· web view(b) exposure to radon gas can cause lung cancer.a recent study has compared the risk of...

11 Atomic Structure and Radiation

223 minutes

223 marks

Q1. The diagram represents an atom of beryllium.

(a) Complete the following statements by writing one of the letters, J, K or L, in each box.

Each letter should be used only once.

The particle with a positive charge is

The particle with the smallest mass is

The particle with no charge is

(2)

(b) Give the reason why all atoms have a total charge of zero.

........................................................................................................................

........................................................................................................................(1)

(c) Complete the following sentence.

There are several isotopes of beryllium. Atoms of different beryllium

isotopes will have different numbers of ........................................................(1)

(d) What happens to the structure of an atom to change it into an ion?

........................................................................................................................

........................................................................................................................(1)

(Total 5 marks)

Q2. The diagram represents an atom of beryllium. The three types of particle that make up the atom have been labelled.

(a) Use the labels from the diagram to complete the following statements.

Each label should be used once.

The particle with a positive charge is ..........................................................

The particle with the smallest mass is ........................................................

The particle with no charge is ......................................................................

(2)

(b) What is the atomic number of a beryllium atom?

Draw a ring around your answer.

4 5 9 13

Give a reason for your answer.

........................................................................................................................

........................................................................................................................(2)

(c) Which one of the following statements describes what can happen to an atom to change it into an ion?

Tick ( ) one box.

The atom loses a neutron.

The atom loses an electron.

The atom loses a proton.

(1)(Total 5 marks)

Q3.The pie chart shows the average proportions of background radiation from various sources in the UK.

Three sources of background radiation are given in List A.Statements about sources of background radiation are given in List B.

Draw one line to link each source of background radiation in List A to the statement about that source given in List B.

Draw only three lines.

List A List B

Are used to show broken bones.

X-rays

The radiation comes from outerspace.

Cosmic rays

Comes from soil containing aradioactive isotope of potassium.

Radon gas

Gives about 50 % of all backgroundradiation.

(Total 3 marks)

Q4. (a) Carbon has three naturally occurring isotopes. The isotope, carbon-14, is radioactive.An atom of carbon-14 decays by emitting a beta particle.

(i) Complete the following sentences.

The atoms of the three carbon isotopes are the same as each other because

...............................................................................................................

The atoms of the three carbon isotopes are different from each other because

...............................................................................................................(2)

(ii) What is a beta particle and from what part of an atom is it emitted?

...............................................................................................................

...............................................................................................................(1)

(b) Carbon-14 is constantly being made in the atmosphere, yet for most of the last million years, the amount of carbon-14 in the atmosphere has not changed.

How is this possible?

........................................................................................................................

........................................................................................................................(1)

(c) Trees take in carbon-12 and carbon-14 from the atmosphere. After the tree dies, the proportion of carbon-14 that the tree contains decreases.

Graph A shows the decay curve for carbon-14.

(i) Lake Cuicocha in Ecuador was formed after a volcanic eruption.Carbon taken from a tree killed by the eruption was found to have a count rate of 10.5 counts per minute.At the time of the eruption, the count rate would have been 16 counts per minute.

Use graph A to find the age of Lake Cuicocha.

Age of Lake Cuicocha = ............................................. years(1)

(ii) Finding the age of organic matter by measuring the proportion of carbon-14 that it contains is called carbon dating. This technique relies on the ratio of carbon-14 to carbon-12 in the atmosphere remaining constant. However, this ratio is not constant so the age found by carbon dating needs to be adjusted.

Graph B is used to adjust the age of an object found by carbon dating.The value obtained from graph B will be no more than 50 years different to the true age of the object.

Use graph B and the information above to find the maximum age that Lake Cuicocha could be.

Show clearly how you obtain your answer.

...............................................................................................................

...............................................................................................................

Maximum age of Lake Cuicocha = ............................. years(2)

(Total 7 marks)

Q5. (a) The diagram represents a helium atom.

(i) Which part of the atom, K, L, M or N, is an electron?

Part (1)

(ii) Which part of the atom, K, L, M or N, is the same as an alpha particle?

Part (1)

(b) A radioactive source emits alpha particles.

What might this source be used for?

Put a tick ( ) in the box next to your answer.

to monitor the thickness of aluminium foil as it is made in a factory

to make a smoke detector work

to inject into a person as a medical tracer

(1)

(c) The graph shows how the count rate from a source of alpha radiation changes with time.

What is the count rate after 4 hours?

............................................. counts per second(1)

(Total 4 marks)

Q6. (a) Background radiation is all around us all the time.

(i) Radon is a natural source of background radiation.

Name another natural source of background radiation.

...............................................................................................................(1)

(ii) X-rays are an artificial source of background radiation.

Name another artificial source of background radiation.

...............................................................................................................(1)

(iii) An atom of radon-222 decays by emitting an alpha particle.The equation representing the decay is shown below.

How can you tell from the equation that ‘X’ is not an atom of radon?

...............................................................................................................

...............................................................................................................

(1)

(b) Having an X-ray taken increases your exposure to radiation.

The table gives:

• the radiation doses received for 6 different medical X-rays;

• the number of days’ of exposure to natural background radiation each dose is equivalent to.

Medical X-ray Radiation dosereceived

(in arbitrary units)

Equivalent number of daysof exposure to naturalbackground radiation

Chest 2 2.4

Skull 7 8.4

Pelvis 22 26.4

Hip 44 52.8

Spine 140

CT head scan 200 240

A hospital patient has an X-ray of the spine taken.Calculate the number of days of exposure to natural background radiation that an X-ray of the spine is equivalent to.

Show how you work out your answer.

........................................................................................................................

........................................................................................................................

........................................................................................................................

Equivalent number of days = ..................................................(2)

(c) Scientists have shown that X-rays increase the risk of developing cancer.The scientists came to this conclusion by studying the medical history of people placed in one of two groups, A or B.The group into which people were put depended on their X-ray record.

(i) Person J has been placed into group A.Place each of the people, K, L, M, N and O, into the appropriate group, A or B.

Person J K L M N O

MedicalX-ray

record

3 arm None None 2 skull None 4 leg

Group A Group B

J

(1)

(ii) To be able to make a fair comparison, what is important about the number of people in each of the two groups studied by the scientists?

...............................................................................................................

...............................................................................................................(1)

(iii) What data would the scientists have compared in order to come to the conclusion that X-rays increase the risk of developing cancer?

...............................................................................................................

...............................................................................................................(1)

(iv) The chance of developing cancer due to a CT head scan is about 1 in 10 000. The chance of developing cancer naturally is about 1 in 4.

A hospital patient is advised by a doctor that she needs to have a CT head scan.The doctor explains to the patient the risks involved.

Do you think that the patient should give her permission for the CT scan to be taken?


Yes No


...............................................................................................................

...............................................................................................................(1)

(Total 9 marks)

Q7. The diagrams show two different models of an atom.

‘Plum pudding’ model Model used today

(a) The particles labelled ‘X’ in the plum pudding model are also included in the model of the atom used today.

What are the particles labelled ‘X’ ?

..................................................(1)

(b) Scientists decided that the ‘plum pudding’ model was wrong and needed replacing.

Which one of the following statements gives a reason for deciding that a scientific model needs replacing?

Tick ( ) one box.

The model is too simple.

The model has been used by scientists for a long time.

The model cannot explain the results from a new experiment.

(1)

(c) The table gives information about the three types of particle that are in the model of the atom used today.

Particle Relative mass Relative charge

1 +1

very small –1

1 0

Complete the table by adding the names of the particles.(2)

(Total 4 marks)

Q8.The names of three different processes are given in List A.Where these processes happen is given in List B.

Draw a line to link each process in List A to where the process happens in List B.


List A List B

Process Where it happens

in a star

fusion

in a nuclear reactor

chain reaction

in a smoke precipitator

alpha decay

in the nucleus of an atom

(Total 3 marks)

Q9. The diagram shows a system used to control the thickness of aluminium foil as it is being rolled. A radiation source and detector are used to monitor the thickness of the foil.

(a) Which type of source, alpha, beta or gamma, should be used in this control system?

.............................................

Explain why each of the other two types of source would not be suitable.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(3)

(b) The chart shows how the count rate recorded by the detector varies over a short period of time.

Use the graph to explain how the thickness of the foil changes, and how the control system responds to this change.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(c) When first used, the radiation source contains 6 micrograms of strontium-90.The graph shows how the mass of the strontium-90 will decrease as the nuclei decay.

The control system will continue to work with the same source until 75 % of the original strontium-90 nuclei have decayed.

After how many years will the source need replacing?

Show clearly your calculation and how you use the graph to obtain your answer.

........................................................................................................................

........................................................................................................................

........................................................................................................................

Number of years = ........................................(2)

(Total 7 marks)

Q10. (a) The names of the three types of nuclear radiation are given in List A.Some properties of these types of radiation are given in List B.

Draw a straight line to link each type of radiation in List A to its correct property in List B.


List AType of nuclear radiation

List BProperty of radiation

Has the same mass as an electron

Alpha

Very strongly ionising

Beta

Passes through 10 cm of aluminium

Gamma

Deflected by a magnetic field butnot deflected by an electric field

(3)

(b) The diagram shows a system used to control the thickness of cardboard as it is made.

The cardboard passes through a narrow gap between a beta radiation source and a radiation detector.

The table gives the detector readings over 1 hour.

Time Detector reading

08:00 150

08:15 148

08:30 151

08:45 101

09:00 149

(i) Between 08:00 and 08:30, the cardboard is produced at the usual, correct thickness.

Explain how you can tell from the detector readings that the cardboard produced at 08:45 is thicker than usual.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(ii) Which would be the most suitable half-life for the beta source?


six days six months six years(1)

(iii) This control system would not work if the beta radiation source was replaced by an alpha radiation source.

Why not?

...............................................................................................................

...............................................................................................................(1)

(Total 7 marks)

Q11.(a) Atoms of the isotope bismuth-212 decay by emitting either an alpha particle or a beta particle.The equation represents what happens when an atom of bismuth-212 decays by beta emission into an atom of polonium-212.

(i) The bismuth atom and the polonium atom have the same mass number (212).

What is the mass number of an atom?

...............................................................................................................(1)

(ii) Beta decay does not cause the mass number of an atom to change.

Explain why not.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(b) When an atom of bismuth-212 emits an alpha particle, the atom decays into an atom of thallium.

An alpha particle is the same as a helium nucleus.The symbol below represents an alpha particle.

(i) The equation below represents the alpha decay of bismuth-212.

Complete the equation by writing the correct number in each of the two boxes.

(2)

(ii) It is impossible for the alpha decay of bismuth-212 to produce the same element as the beta decay of bismuth-212.

Explain why.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(Total 7 marks)

Q12.The pie chart shows the average proportions of natural background radiation from various sources in the UK.

(a) (i) Complete the following sentence.

On average, .......................................................... of the natural background radiation in the UK comes from radon gas.

(1)

(ii) Radon gas is found inside homes.

The table shows the results from measuring the level of radon gas inside four homes in one area of the UK.

Home Level of radon gas inBq per m3 of air

1 25

2 75

3 210

4 46

Mean 89

One of the homes has a much higher level of radon gas than the other three homes.

What should be done to give a more reliable mean for the homes in this area of the UK?


ignore the data for home number 3

measure the radon gas level in more homes in this area

include data for homes from different areas of the UK

(1)

(b) Each atom of radon has 86 protons and 136 neutrons.

(i) How many electrons does each atom of radon have?


50 86 136 222(1)

(ii) How many particles are there in the nucleus of a radon atom?


50 86 136 222(1)

(Total 4 marks)

Q13.Food irradiation is a process that exposes food to radiation. Irradiation can be used to kill the bacteria that cause food poisoning or to slow down the ripening of fresh fruit and vegetables. Frozen foods and food inside packaging can also be irradiated.

(a) The table gives information about five radioactive isotopes.

Isotope Half-life Radiation emitted

Caesium-134 2.1 years beta

Cobalt-60 5.3 years gamma

Curium-242 160 days alpha

Strontium-90 28 years beta

Technetium-99

6 hours gamma

Which of these radioactive isotopes would be most suitable for irradiating food?

........................................................................................................................

Explain the reasons for your choice.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(3)

(b) Many people think that food should not be irradiated. Consumer groups have said that they are worried about the nutritional value and safety of eating irradiated foods.

(i) Suggest one reason why some people may be concerned about the safety of eating irradiated food.

...............................................................................................................

...............................................................................................................(1)

(ii) Independent scientific committees in several countries, including Sweden, Canada and the UK, have concluded that it is safe to eat irradiated food.

These scientific committees need to be independent from government influence.

Suggest why.

...............................................................................................................

...............................................................................................................(1)

(iii) One group of scientists has compared the vitamin content of non-irradiated foods with irradiated foods.

The table below gives the data obtained for 1 kg of cooked chicken.

Vitamin Non-irradiated foodin milligrams

Irradiated foodin milligrams

B6 1.22 1.35

B12 21.00 28.00

E 3.30 2.15

Niacin 58.00 55.50

Riboflavin 2.10 2.25

Considering only the data in the table, is it valid to conclude that irradiated food is less nutritional than non-irradiated food?

Explain your answer.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(iv) In a restaurant, meals with ingredients that have been irradiated must be clearly identified on the menu.

It is important that people eating in a restaurant are given this information.

Suggest why.

...............................................................................................................

...............................................................................................................(1)

(c) The isotope caesium-137 decays by emitting beta radiation.Caesium-137 has a half-life of 30 years.

(i) What is a beta particle, and from which part of an atom is a beta particle emitted?

...............................................................................................................

...............................................................................................................(1)

(ii) A sample containing caesium-137 has a count rate of 600 counts per minute.

Calculate how long it would take for the count rate from the sample to fall to 75 counts per minute.

Show clearly how you work out your answer.

...............................................................................................................

...............................................................................................................

...............................................................................................................

Time taken = .................................................. years(2)

(Total 11 marks)

Q14. (a) The graph shows how the count rate from a sample containing the radioactive substance cobalt-60 changes with time.

(i) What is the range of the count rate shown on the graph?

From .................... counts per second to .................... counts per second.(1)

(ii) How many years does it take for the count rate to fall from 200 counts per second to 100 counts per second?

Time = .................................................. years(1)

(iii) What is the half-life of cobalt-60?

Half-life = .................................................. years(1)

(b) The gamma radiation emitted from a source of cobalt-60 can be used to kill the bacteria on fresh, cooked and frozen foods. Killing the bacteria reduces the risk of food poisoning.

The diagram shows how a conveyor belt can be used to move food past a cobalt-60 source.

(i) Which one of the following gives a way of increasing the amount of gamma radiation the food receives?


Increase the temperature of the cobalt-60 source.

Make the conveyor belt move more slowly.

Move the cobalt-60 source away from the conveyor belt.

(1)

(ii) To protect people from the harmful effects of the gamma radiation, the cobalt-60 source has thick metal shielding.

Which one of the following metals should be used?


aluminium copper lead(1)

(c) A scientist has compared the vitamin content of food exposed to gamma radiation with food that has not been exposed.

The table gives the data the scientist obtained when she tested 1 kg of cooked chicken.

Vitamin Food not exposedto gamma radiation

Food exposed togamma radiation

Mass in milligrams Mass in milligrams

B6 1.22 1.35

B12 21.00 28.00

E 3.30 2.15

Niacin 58.00 55.50

Riboflavin 2.10 2.25

Considering only this data, which one of the following is a correct conclusion?


Vitamin content is not affected by gamma radiation.

Gamma radiation completely destroys some types of vitamin.

Exposure increased the content of some types of vitamin.

(1)(Total 6 marks)

Q15. The pie chart shows the sources of the background radiation and the radiation doses that the average person in the UK is exposed to in one year.

Radiation dose is measured in millisieverts (mSv).

(a) (i) What is the radiation dose that the average person in the UK receives from radon gas?

...............................................................................................................

...............................................................................................................

Radiation dose from radon gas = ................................... mSv(1)

(ii) A person may receive a higher than average dose of radiation from background sources.

Suggest two reasons why.

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

...............................................................................................................

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

...............................................................................................................(2)

(b) Exposure to radon gas can cause lung cancer.A recent study has compared the risk of getting lung cancer, by the age of 75 years, for cigarette smokers and non-smokers.The people in the study had been exposed throughout their lives to different levels of

radon gas.A summary of the data produced from the study is given in the table.

Exposure to radon gas

Risk of lung cancer by age of 75

Non-smoker Smoker

No exposure 0.4 % 10 %

Moderate exposure 1.0 % 14 %

Very high exposure 1.5 % 32 %

(i) Why were people that have had no exposure to radon gas included in the study?

...............................................................................................................

...............................................................................................................(1)

(ii) Using information from the table, what conclusions can be made about exposure to radon gas and the risk of getting lung cancer?

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(c) At the moment, the regulations designed to protect people from over-exposure to radiation are based on a model called the ‘linear no-threshold’ (LNT) model.Some scientists believe that the LNT model is too simple.These scientists believe that at low radiation levels a process called ‘radiation hormesis’ happens.

The graphs show that each model suggests a link between the risk of developing a cancer and exposure to low levels of radiation.

The link between the risk of developing cancer and exposure to low levels of radiation suggested by each of the models is different.

Describe how.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(d) Scientists have conducted experiments in which mice have been exposed to different levels of radiation. The number of mice developing a cancer has then been measured.

Discuss whether it is ethical to use animals in scientific experiments.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(Total 10 marks)

Q16. The table shows the average background radiation dose from various sources that a person living in the UK receives in one year.

Source of background radiation Average radiation dose received each year in dose units

Cosmic rays (from space) 300

Food and drink 250

Medical treatments (including X-rays) 350

Radon gas 1250

Rocks 350

TOTAL 2500

(a) (i) A student looked at the data in the table and then wrote down four statements.

Only two of the statements are true.

Put a tick ( ) in the boxes next to the two true statements.

More than half of the average radiation dose comes from radon gas.

On average, cosmic rays produce less background radiation than rocks.

Everyone living in the UK receives the same background radiation dose.

Having no X-rays reduces a person’s radiation dose.

(2)

(ii) Each time a chest X-ray is taken, the patient receives about 100 units of radiation.

How many chest X-rays would just exceed the yearly average dose for medical treatments?

........................................................................................................................

Number of chest X-rays = ..................................................(2)

(b) Exposure to radiation can cause cancer.

The graphs, A, B and C, show three different ways that the exposure to radiation and the

risk of getting cancer could be linked.

(i) What do all three of these graphs suggest happens to the risk of getting cancer when the radiation dose goes from moderate to high?

...............................................................................................................

...............................................................................................................(1)

(ii) Some scientists believe that exposure to low radiation doses reduces the chance that a person will get cancer. This effect is called ‘radiation hormesis’.

Which one of the graphs, A, B or C, shows ‘radiation hormesis’?

Write your answer in the box.


...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(c) Scientists did an experiment in which mice were exposed to different doses of radiation.

The results from the experiment are given in the table.

Description of exposure Percentage of mice getting cancer

Mice exposed to a low dose of radiation and then a high dose of radiation. 16%

Mice exposed to a high dose of radiation only. 46%

(i) Do the results from this experiment provide evidence to support ‘radiation hormesis’?

Draw a ring around your answer. NO YES

Explain the reason for your answer.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(ii) Complete the following sentence by drawing a ring around the correct word in the box.

environmental

Using animals in scientific experiments raises ethical issues.

social

(1)(Total 10 marks)

Q17.The ‘plum pudding’ model of the atom was used by scientists in the early part of the 20th century to explain atomic structure.

(a) Those scientists knew that atoms contained electrons and that the electrons had a negative charge. They also knew that an atom was electrically neutral overall.

What did this allow the scientists to deduce about the ‘pudding’ part of the atom?

........................................................................................................................

........................................................................................................................

(1)

(b) An experiment, designed to investigate the ‘plum pudding’ model, involved firing alpha particles at a thin gold foil.

If the ‘plum pudding’ model was correct, then most of the alpha particles would go straight through the gold foil. A few would be deflected, but by less than 4 °.

The results of the experiment were unexpected. Although most of the alpha particles did go straight through the gold foil, about 1 in every 8 000 was deflected by more than 90 °.

Why did this experiment lead to a new model of the atom, called the nuclear model, replacing the ‘plum pudding’ model?

........................................................................................................................

........................................................................................................................

........................................................................................................................(1)

(c) The diagram shows the paths, A, B and C, of three alpha particles. The total number of alpha particles deflected through each angle is also given.

(i) Using the nuclear model of the atom, explain the three paths, A, B and C.

A ...........................................................................................................

...............................................................................................................

B ...........................................................................................................

...............................................................................................................

C ...........................................................................................................

...............................................................................................................(3)

(ii) Using the nuclear model, the scientist E. Rutherford devised an equation to predict the proportion of alpha particles that would be deflected through various angles.

The results of the experiment were the same as the predictions made by Rutherford.

What was the importance of the experimental results and the predictions being the same?

...............................................................................................................

...............................................................................................................(1)

(Total 6 marks)

Q18. (a) The chart gives the number of protons and neutrons within the nuclei of 7 different atoms, A – G.

Which of these atoms are isotopes of the same element?

........................................................................................................................


........................................................................................................................

........................................................................................................................(2)

(b) Radium-226 is a radioactive isotope that decays into radon gas by emitting alpha particles.

The decay can be represented by the equation below.

(i) Complete the equation by writing the correct number in each of the boxes.(2)

(ii) A sample of radium-226 has a count rate of 400 counts per second.The half-life of radium-226 is 1600 years.

How long will it be before the count rate has fallen to 50 counts per second?


...............................................................................................................

...............................................................................................................

...............................................................................................................

Length of time = .............................. years(2)

(c) In 1927, a group of women who had been employed to paint watch faces with a luminous paint sued their former employer over the illnesses caused by the paint. The women had been told that the paint, which contained radium, was harmless.

The company owners and the scientists working for the company knew that radium was harmful and took precautions to protect themselves from the radiation. The women were given no protection.

What important issue did the treatment of the women by the company owners and scientists raise?


economic environmental ethical social


........................................................................................................................

........................................................................................................................(2)

(d) In the 1920s, many people, including doctors, thought that radium could be used as a treatment for a wide range of illnesses. Medical records that suggested radium could be harmful were generally ignored. When some of the women who had used the luminous paint died, their deaths were not blamed on radium.

Suggest a reason why the evidence suggesting that radium was harmful was generally ignored.

........................................................................................................................

........................................................................................................................

........................................................................................................................(1)

(Total 9 marks)

Q19.Certain types of atom emit alpha, beta or gamma radiation. The radiation is emitted from the centre of the atom.

(a) What name is given to the centre of an atom?

..................................................................(1)

(b) The sign below is used to warn people that a radiation source is being used in a laboratory.

Why is it important to warn people that a radiation source is being used?

........................................................................................................................

........................................................................................................................(1)

(c) Before using a radiation source, a teacher asked her class whether there was any way that she could reduce the amount of radiation that the source emitted. Three students each gave an answer to the teacher.

A B C

Which one of the students, A, B or C, is correct?

Write your answer in the box.

(1)

(d) The diagram shows the apparatus used by the teacher to demonstrate how one type of radiation is able to pass through lead.

One lead sheet, 2 mm thick, was placed between the source and the detector and a count rate was taken. Extra lead sheets were added. For each extra lead sheet, a new count rate was taken and recorded in the table.

Number of leadsheets

Count rate in countsper minute

1 226

2 220

3 210

4 190

5 185

Which type of radiation was the source emitting: alpha, beta or gamma?

........................................................................................................................

Give the reason for your answer.

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........................................................................................................................

........................................................................................................................(2)

(e) The diagram shows how a company detects any boxes left empty by an automatic filler.

When an empty box passes between the beta source and the detector, a buzzer sounds. A worker then removes the box from the conveyor belt.

(i) Why would this system not work if an alpha source were used instead of the beta source?

...............................................................................................................

...............................................................................................................(1)

(ii) The chart shows how the detector reading changes as boxes pass along the conveyor belt.

Which part of the chart, K, L, M or N, shows that an empty box is passing between the beta source and the detector?

..................................................................


...............................................................................................................

...............................................................................................................(2)

(Total 8 marks)

Q20.In the early part of the 20th century, scientists used the ‘plum pudding’ model to explain the structure of the atom.

Following work by Rutherford and Marsden, a new model of the atom, called the ‘nuclear’ model, was suggested.

Describe the differences between the two models of the atom.

.................................................................................................................................

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.................................................................................................................................(Total 4 marks)

Q21.The pie chart shows the sources of the background radiation and the radiation doses that the average person in the UK is exposed to in one year.Radiation dose is measured in millisieverts (mSv).

(a) (i) What is the total radiation dose that the average person in the UK receives?

...............................................................................................................

...............................................................................................................

Total radiation dose = .................................................. mSv(1)

(ii) A student looked at the pie chart and then wrote down three statements.

Which one of the following statements is a correct conclusion from this data?


In the future, more people will be exposed to a greater proportion of radon gas.

People that have never had an X-ray get 50 % of their radiation dose from radon gas.

The radiation dose from natural sources is much greater than from artificial sources.

(1)

(b) The concentration of radon gas inside a home can vary from day to day.

The table gives data for the radiation measured in homes in four different parts of the UK. The radiation was measured using two detectors, one in the living room and one in the bedroom. The measurements were taken over 3 months.

Area of the UK

Number of homes in the

area

Number of homes in the

sample

Average radiationin Bq/m3

Maximum radiationin Bq/m3

A 590 000 160 15 81

B 484 000 130 18 92

C 221 000 68 000 162 10 000

D 318 000 35 300 95 6 900

(i) Give one reason why the measurements were taken over 3 months using detectors in different rooms.

...............................................................................................................

...............................................................................................................(1)

(ii) Use information from the table to suggest why a much higher proportion of homes were sampled in areas C and D than in areas A and B.

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(Total 5 marks)

Q22.The pie chart shows the average proportions of background radiation from various sources in the UK.

(a) Three sources of background radiation are given in List A. Statements about sources of background radiation are given in List B.

Draw one line to link each source of background radiation in List A to the statement about that source given in List B.


List A List B

Are used to show broken bones.

X-rays

The radiation comes from outer space.

Cosmic rays

Comes from soil containing a radioactive isotope of potassium.

Radon gas

On average gives 50% of all background radiation.

(3)

(b) The level of background radiation from cosmic rays is not the same everywhere. For every 30 metres above sea level, the amount of background radiation increases by one unit.

The diagram shows the position of two villages, A and B, built on a hill.

How is the amount of background radiation from cosmic rays different in village Acompared to village B?

To obtain full marks, you must include a calculation in your answer.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(3)

(Total 6 marks)

Q23.The diagram represents an atom of beryllium. The three types of particle that make up the atom have been labelled.

(a) Use the labels from the diagram to complete the following statements.

Each label should be used once.

The particle with a positive charge is ......................................................................... .

The particle with the smallest mass is ....................................................................... .

The particle with no charge is .................................................................................... .(2)

(b) What is the mass number of a beryllium atom?


4 5 9 13


........................................................................................................................

........................................................................................................................(2)

(Total 4 marks)

Q24.There are many different isotopes of gold. The isotope, gold-198, is radioactive.An atom of gold-198 decays by emitting a beta particle.

(a) Complete the following sentences.

All atoms of gold have the same number of ................................................................

and the same number of .................................................................... .

The atoms from different isotopes of gold have different numbers of ........................ .

A beta particle is an .................................................................... emitted

from the .................................................................... of an atom.(3)

(b) The graph shows how the count rate from a sample of gold-198 changes with time.

Time in days

Use the graph to calculate the half-life of gold-198.

Show clearly on the graph how you obtain your answer.

........................................................................................................................

........................................................................................................................

Half-life = ............................... days(2)

(c) The diagram shows a map of a river and the river estuary.

Environmental scientists have found that water flowing into one part of the river estuary is polluted. To find where the pollution is coming from, the scientists use a radioactive isotope, gold-198.

The gold-198 is used to find where the pollution is coming from.

Explain how.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(Total 7 marks)

Q25.(a) A teacher used a Geiger-Műller (GM) tube and counter to measure the background radiation in her laboratory.

The teacher reset the counter to zero, waited one minute and then took the count reading. The teacher repeated the procedure two more times.

(i) Background radiation can be either from natural sources or from man-made sources.

Name one man-made source of background radiation.

...............................................................................................................(1)

(ii) The three readings taken by the teacher are given in the table.

Count after one minute

15

24

18

The readings given in the table are correct.

Why are the readings different?

...............................................................................................................

...............................................................................................................(1)

(b) Some scientists say they have found evidence to show that people living in areas of high natural background radiation are less likely to develop cancer than people living in similar areas with lower background radiation.

The evidence these scientists found does not definitely mean that the level of background radiation determines whether a person will develop cancer.

Suggest a reason why.

........................................................................................................................

........................................................................................................................(1)

(c) An atom of the isotope radon-222 emits an alpha particle and decays into an atom of polonium.

An alpha particle is the same as a helium nucleus. The symbol below represents an alpha particle.

(i) How many protons and how many neutrons are there in an alpha particle?

Number of protons = ...............

Number of neutrons = ...............(2)

(ii) The decay of radon-222 can be represented by the equation below.


(2)

(d) The graph shows how, in a sample of air, the number of radon-222 nuclei changes with time.

Time in days

Use the graph to find the half-life of radon-222.

Show clearly on the graph how you obtain your answer.

Half-life = .................................................. days(2)

(Total 9 marks)

Q26.The diagram shows the structure of an atom.

Not drawn to scale

(a) In 1931 scientists thought that atoms contained only protons and electrons.

Suggest what happened in 1932 to change the idea that atoms contained only protons and electrons.

........................................................................................................................

........................................................................................................................(1)

(b) The table gives information about the particles in an atom.

Complete the table by adding the names of the particles.

Particle Relative Mass Relative Charge

1 0

very small –1

1 +1

(2)(Total 3 marks)

Q27.(a) Sources of background radiation are either natural or man-made.

Which two of the sources listed in the box are natural sources of background radiation?

Draw a ring around each of your answers.

cosmic rays nuclear accidents X-rays radon gas

(2)

(b) A teacher used a Geiger-Műller (GM) tube and counter to measure the background radiation in her laboratory. The teacher reset the counter to zero, waited one minute and then took the count reading. The teacher repeated this two more times.

The three readings taken by the teacher are given in the table.

Count

17

21

19

(i) The three readings are different.

What is the most likely reason for this?

Tick ( ) one box.

The teacher did not reset the counter to zero.

Radioactive decay is a random process.

The temperature in the laboratory changed.

(1)

(ii) Calculate the mean (average) value of the three readings given in the table.

...............................................................................................................

Mean (average) value = .................................................. counts(1)

(iii) The diagram shows how the teacher used the GM tube and counter to measure the radiation emitted from a radioactive source.

The counter was reset to zero. The count after one minute was 159.

Calculate how many counts were due to the radiation from the radioactive source.

...............................................................................................................

...............................................................................................................

Counts due to the radiation from the radioactive source = ...................(1)

(iv) The teacher then put a powerful magnet between the radioactive source and the GM tube.

The counter was reset to zero. The number on the counter shows the count after one minute.

What type of radiation was being emitted from the radioactive source?


alpha beta gamma

Explain the reason for your answer.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(3)

(c) At the end of the lesson the teacher put the radioactive source back inside its storage box.

Why is the inside of the box lined with lead?

........................................................................................................................

........................................................................................................................(1)

(d) Which one of the following questions cannot be answered by scientific study?

Tick ( ) one box.

Where does background radiation come from?

What is meant by the half-life of a radioactive source?

Should radioactive waste be dumped in the oceans?

(1)(Total 10 marks)

Q28.In 2011 an earthquake caused severe damage to a nuclear power station in Japan.

The damage led to the release of large amounts of radioactive iodine-131 into the atmosphere.

(a) The table gives some information about an atom of iodine-131 .

Complete the table.

mass number 131

number of protons 53

number of neutrons

(1)

(b) Complete the sentence.

The number of protons in an atom is called the proton number or

the .............................. number.(1)

(c) An atom of iodine-131 decays into an atom of xenon (Xe) by emitting a beta particle.

(i) The decay of iodine-131 can be represented by the equation below.


(2)

(ii) A sample of rainwater contaminated with iodine-131 gives a count rate of 1200 counts per second.

Calculate how many days it will take for the count rate from the sample of rainwater to fall to 75 counts per second.

Half-life of iodine-131 = 8 days


...............................................................................................................

...............................................................................................................

.............................. days(2)

(iii) If people drink water contaminated with iodine-131, the iodine-131 builds up in the thyroid gland. This continues until the thyroid is saturated with iodine-131 and cannot absorb any more. The radiation emitted from the iodine-131 could cause cancer of the thyroid.

In Japan, people likely to be drinking water contaminated with iodine-131 were advised to take tablets containing a non-radioactive isotope of iodine.

Suggest why this advice was given.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(Total 8 marks)

Q29.(a) The names of three types of radiation are given in List A. Some properties of these three types of radiation are given in List B.

Draw one line from each type of radiation in List A to its correct property in List B.

List A

Type of radiation

List BProperty of radiation

will pass through paper but is stopped by thin metal

alpha

has the shortest range in air

beta

will not harm human cells

gamma

is very weakly ionising

(3)

(b) The radioactive isotope iodine-123 can be used by a doctor to examine the thyroid gland of a patient. The iodine, taken as a tablet, is absorbed by the thyroid gland. The gamma radiation emitted as the iodine atoms decay is detected outside the body.

The doctor uses an isotope emitting gamma radiation to examine the thyroid gland rather than an isotope emitting alpha or beta radiation.

Which one of the following gives a reason why gamma radiation is used?

Tick ( ) one box.

Gamma radiation will pass through the body.

Gamma radiation is not deflected by a magnet.

Gamma radiation has a long range in air.

(1)

(c) Iodine-123 has a half-life of 13 hours.

Use a word from the box to complete the sentence.

all half most

After 13 hours ........................................... of the iodine-123 atoms the thyroid absorbed have decayed.

(1)

(d) Iodine-123 and iodine-131 are two of the isotopes of iodine.

Draw a ring around the correct answer to complete the sentence.

electrons

The nucleus of an iodine-123 atom has the same number of neutrons as the

protons

nucleus of an iodine-131 atom.(1)

(Total 6 marks)

Q30.A teacher used the equipment shown in the diagram to measure the count rate at different distances from a radioactive source.

Metre rule

(a) Her results are shown in Table 1.

Table 1

Distance in metres Count rate in countsper minute

Corrected count rate incounts per minute

0.4 143 125

0.6 74 56

0.8 49 31

1.0 38 20

1.2 32 14

1.4 28 10

1.6 18 0

1.8 18 0

2.0 18 0

The background count rate has been used to calculate the corrected count rate.

(i) What is the value of the background count rate?

Background count rate = .............................. counts per minute(1)

(ii) What information does the corrected count rate give?

................................................................................................................

................................................................................................................(1)

(iii) The radioactive source used in the demonstration emits only one type of radiation.

The radioactive source is not an alpha emitter.

How can you tell from the data in the table?

................................................................................................................

................................................................................................................(1)

(iv) Plot a graph of corrected count rate against distance for distances between 0.4 m and 1.4 m.

Draw a line of best fit to complete the graph.

Distance in metres(3)

(v) The ‘half-distance’ is the distance a detector has to be moved away from a radioactive source for the corrected count rate to halve.

A student has the hypothesis:A radioactive source has a constant ‘half-distance’.

Table 1 has been repeated for your information.

Table 1

Distance in metres Count rate in countsper minute

Corrected count rate incounts per minute

0.4 143 125

0.6 74 56

0.8 49 31

1.0 38 20

1.2 32 14

1.4 28 10

1.6 18 0

1.8 18 0

2.0 18 0

Use Table 1 to determine if the hypothesis is correct for this radioactive source.

You should use calculations in your answer.

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................(3)

(b) A teacher places a beta source and a detector in a magnetic field.

The arrangement of the magnetic field is shown.

.......The teacher repeated the experiment with the magnetic field in a different direction.

A set of results is shown in Table 2.

Table 2

Distancebetween source

and detectorin metres

Count ratein counts per

minute without

magnetic field


minute inExperiment 1



0.8 48 48 32

(i) Describe and explain the effect of the magnetic field on the count rate detected by the detector.

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................(2)

(ii) The experiment is repeated with a different distance between the source and the detector.

Table 3 shows the repeated results.

Table 3

Distance between

source anddetectorin metres


minute without

magnetic





field

1.8 19 18 20

Explain these results.

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................(2)

(Total 13 marks)

Q31.Nuclear fission and nuclear fusion are two processes that release energy.

(a) (i) Use the correct answer from the box to complete each sentence.

Geiger counter nuclear reactor star

Nuclear fission takes place within a ........................................................ .

Nuclear fusion takes place within a ......................................................... .(2)

(ii) State one way in which the process of nuclear fusion differs from the process of nuclear fission.

................................................................................................................

................................................................................................................(1)

(b) The following nuclear equation represents the fission of uranium-235 (U-235).

Chemical symbols:

Ba - barium

Kr - krypton

(i) Use the information in the equation to describe the process of nuclear fission.

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................(4)

(ii) An isotope of barium is Ba-139.Ba-139 decays by beta decay to lanthanum-139 (La-139).

Complete the nuclear equation that represents the decay of Ba-139 to La-139.

(3)

(Total 10 marks)

Q32.Atoms contain three types of particle.

(a) Draw a ring around the correct answer to complete the sentence.

The particles in the nucleus of the atom are

electrons and neutrons.

electrons and protons.

neutrons and protons.

(1)

(b) Complete the table to show the relative charges of the atomic particles.

Particle Relative charge

Electron –1

Neutron

Proton

(2)

(c) (i) A neutral atom has no overall charge.

Explain this in terms of its particles.

................................................................................................................

................................................................................................................

................................................................................................................

................................................................................................................(2)

(ii) Complete the sentence.

An atom that loses an electron is called an ..........................................

and has an overall .................................................. charge.(2)

(d) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate.

Some substances are radioactive. They may emit alpha or beta particles.

Describe the characteristics of alpha particles and beta particles in terms of their:

• structure• penetration through air and other materials• deflection in an electric field.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................(6)

(Total 13 marks)

M1. (a) L

J

Kall 3 in correct orderallow 1 mark for 1 correct

2

(b) number of electrons = number of protonsaccept amount for number

1

(c) neutronsthis answer only

1

(d) loses / gains electron(s)1

[5]

M2. (a) proton

electron

neutronall 3 in correct orderallow 1 mark for 1 correctdo not accept letters p, e, n

2

(b) 4reason only scores if 4 is chosen

1

number of protonsaccept number of electronsaccept there are 4 protons and 4 electronsdo not accept there are 4 protons and electrons

1

(c) The atom loses an electron.1

[5]

M3. 1 mark for each correct lineIf more than 1 line has been drawn from a box in List A then all those lines are marked incorrect.

[3]

M4. (a) (i) number of protons are the sameaccept atomic number / number of electrons for number of protons

1

number of neutrons are differentaccept mass numbers are different – only if the first mark is awarded

1

(ii) an electron from the nucleusboth parts needed

1

(b) decays at the same rate as it is madeaccept decays as fast as it is madeaccept absorbed / used by plants (in CO2) at same rate as it is being made

1

(c) (i) 3500no tolerance

1

(ii) adjusted age correctly obtained from the graphaccept values between 3700–3800 inclusiveaccept their (c)(i) used correctly to obtain an adjusted age from the graph

1

adjusted age +50second mark can only be scored if first mark awardedif no working shown an answer between 3750–3850 inclusive scores both marksnote: any line or mark made on the graph counts as working out

1[7]

M5. (a) (i) L1

(ii) M1

(b) To make a smoke detector work.1

(c) 40no tolerance

1[4]

M6. (a) (i) any one from:

• food / drink

• rocks / building materials

• cosmic rays / rays from spaceaccept correctly named example

1

(ii) any one from:

• nuclear power / coal power (stations)accept nuclear waste

• nuclear accidentsaccept named accident eg Chernobyl

• nuclear weapons testingaccept named medical procedure which involves a radioactive sourceaccept radiotherapynuclear activity / radiation is insufficientdo not accept CT scans

1

(iii) different number of / fewer protonsaccept does not have 86 protonsaccept only has 84 protons

ordifferent atomic number

do not accept bottom number differentreference to mass number negates this mark

1

(b) 168accept 169 if clear, correct method is shownallow 1 mark for a correct dose ratio involving the spineeg 2:140 etcor ratio of days to dose is 1.2or ratio of dose to days is 0.83

2

(c) (i) Group A

GroupB

J M O K L N

all correctany order within each group

1

(ii) similar (number) / same (number) / large (number)accept the same specific number in each group eg threereference to other factors such as age is neutral

1

(iii) how many people in each group developed cancera clear comparison is required

1

(iv)there are no marks for Yes or No themark is for the reason

Yesthe benefit of having the scan is greater than the riskorthe risk is (very) small (compared to the chance from natural causes)

accept the risk is much greater from natural causes

Nono additional risk is acceptable

1[9]

M7. (a) electron(s)1

(b) 3rd box ticked

The model cannot explain the results from a new experiment1

(c) all three correct

Particle

Proton

Electron

Neutron

allow 1 mark for 1 correct2

[4]

M8.three lines correctallow 1 mark for each correct lineif more than 1 line is drawn from a box in List A, mark each line incorrect

[3]

M9. (a) beta1

alpha: would not pass through (the aluminium / foil)1

gamma: no change in count rate when thickness changesmust be a connection between detection / count rate / passing through and change in thickness

1

(b) foil thickness increases then decreases (then back to normal / correct thickness)a description of count rate changes is insufficient

1

gap between rollers decreases, then increases (then back to correct size)orpressure from rollers increases then decreases

accept tightness for pressureanswers may link change in thickness and gap width for full credit ie:

foil thickness increases so gap between rollers decreases (1)foil thickness decreases so gap between rollers increases (1)

1

(c) 56 (years)accept any value between 55-57 inclusiveallow 1 mark for correct calculation of mass remaining as 1.5 (micrograms)allow 1 mark for a mass of 4.5 micrograms plus correct use of graph with an answer of 12maximum of 1 compensation mark can be awarded

2[7]

M10. (a) 1 mark for each correct line

if more than 1 line is drawn from any box in List A, none of those lines gain any credit

3

(b) (i) (the detector) reading had gone down‘it’ equals detector readingaccept the reading in the table is the smallestaccept 101 is (much) lower than other readings / a specific value eg 150do not accept this answer if it indicates the readings are the thickness

1

more beta (particles / radiation) is being absorbed / stoppedaccept radiation for beta particles / radiationaccept fewer particles being detected

1

(ii) six years1

(iii) alpha would not penetrate the cardboardaccept the basic property – alpha (particles) cannot pass through paper / cardaccept alpha (particles) are less penetrating (than beta)range in air is neutral

1[7]

M11. (a) (i) (total) number of protons plus neutronsaccept number of nucleonsaccept amount for numberdo not accept number of particles in the nucleus

1

(ii) number of neutrons decreases by one1

number of protons increases by oneaccept for both marks a neutron changes into a proton

1

(b) (i) 1

correct order only1

(ii) the number of protons determines the elementaccept atomic number for number of protons

1

alpha and beta decay produce different changes to the number of protonsthere must be a comparison between alpha and beta which is more than a description of alpha and beta decay alone

oralpha and beta decay produce different atomic numbers

ignore correct reference to mass number1

[7]

M12. (a) (i) half / 50 %1

(ii) Measure the radon gas level in more homes in this area1

(b) (i) 861

(ii) 2221

[4]

M13. (a) cobalt-(60)1

gamma (radiation) will pass through food / packagingthis can score if technetium chosen

1

long half-life so level of radiation (fairly) constant for (a number) of yearsthis can score if strontium / caesium is chosenaccept long half-life so source does not need frequent replacementaccept answers in terms of why alpha and beta cannot be usedgamma kills bacteria is insufficient

1

(b) (i) people may link the use of radiation with illness / canceraccept (they think) food becomes radioactiveaccept (they think) it is harmful to them‘it’ refers to irradiated food

1

(ii) not biased / influenced (by government views)1

(iii) any two from:

• data refers only to (cooked) chicken

• data may not generalise to other foods

• the content of some vitamins increases when food / chicken is irradiated

• no vitamins are (completely) destroyed

• (only) two vitamins decrease (but not significantly)accept irradiated chicken / food contains a higher level of vitamins

marks are for the explanation only2

(iv) so can choose to eat / not eat that (particular) foodaccept irradiated food may cause health problems (for some people)accept people may have ethical issues(over eating irradiated food)

1

(c) (i) electronfrom nucleus / neutron

both parts required1

(ii) 90 yearsallow 1 mark for showing 3 half-lives

2[11]

M14. (a) (i) 200 to 50accept either order

1

(ii) 5.3accept values between 5.2 and 5.4 inclusive

1

(iii) 5.3accept values between 5.2 and 5.4 inclusive

ortheir (a)(ii)

1

(b) (i) Make the conveyor belt move more slowly1

(ii) lead1

(c) Exposure increased the content of some types of vitamin.1

[6]

M15. (a) (i) 1.25 (mSv)1

(ii) any two from:

• (frequent) flyingaccept stated occupation that involves flying

• living at altitude

• living in areas with high radon concentrationsaccept a specific area, eg Cornwall

• living in a building made from granite (blocks)

• having more than the average number of X-raysorhaving a CT scanaccept more medical treatments

• working in a nuclear power stationaccept any suggestion that could reasonably increase the level from a specific source

2

(b) (i) to be able to see the effect of exposure (to radon gas)oras a control

accept to compare (the effect of) exposure (with no exposure)1

(ii) increased levels of exposure increases the risk (of developing cancer)accept exposure (to radon gas) increases the risk

1

smoking increases the (harmful) effect of radonanswers that simply reproduce statistics are insufficient

1

(c) LNT model – risk increases with increasing radiation (dose) levelaccept in (direct) proportionaccept low doses increase the risk

1

Radiation hormesis - low radiation (dose) levels reduce the risk1

(d) two valid points made – examples:

• animals have no choice and so should not be used

• should not make animals suffer

• better to experiment on animals than humans

• experiments lead to a better understanding / new knowledge

• experiments may lead to health improvement / cures for humansresults for animals may not apply to humans is insufficient

2[10]

M16. (a) (i) on average, cosmic rays produce less background radiation than rocks.1

having no X-rays reduces a person's radiation dose.1

(ii) 4allow 1 mark for 350 / 4allow 1 mark for an answer 3.5

2

(b) (i) (risk) increases1

(ii) Creason only scores if C chosen

1

shows a lower risk for low doses (than for zero exposure)accept risk reduces when you go from low to moderate (doses)

1

(c) (i) no mark for YES or NO, marks are for the explanation

YES

fewer mice exposed first to a low dose1

get cancer (than those only exposed to a high dose)only scores if first marking point scores

NO

the results are for mice (1)

and may not be applicable to people (1)1

(ii) ethical1

[10]

M17. (a) has an equal amount of positive chargeaccept pudding/it is positive

1

(b) (experimental) results could not be explained using ‘plum pudding’ modelor(experimental) results did not support plum pudding model

accept (experimental) results disproved plum pudding model1

(c) (i) A – most of atom is empty spaceormost of atom concentrated at the centre1

B – nucleus is positive (so repels alpha particles)accept nucleus has the same charge as alpha

1

C – nucleus is very smallaccept nucleus is positive if not scored for B

ornucleus is a concentrated mass

accept nucleus has a very concentrated charge1

(ii) (if predictions correct, this) supports the new modelanswers should be in terms of the nuclear modelaccept supports his/new/nuclear theoryaccept proves for supportsaccept shows predictions/ Rutherford was correct

1[6]

M18. (a) B E Gall 3 required and no otherany order

1

same number of / 88 protons (and different numbers of neutrons)same number of electrons is insufficient

1

(b) (i) 2221

861

(ii) 4800allow 1 mark for obtaining 3 half-lives

2

(c) ethical1

deceived / lied to (about safety of working conditions)accept (women) not warned of the dangersgiven no protection is insufficient

orvalue own / scientists' lives more than womenordid not treat women humanely

1

(d) accept any sensible suggestionegtoo many interests in continued use of radium

evidence may cause public unrestdo not accept not enough evidence

doctors not want to be blamed for illnesses (caused by radium)accept doctors not wanting to be sued (for harm caused by using radium)

doctors thought (possible) benefits outweighed (possible) risksdo not accept did not know radium could be harmfulbelieve radium could treat illnesses is insufficient

1[9]

M19. (a) nucleusdo not accept core / centre / middle

1

(b) radiation damages our cellsaccept radiation is dangerous / poisonous / harmful / toxicaccept radiation can cause cancer / kills cells / change DNA / cause mutations / harm healthaccept so precautions can be takenaccept so they know they may be exposed to / harmed by radiation it refers to radiation (source)to stop people being harmed is insufficient

1

(c) C1

(d) gamma1

gamma will pass through the leadreason only scores if gamma chosen

oralpha and beta will not pass through lead

accept correct symbols for alpha, beta and gamma1

(e) (i) range of alpha too shortaccept alpha would not reach detector

oralpha absorbed whether box is full or empty

accept alpha (always) absorbed by box / cardaccept alpha will not pass through the box / cardalphas cannot pass through objects / solids is insufficientalpha not strong enough is insufficient

1

(ii) Mreason only scores if M chosen

1

less radiation / beta (particles) absorbedaccept more radiation / beta particles pass through

ormore radiation absorbed by full boxes

accept reading is higher1

[8]

M20.any two pairs from:to gain credit it must be clear which model is being describeddo not accept simple descriptions of the diagram without comparison

• nuclear model mass is concentrated at the centre / nucleus (1)accept the nuclear model has a nucleus / the plum pudding model does not have a nucleus for 1 mark

plum pudding model mass is evenly distributed (1)

• nuclear model positive charge occupies only a small part of the atom (1)

plum pudding model positive charge spread throughout the atom (1)

• nuclear model electrons orbit some distance from the centre (1)accept electrons in shells / orbits provided a valid comparison is made with the plum pudding model

plum pudding electrons embedded in the (mass) of positive (charge) (1)do not accept electrons at edge of plum pudding

• nuclear model the atom mainly empty space (1)

plum pudding model is a ‘solid’ mass (1)[4]

M21.(a) (i) 2.51

(ii) The radiation dose from natural sources is much greater than from artificial sources

1

(b) (i) any one from:

• different concentrations in different rooms

• to average out daily fluctuationsaccept to find an averageaccept to make the result (more) reliable / validdo not accept to make more accurate on its own

1

(ii) average level (much) higher (in C and D)accept converse

1

some homes have very high level (in C and D)accept maximum level in A and B is low

1

or

maximum level in some homes (in C and D) is very highaccept higher radiation levels (in C and D) for 1 mark

[5]

M22.(a) 1 mark for each correct line

if more than 1 line has been drawn from a box in List A then all those lines are marked incorrect

3

(b) higher in village B1

by 6 unitsallow 1 mark for correctly obtaining a height difference of 180 (m) / 4 times higher – this refers to height not radiation levelsaccept for 3 marks in village A it is 2 units (extra) and in village B it is 8 units (extra) allow 1 mark for a correct radiation calculation based on incorrect height readings

2[6]

M23.(a) protonall 3 in correct order

electronallow 1 mark for 1 correct do not

neutronaccept letters p, e, n

2

(b) 9reason only scores if 9 is chosen

1

number of neutrons and protons1

[4]

M24.(a) protons, electronsboth required, either order

1

neutrons

1

electron, nucleusboth required, this order

1

(b) 2.7 (days)allow 1 mark for showing correct use of the graph

2

(c) put source into water at one point on bankaccept the idea of testing different parts of the river bank at different times

1

see if radiation is detected in polluted areaaccept idea of tracing

or

put source into water at three points on bank (1) see if radiation is detected downstream of factory or farmland or sewage treatment works (1)

1[7]

M25.(a) (i) any one from:

• nuclear power (stations)accept nuclear waste accept coal power stations

• nuclear weapons (testing)accept nuclear bombs / fallout

• nuclear accidentsaccept named accident, eg Chernobyl or Fukushimaaccept named medical procedure which involves a radioactive source accept radiotherapy accept X-rays accept specific industrial examples that involve a radioactive sourcenuclear activity / radiation is insufficientsmoke detectors is insufficient

1

(ii) (radioactive decay) is a random processaccept an answer in terms of background / radiation varies (from one point in time to another)

1

(b) any one from:

• (maybe) other factors involvedaccept a named ‘sensible’ factor, eg smoking

• evidence may not be validaccept not enough data

• may not have (a complete) understanding of the process (involved)1

(c) (i) 21

21

(ii) 218correct order only

1

841

(d) 3.8 (days)allow 1 mark for showing correct method using the graph provided no subsequent stepscorrect answers obtained using numbers other than 800 and 400 gain 2 marks provided the method is shown

2[9]

M26.(a) neutron discovered1

(b) neutronall 3 in correct order

electronallow 1 mark for 1 correct

proton2

[3]

M27.(a) cosmic rays1

radon gas1

(b) (i) Radioactive decay is a random process1

(ii) 191

(iii) 140accept 159 – their (b)(i) correctly calculated

1

(iv) gamma1

the count stayed the same1

or

gamma does not have a chargeaccept gamma is an electromagnetic wave

(so) gamma is not deflected / affected by the magnetic fieldaccept magnet for magnetic fielddo not accept is not attracted to the magnetlast two marks may be scored for an answer in terms of why it cannot be alpha or betaonly answer simply in terms of general properties of gamma are insufficient

1

(c) lead absorbs (some of the) radiationaccept radiation cannot pass through (the lead)

or

less radiation emitted into the (storage) room1

(d) Should radioactive waste be dumped in the oceans1

[10]

M28.(a) 781

(b) atomic1

(c) (i) 131correct order only

1

541

(ii) 32 (days)allow 1 mark for showing 4 half-lives provided no subsequent step

2

(iii) limits amount of iodine-131 / radioactive iodine that can be absorbedaccept increases level of non-radioactive iodine in thyroiddo not accept cancels out iodine-131

1

so reducing risk of cancer (of the thyroid)accept stops risk of cancer (of the thyroid)

1[8]

M29.(a) 3 lines correct

allow 1 mark for each correct lineif more than one line is drawn from any type of radiation box then all of those lines are wrong

3

(b) Gamma radiation will pass through the body1

(c) half1

(d) protons1

[6]

M30.(a) (i) 181

(ii) the count rate for the source1

(iii) the alpha radiation would not cover such a distance1

(iv) plots correct to within ½ small squareallow 1 mark for 4 correct points plotted

2

correct curve through points as judged by eye1

(v) two attempts at finding ‘half-distance’ using the table20 to 10 cpm d = 0.4 m125 to 56 cpm d = 0.2 m31 to 14 cpm d = 0.4 mallow 1 mark for one attempted comparison

2

obeyed or not obeyeddependent on previous two marks

1

(b) (i) there is no effect on the count rate in experiment 1 because the field is parallelor beta particles are not deflected or there is no force

1

count rate is reduced in experiment 2 because field is perpendicular or beta particles are deflected or there is a force

1

(ii) only background radiation (as beta do not travel as far)1

slightly different values show the random nature of radioactive decay1

[13]

M31.(a) (i) nuclear reactor1

star1

(ii) nuclei are joined (not split)accept converse in reference to nuclear fissiondo not accept atoms are joined

1

(b) (i) any four from:

• neutron• (neutron) absorbed by U (nucleus)

ignore atomdo not accept reactsdo not accept added to

• forms a larger nucleus• (this larger nucleus is) unstable• (larger nucleus) splits into two (smaller) nuclei / into Ba and Kr• releasing three neutrons and energy

accept fast-moving for energy4

(ii) 56 (Ba)1

57 (La)if proton number of Ba is incorrect allow 1 mark if that of La is 1 greater

1

accept e for β

scores 3 marks

1[10]

M32.(a) neutrons and protons1

(b) 01

(+)11

(c) (i) total positive charge = total negative chargeaccept protons and electrons have an equal opposite charge

1

(because) no of protons = no of electrons1

(ii) ion1

positive1

(d) Marks awarded for this answer will be determined by the quality of communication as well as the standard of the scientific response. Examiners should apply a best-fit approach to the marking.

0 marksNo relevant content

Level 1 (1 – 2 marks)There is a basic description of at least one of the particles in terms of its characteristics.

Level 2 (3 – 4 marks)There is a clear description of the characteristics of both particlesora full description of either alpha or beta particles in terms of their characteristics.

Level 3 (5 – 6 marks)There is a clear and detailed description of both alpha and beta particles in terms of their characteristics.

examples of the physics points made in the response:

structure

• alpha particle consists of a helium nucleus• alpha particle consists of 2 protons and 2 neutrons• a beta particle is an electron• a beta particle comes from the nucleus

penetration

• alpha particles are very poorly penetrating• alpha particles can penetrate a few cm in air• alpha particles are absorbed by skin• alpha particles are absorbed by thin paper• beta particles can penetrate several metres of air• beta particles can pass through thin metal plate / foil• beta particles can travel further than alpha particles in air• beta particles can travel further than alpha particles in materials eg metals

deflection

• alpha particles and beta particles are deflected in opposite directions in an electric field

• beta particles are deflected more than alpha particles• alpha particles have a greater charge than beta particles but beta particles

have much less massorbeta particles have a greater specific charge than alpha particles

6[13]

E1. (a) Nearly three quarters of candidates scored both marks and a further fifth of candidates scored one mark.

(b) Nearly two fifths of the candidates gained this mark, with‘amount’ being an alternative to‘number’. Many of the incorrect answers were of the type‘electrons cancel out the protons’,‘the negatives cancel out the positives’, and neutrons were often mentioned instead of either protons or electrons.

(c) Over half of candidates gained this mark.

(d) Just under two thirds of candidates gained this mark by mentioning either the losing or gaining of electron(s). Many candidates made reference to the outside shell becoming complete as a result; some went too far and were confused with the sharing of electrons as in covalent bonding.A few candidates made the mistake of‘electrons are lost so leaving a negative charge’ and as in part (b), some candidates talked about neutrons or protons being lost/gained instead

of electrons.

E2. (a) Nearly three quarters of candidates gained both marks.

(b) Just over a third of the candidates achieved the maximum of two marks for this part question. It was noticeable that there were rather more responses in terms of the candidates believing that the number of electrons defined the atomic number, (a response accepted by the examiners), rather than the correct definition based on the number of protons present. Just over half of the candidates were unable to identify the correct atomic number.

(c) Just under three quarters of candidates gained this mark.

E3. Just under two thirds of candidates gained all three marks.

E4. (a) (i) About half of the candidates gained both of the available marks. Many of the wrong answers indicated that candidates knew there was a connection to numbers of sub-atomic particles, but got them the wrong way round.

(ii) Less than a third of candidates correctly identified a beta particle as an electron from the nucleus. Whilst a large number of candidates knew that the beta particle was an electron, the majority thought it was emitted from the electron shells.

(b) Nearly four fifths of answers failed to score this mark. Some candidates realised that the carbon-14 was decaying, but failed to equate this to the rate of production. Others referred to the carbon-14 being‘used up’ but did not elaborate on the way in which this was happening.

(c) (i) Fewer than half of candidates answered this correctly. Whilst some candidates found difficulty in understanding the question, others used the graph in the correct way, but mis-read one or other of the axes.

(ii) More than a tenth of candidates did not attempt this question, either because they ran out of time or because they found it too difficult. Under half of candidates gained at least one mark, for obtaining an adjusted age from the carbon dating age; a

common mistake was to use the axes the wrong way round. Only about half of those who scored the first mark subsequently added 50 years to obtain their final answer.

E5. (a) (i) The majority of candidates correctly identified L as being the electron.

(ii) Only a quarter of the candidates knew that an alpha particle is made up of two protons and two neutrons, and therefore was represented by M on the diagram.

(b) Most of the better candidates realised that one application of alpha radiation is to make a smoke detector work. About half of all candidates gained the mark for this question.

(c) The great majority of candidates correctly read the graph and arrived at the answer of 40.

E6. (a) (i) Surprisingly only three-fifths of candidates answered this question correctly. A significant number of candidates incorrectly suggested various electromagnetic waves such as infra red or ultraviolet, with quite a few candidates naming microwaves.

(ii) Again surprisingly few candidates (less than two-fifths) gave a correct answer to this part question. The most common incorrect answers were radiation types: ‘alpha’, ’beta’, ’gamma’. Candidates should be made aware that a CT head scan uses X-rays, and as such this was not an acceptable answer. As in part (a)(i) too many candidates named parts of the electromagnetic spectrum.

(iii) Almost half of the candidates gave the correct answer to this question. A common mistake was to discuss the change to the mass number (or neutron number) in addition to the change in the proton number, leading to confusion over which aspect caused the formation of a new element. For some candidates, it appeared as if they were simply describing alpha-emission (ie ‘X has 2 fewer protons and two fewer neutrons’) which is the answer to a question they were asked in a previous paper but is not the answer to this question.

(b) Over three-quarters of candidates scored both marks for this question. Many of the candidates not scoring both marks lost the opportunity to gain one compensation mark by ignoring the instruction ’Show how you work out your answer’.

(c) (i) Virtually all candidates scored this mark.

(ii) The vast majority of candidates answered correctly. A fairly common error was the answer: ’even’ taken to mean an even number: 2, 4, 6 in each group, but not necessarily the same number in each group. A few candidates had not read the question (which was about the number of people) and made suggestions about the

people instead.

(iii) Only about a quarter of candidates responded correctly. Most candidates who answered incorrectly, answered with a variation of the following, ’See if the group who were X-rayed got cancer’. The question asked ’what data was compared?’ so there needed to be a reference to both groups so candidates needed to focus on this with their answer. Common incorrect vague answers included reference to ‘medical history’.

(iv) The vast majority of candidates gave correct answers; most incorrect answers involved the candidate circling ’Yes’ and then providing an answer that would be valid if the ’No’ option had been circled. Candidates should be made aware that they need to provide more information than is given in the question, for example: ’There is a 1 in 10,000 chance of getting cancer from a CT head scan’ is worth zero, but ’There is only a 1 in 10,000 chance of getting cancer from a CT head scan and so the risk is small’ is worth a mark. The candidate needs to interpret and emphasise details contained in the stimulus material.

E7. (a) About one0third of candidates could identify the particle as an electron.

(b) Just over three-quarters of candidates chose the correct statement.

(c) Almost three-fifths of candidates named all three particles correctly. Only just over a tenth of candidates failed to name any of the particles correctly.

E8. This question demonstrated the need for candidates to learn basic facts. Just over a quarter of candidates scored zero and a further two-fifths scored only one mark. There was a large variety of incorrect links, one of the most common being a chain reaction happening in a star.

E9. (a) In this part question candidates often gave an incomplete answer, saying that the gamma radiation would go through the aluminium, rather than qualifying this with ‘whatever thickness the aluminium is’. Common insufficient responses were to state the general properties of each type of radiation without relating it to the specific situation shown. Only a tenth of candidates gained all three marks.

(b) The principle behind this question, ie that a drop in count rate signified an increase in thickness and vice versa, seemed to be quite well understood. Unfortunately, this was not always backed up by sufficiently detailed answers and many candidates only referred to the initial increase in thickness without mentioning the subsequent decrease. Similarly, the response of the system was not always referred to or described in terms of the changing roller pressure or gap width. Nearly three fifths of candidates failed to score any marks.

(c) Of the candidates who appeared to understand how to tackle this question, a variety of responses was seen, including incorrect calculation of the remaining 25 % of 6 micrograms, inaccurate drawing of lines on the graph and misreading of the scales on the graph.

E10. (a) Few candidates were able to score all three marks on this question, but the majority were able to score at least one. The most common mistake was to say that gamma radiation is very strongly ionising.

(b) (i) Most candidates were able to score one mark for realising that the detector reading had fallen significantly at that time.Few however were able to gain the second mark for explaining the cause of this. Some simply said that this was because the cardboard was thicker, but this information was given to candidates in the question. Some candidates thought that the reading at 8.45 was an anomalous result rather than understanding that it was a true result and that something had happened to cause it.

(ii) Very few candidates correctly chose six years as a suitable half life; the most common answer was six months.

(iii) The better candidates realised that alpha radiation would not be able to penetrate cardboard. Many other candidates simply gave general properties of alpha radiation without relating it to this particular situation. There were also many candidates who thought that alpha radiation would simply be too weak.

E11. (a) (i) Most students knew the answer but some failed to score the mark as they just wrote ‘protons and neutrons’. Other incorrect answers concerned the ‘weight of an atom’ or an answer of ‘212’, the mass number given in the question.

(ii) About one fifth of the students scored both marks and a few more scored 1 mark. Many students explained that as an electron was emitted and as it had negligible mass the overall mass would not be affected. However this did not answer the set question. Worryingly, far too many of those students thought that the emitted electron had come from the shells rather than from the nucleus.

(b) (i) Over three quarters of students scored both marks. However a number of students wrote acorrect answer only to change to a wrong one. A large proportion of those students who got it wrong insisted on adding 4 and 2 to get 216 and 85, others divided by 4 and 2.

(ii) The final item on the paper might be expected to help to identify the A* students, and this succeeded; only a few students scored both marks but most of those answers were beautifully written. Many students didn’t make it clear that it is the proton number that defines the element and many students hedged their bets by stating that it couldn’t be the same element as both the atomic number and the mass number had changed in alpha emission.

E12. (a) (i) This was correctly answered by nearly all students.

(ii) Only just over half of the students scored this mark, many students thought it would be best to ignore the data.

(b) (i) Just over half of the students scored this mark.

(ii) Just over two thirds of students realised the need to add the two numbers given and so scored this mark.

E13. (a) A few students scored all three marks for this question, with nearly three quarters scoring zero. Many students gave the impression, both here and in (b)(i), that the food would become radioactive, therefore a short half-life would be beneficial so that the radiation would have decreased to an insignificant level by the time the food was purchased. The most common incorrect response was Technetium-99, for this reason.

(b) (i) Whilst a large number of students scored this mark, many students indicated, as stated previously, that the food would be radioactive.

(ii) The majority of students realised that independent scientific committees would remove the risk of bias. Sometimes this idea is not very well expressed, for instance quite a few answers indicated that the ‘government would lie’ to further their own aims.

(iii) Around one third of the students were able to state two valid points from the data given, with a further half of students stating one point. The most common responses were that the content of three vitamins increased on irradiation, and that of two vitamins decreased.

(iv) Over three quarters of students answered this correctly.

(c) (i) Whilst many students knew that a beta particle is an electron, and many knew that it is emitted from the nucleus of an atom, less than half the students were able to state both parts of the answer correctly.

(ii) Around one third of students answered this correctly. Whilst a number of students were able to show the count rate halving in stages, many stated the answer as ‘3’ instead of realising that it was 3 half-lives. Some students also halved the half-life in stages, and some halved the 137 of caesium-137.

E14. (a) (i) This question was well done with two thirds of students scoring the mark. A common incorrect response was to give a range of ‘0 to 200’.

(ii) This was poorly done with only a third of students being able to obtain the correct time from the graph.

(iii) Most students did not realise that they had been led to the value of the half-life in part (a)(ii).Consequently many students began to calculate the half-life value again, mostly with little success. Only a quarter of students scored this mark.

(b) (i) Only just over half the students scored this mark.

(ii) Just over three fifths of students were able to correctly identify ‘lead’.

(c) Most students were able to identify a correct conclusion to score this mark.

E15. (a) (i) It is perhaps surprising that only two-thirds of students scored this mark. Many students failed to read the question carefully and gave an answer of 2.5, the total dose received.

(ii) Most students scored one mark, usually for a response associated with flying, but only half of which went on to score both marks. Most errors were due to lack of detail, for example, working in a power station rather than a nuclear power station, or simply living in an area with a high background level without specifying the source of that increased level.

(b) (i) Almost two-thirds of students scored this mark. The most popular correct response was the idea of a control. The most common error was stating ‘to compare smokers to non-smokers’ with no reference to radon gas.

(ii) Just over half the students scored one mark for making the simple link between exposure to radon gas and the increased risk of cancer. Less than a third of students made a correct link to smoking increasing the harmful effect of the radon gas

exposure.

(c) This question was generally well answered with just over half of students scoring both marks a further quarter of students scoring one mark. Those students scoring no marks often simply described the shape of the graph line rather than identifying the differences between the two models.

(d) Just over half of students scored both marks often producing a well written balanced view. A further third of students scored one mark.

E16. (a) (i) Nearly half of students scored both marks. Most of the remaining students achieved one mark.

(ii) Just fewer than half of students correctly calculated that four X-rays just exceeded the yearly average radiation dose from the table. The most common error was to use the total average radiation dose received each year and produce a response of twenty five.

(b) (i) Most students were able to identify correctly the relationship between the risk of getting cancer and the radiation dose levels.

(ii) About two-thirds of students identified graph C as the one which identified the effect of radiation hormesis, but only half of those students gave a correct reason for their choice. Many responses were not comparative regarding the reduced risk of cancer that zero exposure to radiation achieved and an exposure to low radiation doses.

(c) (i) Although a majority of the students realised that the experimental evidence supported the effect known as radiation hormesis, the explanations given were often too vague to achieve credit.

(ii) Just over half of students identified the issue as being ‘ethical’.

E17. (a) Nearly 60% of students scored this mark, usually for the accepted answer ‘it is positive’. Failure to earn the mark was usually due to the mention of a nucleus or protons.

(b) This was very poorly answered and correct answers were often poorly worded. Too many students simply wrote how the “new model” was different from the “plum pudding” model, not why the evidence failed to support the old model.

(c) (i) The majority of answers referred to the observations and made no attempt to explain the paths in terms of the nuclear model. Quite a number of students tried to explain the paths as those of alpha, beta and gamma. Just over 76% of students scored

zero. Only approximately 6% of students scored 2 or 3 marks.

Path A: Many answers referred to “passing straight through the empty space”, suggesting students had the idea of what was shown by the results but were unable to be precise enough.

Path B: Some students gained the mark for the nucleus being positive. However some answers talked loosely about repulsion but failed to explain why this should happen. Some students referred to interaction with electrons.

C: Those students scoring a mark here generally did so for the nucleus being positive; if not scored in B. A very few students scored the mark for “nucleus very small”, or for “very concentrated charge”

(ii) Many students scored this mark for simply stating that Rutherford was correct or had been proved to be correct. Those students that failed to score this mark usually wrote in general terms and often about reliability, accuracy and validity.

E18. (a) This question was quite well answered.

(b) (i) Just over 33% of students gained at least one mark.

(ii) Whilst many students had some idea that they were supposed to halve a number, a large number of them halved either the half-life or the nucleon number of 226. Another common mistake was to double the time as the count rate halved. Just over 55% of students scored zero.

(c) Whilst about half of the students correctly chose ‘ethical’, few were able to give a reason, often just quoting the information given in the question that the women were given no protection.

(d) Despite the question referring to ‘the evidence suggesting that radium was harmful’, a large number of answers stated that there was ‘no evidence’.

E19. (a) The majority of students gained this mark.

(b) This question was well answered. Most students could give a correct consequence of exposure to radiation. Students should be told that answers such as ‘radiation affects you’ are insufficiently precise to gain credit.

(c) Most students scored this mark.

(d) Many students correctly identified ‘gamma’ as the radiation in question, but fewer students were able to give an unambiguous reason for their choice. Answers were either vague, for example ‘gamma is strong’ or simply listed general properties of the three radiations without linking them to this example. Other students stated that ‘no radiation will pass through lead’ despite evidence to the contrary. However, some good, clear answers were seen.

(e) (i) Too many answers were couched in terms of the general properties of alpha radiation and did not address the particular scenario in this question. Only a minority of students answered correctly that the material of the box would absorb alpha radiation, making the presence or absence of powder an irrelevance. Very few references were seen to the ‘range’ of alpha radiation and again many vague answers discussing the strength or weakness of the radiation were given.

(ii) Nearly every student correctly identified M as the empty box. However, only a handful of students then went on to give a correct reason for their choice. Many thought that the reading for M was lower than the others (it’s higher) and others simply appeared to pick M because it was different to K, L or N. The fact that beta radiation would be absorbed less by an empty box was rarely seen.

E20.A very small number of the students scored all 4 marks, and a majority of the students scored zero. A major problem was again a lack of clear description or a failure to read the question carefully which resulted in a description of one or the other models without reference to differences.

E21.(a) (i) The majority of the students gained this mark. Errors included omitting the 0.01 mSv for ‘other’ or giving an answer of 0.25 rather than 2.5 mSv.

(ii) Nearly three quarters of the students gained this mark.

(b) (i) Nearly two thirds of the students gained this mark.

(ii) Nearly half of the students failed to gain a mark for this item. The most common error was to give answers in terms of the number of houses in each area. A smaller number gained one mark for giving reference to either the average higher level or the high maximum level.

E22.(a) Nearly three quarters of the students gained all three marks. The most common error was to link radon gas to ‘Comes from soil containing a radioactive isotope of potassium’.

(b) Nearly half of the students gave a clearly expressed answer to gain all three marks.

E23.(a) Most students were able to score both marks. Errors were equally distributed between the three particles.

(b) Just over half of the students could give both the correct number and reason for their choice.

E24.(a) About two-thirds of students were able to gain at least one of the three marks, but few

scored all three marks.

(b) Just under half of the students gained both marks, with a small number gaining one mark for correctly marking the graph, but misreading the value from the time axis.

(c) A small number of responses gained at least one of the marks, even less scoring both marks. There was little indication that students understood the concept of a radioactive tracer, at least in the given context.

E25.(a) (i) Surprisingly only just over half of students gained this mark, with the popular answers being ‘nuclear power stations’ or ‘nuclear weapons testing’. ‘X-Rays’ was also a common response. The common incorrect responses were smoke detectors and vague answers referring to medical uses without being specific. A significant number of students failed to see that ‘man-made sources’ was in bold and responded with ‘cosmic rays’ and ‘rocks’.

(ii) Several students gave the correct response in terms of background radiation varying but relatively few gave the answer in terms of decay being a random process. Common incorrect answers referred to the teacher moving the experiment around the lab to cause the differences or to other radioactive sources being present at the times of the three readings, including the introduction of radioactive materials into the room and the presence of different food being present when the readings were taken. Many did use ‘vary’ or ‘changes’ but too many gave responses showing a complete lack of understanding of this process.

(b) The most common correct response was ‘other factors’. When other factors were mentioned, it was usually smoking. Several students gave answers referring to the hereditary aspect of cancer. Very few answers talked about the validity of the evidence, or the sample size.

(c) The majority of the students gained both marks.

(d) Almost two thirds of the students gave the correct response of 3.8 days, with a few giving the answer as a fraction and one or two converting 0.8 days into hours and minutes. Nearly all correct answers used the counts of 800 and 400 to determine the half-life. A few misread the x axis scale and then answered 3.4 days and a few, after drawing correct lines then put down an incorrect answer. Common errors included believing the “222” of radon was important and so a line was drawn across from a count of 222 to give a half-life near 7 days.

E26.(a) This was very poorly answered. Few students were able to link the diagram of the atom and the question to suggest that the neutrons shown in the diagram were discovered in 1932. Many students gave answers in terms of technology improvements and were under the misconception that it became possible to see the subatomic parts of an atom.

(b) This part was better answered with over half of students gaining both marks.

E27.(a) Just under two thirds of students correctly identified the two sources. X-rays was a commonly given incorrect answer.

(b) (i) Just under two thirds of students gained this mark.

(ii) Most students were able to correctly calculate the mean value.

(iii) Only the more able students understood that the background count needed to be subtracted from 159. Many students gave the answer as 159 having ignored the background value.

(iv) Just over half of students recognised that gamma was being emitted from the source, but few could give a valid explanation for this. A significant number of students simply wrote about the relative penetrating power of alpha, beta and gamma, with many of these students thinking that the gamma rays could pass through the actual magnets. The more able students explained that gamma rays were not deflected by the magnetic field, but only a few stated that the count had stayed the same.

(c) Nearly two thirds of the students gained this mark. Most of these gave an answer in terms of lead absorbing radiation. A common error was to say that the lead stopped the source from getting out.

(d) Just under half of the students identified the correct answer.

E28.(a) A majority of students scored this mark.

(b) Again, a majority of students scored this mark.

(c) (i) Over half of students scored zero, the most common error being an attempt to change mass and proton numbers in accordance with alpha decay. Students who got the proton number correct almost always scored full marks. The most common mistake made with the mass number was subtracting 1 rather than adding 1.

(ii) Under half of students correctly answered this for both marks. A minority of students scored one mark for correctly identifying four half-lives sufficiently well to gain credit. The most common mistake amongst students scoring one mark was to neglect to multiply 4 by 8, leaving 4 as the answer. Of the students who failed to score any marks 1200/75 to give 16 days was one common misconception, another was in counting five half-lives, i.e. 1200 as 1 half-life, 600 as 2 half-lives etc. resulting in an answer of 40. A disappointing number of students could not multiply 4 × 8 correctly, giving answers of 24 or 36.

(iii) Only 10% of students scored both marks for this question. Some students scored one mark for correctly stating that the tablets inhibit the absorption of I-131 but not stating the link to a reduced chance of developing cancer. Some students scored one mark for indicating that the tablets did reduce the chance of developing cancer but with incorrect reasoning. Two common misconceptions were that the tablet acted like a vaccination to prepare the body to deal with the radioactive iodine using anti-bodies, or that the non-radioactive iodine would in some way neutralise the radioactivity of I-131.

E29.(a) Surprisingly nearly one third of students scored zero.

(b) The vast majority of students were able to identify the correct reason for using gamma radiation.

(c) Over half of the students scored this mark. The most popular incorrect answer was ‘all’.

(d) Very poorly answered with over half of the students failing to score the mark.

E30.(a) (i) Nearly all students were able to determine the value of background count from a table listing values of count rate and corrected count rate.

(ii) Only half of the students stated that corrected count is the count rate due to the source.

(iii) Well over half of the students knew that the data given in the table was not related to an alpha source. Some stated that it could not be an alpha source because the readings of count rate were not high enough. Others backed up their correct answers with realistic ranges for alpha particles.

(iv) The standard of graph plotting was very high and more than two thirds of students scored full marks for accurate plotting and drawing a curve through the points.

(v) Students were introduced to the idea of half-distance and were asked to state whether a constant value of half distance could be seen from the data given in the table. Some very good answers were seen with over a third of students scoring all three marks.

There was conflicting evidence in the table and students were expected to make a judgement on the data that they used. Many students were stuck with the idea of half-life and used this term throughout.

A common error was ‘if the count rate did not halve when the distance doubled, then the hypothesis was invalid’. Here the doubling of distance is irrelevant; it is the change in distance that matters. Many students used the change in distance of 0.4 m resulting in the count rate halving from 20 to 10 as the basis of a successful answer.

Many students gave up immediately because 56 was not half of 125.

(b) (i) This question scored very poorly, with very few students able to describe the effect of a magnetic field on a beam of beta particles. Many thought that the magnetic field blocked the particles or that the particles went off in the direction of the field or were reflected backwards by the field. There were many loose statements such as ‘when the magnetic field travels towards the detector’.

(ii) Hardly any students realised that the readings were due to background count. They often gave long explanations as to why the three readings were different including that in experiment 1 the magnetic field repels the particles back towards the source.

E31.(a) (i) Nearly all students knew that nuclear fission takes place within a reactor and that nuclear fusion takes place within a star.

(ii) Less than half of the students could state a way in which fusion differs from fission. Many statements referred to atoms or elements instead of nuclei.

(b) (i) A nuclear equation representing fission was given and students were asked to use the information in the equation to describe the process of fission.

This was well answered, with just under half of the students gaining all four marks. Many statements relating to fission were seen which ignored the given equation. For example ‘two or three neutrons are released’ when the equation clearly showed three.

(ii) Only a quarter of students could complete a nuclear equation depicting beta minus emission by adding subscripts for atomic number and a correct symbol for a beta particle.

Many students are unclear concerning the symbol, subscript and superscript for a beta particle.

· web view(b) exposure to radon gas can cause lung cancer.a recent study has compared the risk of...

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