium-225 emits an alpha particle

the nucleon number becomes ..........................

the proton number becomes ..........................

2c
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2 marks

Actinium-225 has a half-life of 10 days.

State the definition of half-life.

2d
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3 marks

The mass of a sample of actinium-225 is 400 mg.

(i)
State the number of half-lives in 20 days
[1]
(ii)
Determine the mass of actinium-225 after 20 days.
[2]

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3a
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4 marks

Some atomic nuclei are unstable.

Complete the sentences about radioactive decay using the words from the box. 

reducing protons radiation molecules
random neutrons planned visible light

     

Some isotopes are unstable because of their large size or because they have too many or too few .................... .

Unstable nuclei can emit .................... to become more stable.

As this moves away from the nucleus, it takes some energy with it .................... the overall energy of the nucleus and making the nucleus more stable.

Radioactive decay is a .................... process. This means it is not possible to know exactly when a particular nucleus will decay.

3b
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4 marks

Complete the table for the correct properties of the four different types of radiation.

Particle Composition Mass / u Charge / e
Alpha 2 protons
2 neutrons
   
Beta-minus     −1
  positron (e+) 0.0005  
    0 0

3c
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1 mark

Cobalt-60 decays to nickel-60 through the process of radioactive decay.

Co presubscript 27 presuperscript 60 space rightwards arrow space Ni presubscript 28 presuperscript 60 space plus space straight X

State the name of particle X.

3d
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6 marks

Background radiation comes from a variety of sources, some are natural and some are man-made.

Place a tick (✔) in each row to indicate whether the source is man-made or natural.

  man-made source natural source
fallout from nuclear weapons    
cosmic rays    
nuclear waste & accidents    
carbon-14 in biological material    
radon gas    
medical sources    

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1a2 marks

Figure 8 shows the symbol for the nucleus of an atom of strontium‐90.

fig-8-paper1f-june2020-edexcelphysics
Figure 8
i)
How many protons are in the nucleus of an atom of strontium‐90?

[1]

  A 38
  B 52
  C 90
  D 128

ii)
How many neutrons are in the nucleus of an atom of strontium‐90?

[1]

  A 38
  B 52
  C 90
  D 128
1b2 marks

The half‐life of strontium‐90 is 29 years.

The table in Figure 9 gives some information about how the mass of a sample of strontium‐90 changes with time.

mass of strontium-90 in g time in years
1600 0
............................................ 29
400 ............................................

Figure 9

Complete the table in Figure 9.

1c7 marks
A teacher sets up an experiment to show some students how far beta particles travel in air.

Figure 10 shows some of the equipment she uses.

fig-10-paper1f-june2020-edexcel-gcse-physics

Figure 10

i)
State the scientific name for the radioactivity detector shown in Figure 10.

[1]

The teacher also has:

• a radioactive source that emits only beta particles
• a metre rule.

ii)
State two precautions the teacher must take to protect herself from the effects of radioactivity.

[2]


1..............................................................................................................................................................................................................

2..............................................................................................................................................................................................................

iii)
Describe how the teacher could show how far beta particles travel in air.

[4]

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2a4 marks

Figure 4 shows a Geiger-Müller (GM) tube used for measuring radioactivity.

fig-4-ipho-1h-june18-qp-edexcel-gcse-physics

Figure 4

Describe how a teacher should use a Geiger-Müller (GM) tube to compare the count-rates from two different radioactive rocks.
2b3 marks

A hospital uses a radioactive isotope with a half-life of 6 hours.


A technician measures a count rate of 80 counts per minute (cpm) from this isotope.

fig-5-ipho-1h-june18-qp-edexcel-gcse-physics
Figure 5

Complete the graph on Figure 5, as accurately as possible, to show how the count-rate from this isotope will change from the time of the first measurement.

The first point is already drawn in Figure 5.

2c1 mark

One radioactive source used in hospitals is technetium (Tc).


Technetium is produced from the radioactive decay of molybdenum (Mo).

Complete the following nuclear equation.

Mo presubscript 42 presuperscript 99 space rightwards arrow space space space space Tc space plus space straight beta presubscript negative 1 end presubscript presuperscript 0

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3a6 marks

Energy from the nuclei of atoms can be used in medical diagnosis and treatment.

i)
Fluorine-18 is a radioactive isotope used in PET scanners for medical diagnosis.

Explain why fluorine-18 must be produced close to the hospital where it is used.

[2]

ii)
Some tumours inside the body can be treated by using either alpha radiation or gamma radiation.


Explain why the source of alpha radiation is usually inside the body but the source of gamma radiation can be outside the body.

[4]

3b4 marks
i)
In a controlled chain reaction of uranium-235, which of these could cause a uranium-235 nucleus to undergo fission?
[1]
  A an alpha particle
  B a beta particle
  C a neutron
  D a proton

ii)
The kinetic energy of one of the particles released in a fission reaction is 1.2×10–11 J.

The mass of the particle is 1.4×10–25 kg.

Calculate the velocity of the particle.
[3]

velocity of the particle = .............................................................. m/s

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4a6 marks

Complete the table with the correct properties of alpha, beta and gamma radiation.

Particle Composition Mass Charge
Alpha 2 protons and 2 neutrons    
Beta   0  
Gamma     0
4b
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2 marks

Plutonium−239 decays to uranium−235 through the emission of an alpha particle.

Determine the missing values in the decay equation:

 
Pu presubscript 94 space end presubscript presuperscript 239 space end presuperscript rightwards arrow straight U presubscript 92 space end presubscript presuperscript left parenthesis straight i right parenthesis space end presuperscript plus straight alpha presubscript left parenthesis ii right parenthesis end presubscript presuperscript 4 space end presuperscript

 

4c2 marks

Strontium−90 decays through beta−minus decay to form Yttrium−90.

Determine the missing values in the decay equation.

 

Sr presubscript 38 space end presubscript presuperscript 90 space end presuperscript rightwards arrow straight Y presubscript left parenthesis straight i right parenthesis end presubscript presuperscript 90 plus beta presubscript negative 1 space end presubscript presuperscript open parentheses ii close parentheses space end presuperscript

4d4 marks

Fluorine−18 decays through beta−plus decay to form oxygen−18.

(i)
Describe what happens in beta-positive decay.
[2]
(ii)
Determine the missing values in the decay equation.
 

straight F presubscript 9 space end presubscript presuperscript 18 space end presuperscript rightwards arrow straight O presubscript 8 presuperscript left parenthesis ii right parenthesis end presuperscript plus beta presubscript left parenthesis iii right parenthesis space end presubscript presuperscript 0 space end presuperscript

[2]

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5a
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2 marks
Define half−life.
[2]
5b5 marks

A student investigates the half−life of technetium with time. The box shows some of the variables in the experiment.

 
time distance form the detector to the sample sample size
same material for the sample radioactive activity
 

Using words from the box above:

(i)
State the independent variable
[1]
(ii)
State the dependent variable
[1]
(iii)
State the control variables for the experiment
[3]
5c4 marks

The experiment uses a variety of apparatus. Draw a line to match the apparatus with its correct use.

7-1-q5c-question-sl-sq-easy-phy
5d
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3 marks
The student plots the following graph of their results.

6-2-m-5d-half-life-of-a-sample

Determine the half−life of the sample.

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1a
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1 mark

This question is about radioactivity.

Alpha (α), beta (β) and gamma (γ) are three types of radioactive emissions.

Which statement describes all of these radioactive emissions?

  A ionising and emitted by stable nuclei
  B ionising and emitted by unstable nuclei
  C neutral and emitted by stable nuclei
  D neutral and emitted by unstable nuclei
1b2 marks

Fluorine-19 is a stable isotope of the element fluorine

The element fluorine also has several radioactive isotopes.

Describe one similarity and one difference between the numbers of particles in one nucleus of fluorine-19 and one nucleus of a radioactive isotope of fluorine.


similarity ...........................................................................................................................................................

difference ..........................................................................................................................................................

1c4 marks

Figure 3 shows a Geiger-Muller (G-M) tube attached to a counter.
The G-M tube is used to measure the activity of a source of beta (β) radiation.
There is an aluminium sheet between the beta source and the G-M tube.
The counter is switched on and after 1 minute shows a count of 268.

fig-3-paper1h-oct2021-edexcel-gcse-physics

Figure 3

i)
The aluminium sheet is taken away.
The counter is reset to zero and then switched on again.
A new count is taken for 1 minute.

Explain why the new count is greater than 268.

[2]

ii)
The beta source is then also taken away.
The counter is reset to zero and switched on again.
A new count is taken for 1 minute.

Give a reason why there would now be a reading on the counter.

[1]

iii)
State the SI unit for the activity of a radioactive source.

[1]

1d2 marks

Radium-223 is a radioactive substance.

Radium-223 is an alpha emitter.

The half-life of radium-223 is 11 days.

A radioactive source contains 1.7 × 1023 nuclei of radium-223.

Calculate the number of radium-223 nuclei remaining in the source after a time of 33 days.

number of radium-223 nuclei remaining = .............................................................

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2a2 marks

Sometimes food can become contaminated with radioactive substances.

Describe the harmful effects of eating food contaminated with radioactive substances.

2b2 marks

Gamma radiation can be used in food processing to irradiate food.

Explain why some food is irradiated with gamma radiation.

2c1 mark

Gamma radiation is part of the electromagnetic spectrum.

When the nucleus of an atom emits a gamma ray, the number of protons in the nucleus and the number of neutrons in the nucleus do not change.

State how the nucleus does change when it emits a gamma ray.

2d6 marks

Gamma radiation is produced by radioactive decay.

Alpha radiation and beta radiation are also produced by radioactive decay.

Compare the processes of alpha decay and beta decay.

Your answer should include what each radiation is and what effect each decay has on the original nucleus.

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3a1 mark

Which of these describes isotopes of an element?

  A same atomic number different number of neutrons
  B same atomic number different number of protons
  C same mass number different number of neutrons
  D same mass number different number of protons

3b1 mark
Figure 9 represents a decay that can happen inside the nucleus of an atom.

fig-9-paper1h-june2020-edexcel-gcse-physics

Figure 9

Which decay is represented in Figure 9?

  A alpha
  B beta minus
  C beta plus
  D gamma

3c
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3 marks

The half-life of cobalt-60 is 5 years.
A school cobalt source had an activity of 38.5 kBq in the year 2000.
Estimate the activity of this source in the year 2020.



activity = .............................................................. kBq

3d2 marks
Explain what can happen to the body if a person has a prolonged exposure to gamma rays.
3e4 marks

A G-M tube is connected to a counter.
A teacher places the G-M tube near to a radioactive source.
A student starts the counter and clock at the same time and writes down the readings shown on the counter every 15 s.

The student plots the readings with a line of best fit, as shown in Figure 10.

fig-10-paper1h-june2020-edexcel-gcse-physics

Figure 10

i)
Calculate the average count rate, in counts/s, from the graph.
Show your working on the graph.

[2]


average count rate = .............................................................. counts/s

ii)
The student says that the experiment must have been done carelessly because the data seemed quite scattered away from the best fit line.
 

The teacher claims such results should be expected in radioactivity experiments.
Justify the teacher’s claim.

[2]

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