Radiation and the Universe B+ questions Name: Q. The diagram below shows a method of controlling the thickness of paper produced at a paper mill. A radioactive source which emits beta radiation is placed on one side of the paper and a radiation detector is placed on the other. (a) How will the amount of radiation reaching the detector change as the paper gets thicker?...... () (b) Explain, as fully as you can: (i) why a radioactive source which emits alpha (α) radiation could not be used for this application. () (ii) why a radioactive source which emits gamma (γ) radiation could not be used for this application. () iii) why a radioactive source which emits beta (β) radiation can be used for Page
this application. Q2. (a) The diagram shows what can happen when the nucleus of a uranium atom absorbs a neutron. (Total 5 marks) (i) What name is given to the process shown in the diagram? () (ii) Explain how this process could lead to a chain reaction. You may wish to add further detail to the diagram to help your answer. Page 2
(iii) How does the mass number of an atom change when its nucleus absorbs a neutron? () Total 4 marks Q3. (a) As part of its life cycle, a star changes from being a protostar to a main sequence star. Explain the difference between a protostar and a main sequence star. (b) The early Universe contained only atoms of hydrogen. The Universe now contains atoms of over one hundred different elements. Explain how the different elements now contained in the Universe were formed. (3) (Total 5 marks) Page 3
Q4. (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? Give a reason for your answer. (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. Page 4
(ii) A sample of radium-226 has a count rate of 400 counts per second. The half-life of radium-226 is 600 years. How long will it be before the count rate has fallen to 50 counts per second? Show clearly how you work out your answer.......... Length of time =... years (c) In 927, 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? Draw a ring around your answer. economic environmental ethical social Give a reason for your answer. (d) In the 920s, 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. () (Total 9 marks) Page 5
Q5. In 986, a nuclear reactor exploded in a power station at Chernobyl in the Ukraine. (a) The table gives information about some of the radioactive substances released into the air by the explosion. Radioactive substance Half-life Type of radiation emitted Iodine-3 8 days beta and gamma Caesium-34 2 years beta Caesium-37 30 years beta (i) How is the structure of a caesium-34 atom different from the structure of a caesium-37 atom?.. () (ii) What is a beta particle and from which part of an atom is a beta particle emitted?.... () (iii) Once a radioactive substance is dissolved in rainwater, it can enter the food chain. Following the Chernobyl explosion, some milk supplies were found to be radioactive. If one litre of milk contaminated with iodine-3 gives a count rate of 400 counts/second, how long will it take for the count rate to fall to 25 counts/second? Show clearly how you work out your answer....... Time taken =... days Page 6
(iv) After 20 years, the caesium-37 emitted into the atmosphere is a more serious problem than the iodine-3. Explain why........... (Total marks) Page 7
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Radiation and the Universe B+ questionsmarkscheme M. (a) decrease for mark (b) (i) none would go through paper for mark (ii) all would go through paper for mark (iii) only some absorbed/amount absorbed depends on thickness of paper for mark each 2 [5] M2. (a) (i) (nuclear) fission accept fision providing clearly not fusion (ii) (released) neutrons are absorbed by further (uranium) nuclei accept hit nuclei for absorbed / hit do not accept atom for nuclei more neutrons are released (when new nuclei split) accept for both marks a correctly drawn diagram (iii) increases by or goes up to 236 Page 9
M3. (a) a protostar is at a lower temperature or a protostar does not emit radiation /energy as (nuclear) fusion reactions have not started accept heat or light for energy (b) by (nuclear) fusion accept nuclei fuse (together) nuclear fusion and fission negates this mark of hydrogen to helium elements heavier than iron are formed in a supernova accept a specific example e.g. heavier elements such as gold are formed in a supernova accept heavier elements (up to iron) formed in red giant/red super giant reference to burning (hydrogen) negates the first 2 marks [5] Page 0
M4. (a) B E G all 3 required and no other any order same number of / 88 protons (and different numbers of neutrons) same number of electrons is insufficient (b) (i) 222 86 (ii) 4800 allow mark for obtaining 3 half-lives 2 (c) ethical deceived / lied to (about safety of working conditions) accept (women) not warned of the dangers given no protection is insufficient or value own / scientists' lives more than womenor did not treat women humanely (d) accept any sensible suggestion eg too many interests in continued use of radium evidence may cause public unrest do 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) risks do not accept did not know radium could be harmful believe radium could treat illnesses is insufficient Page
[9] M5. (a) (i) 3 fewer neutrons accept fewer neutrons accept different number of neutrons do not accept different number of electrons (ii) electron from the nucleus both points needed (iii) 32 (days) allow mark for clearly obtaining 4 half-lives 2 (iv) has a much longer half-life accept converse answers in terms of iodine-3 accept it has not reached one half-life yet little decay happened / still in the atmosphere accept it is still decaying [6] Page 2