P2 Revision Booklet

More Radiation

Medium (Grade C)

Q1.          (a)     Nuclear fission is used in nuclear power stations to generate electricity. Nuclear fusion happens naturally in stars.
(i)      Explain briefly the difference between nuclear fission and nuclear fusion.
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(2)

(ii)     What is released during both nuclear fission and nuclear fusion?
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(1)

(b)     Plutonium-239 is used as a fuel in some nuclear reactors.
(i)      Name another substance used as a fuel in some nuclear reactors.
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(1)

(ii)     There are many isotopes of plutonium.
What do the nuclei of different plutonium isotopes have in common?
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(1)
(Total 5 marks)
 Q2.          The process of nuclear fusion results in the release of energy.
(a)     (i)     Describe the process of nuclear fusion.
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(2)

(ii)     Where does nuclear fusion happen naturally?
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(1)

(b)     For many years, scientists have tried to produce a controlled nuclear fusion reaction that lasts long enough to be useful. However, the experimental fusion reactors use more energy than they produce.
(i)      From the information given, suggest one reason why nuclear fusion reactors are not used to produce energy in a nuclear power station.
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(1)

(ii)     Suggest one reason why scientists continue to try to develop a practical nuclear fusion reactor.
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(1)

(c)     In 1989, two scientists claimed in a daily newspaper that they had produced nuclear fusion reactions in normal laboratory conditions. The process became known as ‘cold fusion’. Other scientists thought that the evidence produced to support ‘cold fusion’was unreliable.
(i)      Suggest one reason why other scientists thought that the evidence to support ‘cold fusion’ was unreliable.
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(1)

(ii)     In 2007, the results of a new ‘cold fusion’ research project were published in a respected scientific journal. This journal includes scientists such as Albert Einstein amongst its past authors.
Suggest why people may be more likely to believe an article published in a respected scientific journal than one published in a daily newspaper.
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(1)
(Total 7 marks)
 Q3.          Radon is a radioactive element. The graph shows how the number of radon atoms in a sample of air changes with time.

(i)      How long did it take the number of radon atoms in the sample of air to fall from 1000 to 500?
Time = ................................................... seconds
(1)

(ii)      How long is the half-life of radon?
Half-life = ............................................. seconds
(1)

(iii)     Complete this sentence by crossing out the two lines in the box that are wrong.

 
As a radioactive material gets older, it emits	less
a constant level of
more	 
radiation per second. 	

(1)
(Total 3 marks)
 Q4.          Some students measure the level of radiation from a radioactive source during the same lesson each week over a period of six weeks.
          Here are the results. (They have been corrected for background radiation.)
 
Time (weeks)	start	1	2	3	4	5	6	
Level of radiation (average counts per minute)	66	44	34	29	16	12	8	

(a)     Using the graph paper below, display these results in the most appropriate way.

(5)

(b)     What overall pattern is there in the students’ results?
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(3)
(Total 8 marks)
 Q5.          Some rocks contain the radioactive isotope uranium–235 (235U).
          235U has a half-life of 700 million years and, as it decays, lead–207 (207Pb) is eventually formed.
(a)     Draw a decay curve for 235U on the graph below.

(4)

(b)     Samples of an igneous rock gave an average ratio of 70 atoms of 235U to 30 atoms of 207 Pb.
          Use the decay curve you have drawn to estimate the age of the igneous rock.
Answer ..................................... million years.
(1)

(c)     A sandstone rock which lies above the igneous rock contains traces of uranium-235 and of lead-207.
          Why might it be unsatisfactory to use this uranium for dating the sandstone?
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(2)
(Total 7 marks)
 More radiation-Mark scheme

M1.         (a)      (i)     (nuclear) fission is the splitting of a (large atomic) nucleus
do not accept particle/atom for nucleus
1

(nuclear) fusion is the joining of (two atomic) nuclei (to form a larger one)
do not accept particles/atoms for nuclei
1

(ii)     energy 
accept heat/radiation/nuclear energy
accept gamma (radiation)
do not accept neutrons/neutrinos
1

(b)     (i)      uranium (–235) 
accept U (–235)
ignore any numbers given with uranium
accept thorium
accept MOX (mixed oxide)
do not accept hydrogen
1

(ii)     (same) number of protons 
accept (same) atomic number
accept (same) positive charge
ignore reference to number of electrons
1
[5]
 M2.         (a)      (i)     (two) nuclei (of light elements) join
accept hydrogen atoms for nuclei
1

forming a larger / heavier nucleus / one
accept comparative term equivalent to larger
accept forms a helium (nucleus / atom) this mark only scores if fusion is in terms of hydrogen atoms
1

(ii)     stars 
accept a named star
e.g. the Sun
accept nebula
mention of planets negates answer
1

(b)     (i)     any one from:
•        (currently) only experimental
•        reaction does not last long enough
•        use more energy than they produce
allow difficult to control
do not allow inefficient on its own
1

(ii)     any one from:
•        will give another source of energy
•        unlimited fuel supplies / energy
accept unlimited hydrogen
•        would not produce any radioactive waste
accept less radioactive waste
accept nuclear for radioactive
do not accept toxic waste
•        want to show that it can be done
accept any sensible suggestion
do not accept answers only in terms of fossil fuels or carbon dioxide
1

(c)     (i)     any one from:
•        repeating did not produce the same results / data
accept could not be repeated
accept has not been repeated
•        experiments were not / may not be reproducible
•        data / experiments were not valid
do not accept answers in terms of scientists being biased
1

(ii)     any one from:
•        cannot trust journalists
bias is insufficient on its own
•        newspaper journalist may not have a science background
•        newspaper may publish what people want to read
•        newspaper may simplify ideas
•        people believe / trust the scientists writing the journal
•        people have heard of the scientists writing in the journal
•        scientists writing in the journal are famous
•        journal only publishes the work of respected / famous scientists
•        data is checked by other scientists before published in the journal
accept any sensible suggestion, these are examples they do not constitute a full list
1
[7]
M3.          (i)      50 ± 5
1
(ii)      50 ± 5
accept their (b)(i)
1
(iii)     less
accept any way of indicating the correct answer
1
[3]
 M4.          (a)     at least 6 points correctly plotted
gains 1 mark
          (to better than half a square) but all points correctly plotted
gains 2 marks
2
          any line graph related to plotted points; 
point (3,29) discounted;
best fit smooth curve
each for 1 mark
3

(b)     radiation decreases with time
gains 1 mark
          but decreases quickly at first then more slowly
gains 2 marks
          but idea that  it (about) halves every 2 weeks or half-life is (about) 2 weeks
gains 3 marks
3
[8]
 M5.          (a)     one relevant point correctly plotted
gains 1 mark
          but two relevant points correctly plotted
gains 2 marks
          but three relevant points correctly plotted
gains 3 marks
          curved line drawn accurately through the points
for 1 further mark
4

(b)     age of igneous rock = 400 ± 100 million years
1

(c)     sandstone is a sedimentary rock
for 1 mark
          there is likely to be some lead–207 present
or from the rocks from which the sandstone was formed
for 1 mark
          (allow 207 Pb may not have come from this 235U)
2
[7]