WSC Unit 1 Yr 11 Physics Chap 1 Test Answers; 2011

  1. U and U have the same atomic number but different mass numbers.
  1. Protons = 92
    Neutrons = 238 – 92 = 146
  1. In the nucleus, the strong nuclear force of attraction is much greater than the push of the protons repelling each other, and therefore the nucleus remains intact.
  1. Nuclear fission is the splitting apart of a large nucleus to form two smaller, more stable nuclei.

a: / 35
b: / 3
  1. 57 + a = 92 \ a = 35

236 = 148 + 85 + b \ b = 3

  1. Fast neutrons are released by the fission of U atoms. [omitted]
(a)  Control rods control the rate at which energy is produced in the reactor core.
(b)  To do this, the control rods absorb neutrons.
  1. To keep the temperature constant throughout the reactor.
  2. To transfer heat energy from the reactor core to the heat exchanger.
  1. Either a series of equations: [marked very flexibly esp. as the Np step(s) could not have been known by students]
    U + n à U
    U à Np + b
    Np à Pu + b;
    or a written answer:
    Uranium-238 absorbs a neutron and becomes uranium-239. This unstable isotope releases a b particle and becomes neptunium-239. Another b particle is released and the nucleus becomes plutonium-239.
  1. Nuclear fusion is the process where two small nuclei are joined to make a larger nucleus. For example, two hydrogen nuclei fusing together to form a helium nucleus (or any other similar fusion equation).

Part B Answers

  1. b radiation is identical to electrons.
  1. radiation occurs when a neutron turns into a proton (that remains in the nucleus) and an electron (that is ejected from the nucleus).
  1. The atomic number increases by one. The mass number remains constant.
  1. g, b, a
  1. a, b, g
  1. An a particle is identical to a helium nucleus.
  1. Protons = atomic number = 86
    Neutrons = mass number – atomic number = 212 – 86 = 126
  1. Atomic number = 86 – 2 = 84
    Mass number = 212 – 4 = 208
(a)  One half-life has passed; therefore, half of the original mass remains:
64 g remains.
(b)  Two half-lives have passed; therefore, one quarter of the original mass remains:
32 g remains.
  1. The absorbed dose is the amount of energy absorbed by each kilogram of the tissue being irradiated.
  1. The dose equivalent is a means of comparing the biological effects of different types of radiation. The dose equivalent = absorbed dose ´ quality factor.
  1. Absorbed dose 6.9 × 10–4 Gy
  1. Dose equivalent = absorbed dose × quality factor = 6.9 × 10–4 × 1 = 6.9 × 10–4 Sv or 0.69 mSv
  1. Dose equivalent = absorbed dose × quality factor = 6.9 × 10–4 × 12 = 8.3 × 10–3 Sv or 8.3 mSv