1 How is the mass number calculated 2

1) How is the mass number calculated (2). Answer Protons + Neutrons

2) What is the atomic number equal to. (2) Answer Proton number or electron number

3) How is the Neutron number calculated (2). Mass number - proton number = neutron number

4) What is an isotope (2). Ans: Atoms with same number of protons and different number of neutrons.

5) Which one of these is an Isotope of Element a) 18 X 8 or b) 16 X 9. Ans: a) 18 X 8 16 X 8.

6) What happens to unstable radioactive isotopes (2). Ans: • Decay • and give out ionising radiation

7) Name three types of radiation that are produced when an unstable isotope decays (3) Answer • alpha • beta • gamma

8) How do alpha, beta and gamma cause ionisation (3) Answer a) Alpha particle which have a (large positive charge) pull negatively charged particles out of orbit (attraction). b) Beta particles (which are negative charged) repel electrons out of orbit c) Gamma rays transfer energy to electrons and the electrons receive the energy and break free from orbit of the atom.

9) Describe the properties of alpha particles (3). Answer They are • Strongly ionising • Don’t penetrate much because they are stopped by a few cm of air or paper • Heavy, slow moving positive charge. • Contain 2 protons and 2 neutrons (equivalent to a Helium nucleus)

10) Describe the properties of beta particles (3). Answer They are • Moderately ionising (less then alpha) • They are moderately penetrating (stopped by thin sheet of aluminium). • Fast and small • Equivalent to a high-speed (highenergy) electron

11) Describe the properties of gamma radiation (3). Answer They are • Weakly ionising • They are very penetrating (only stopped by thick lead or very thick concrete). • Part of the electromagnetic spectrum. • Travel at the speed of light

12) What is nuclear fission ? Answer It is the splitting up of uranium nuclei to release huge amounts of energy.

13) What is the process by which nuclear fission produces huge amounts of energy? Answer Chain reaction

14) How is a chain reaction initiated. Answer. Absorption of neutron by a radioactive nucleus such as uranium.

15) What is produced when a chain reaction is initiated. (3) Answer • 2 daughter nuclei (Krypton and Barium) • 3 neutrons • A huge amount of energy

16) Describe what happens in a chain reaction in a nuclear reactor (6) Answer • Neutron fired at an isotope of uranium-235. • Neutron absorbed by uranium 235 Nuclues. • Nucleus becomes unstable and splits into two daughter nuclei (which are themselves very radioactive), • A lot of energy is released, and 3 more neutrons. • The neutrons are absorbed by other Uranium-235, causing them to split and so on - chain reaction.

17) Explain how a nuclear power station produces energy (6). Answer • A high-energy neutron collides with a uranium nucleus in the fuel rod and produce 2 daughter nuclei (Krypton and Barium), 3 neutrons and a huge amount of energy. • Control rods capture excess neutrons and reduce the total number of fission reactions to prevent an uncontrollable chain reaction. • Thermal energy is transferred to the heat exchanger, • Which converts water into steam; • Which turns a turbine, • Which turns the generator to produce electricity.

18) What is nuclear fusion ? Answer It is the joining of two light small nuclei (e. g Hydrogen) to create a larger nucleus; in order to produce energy.

19) Give some advantages of fusion reactions Answer • Produces a lot more energy compared with fission. • No radioactive waste-only helium produced. • Plenty of hydrogen around.

20) What are the difficulties with fusion? (3) Answer. • Fusion only happens at very high temperatures and/or pressures • Because a lot of energy is needed to bring two highly positive charges together (they would normally repel). • Reactors are very expensive to make as they need to withstand very high temperatures.

21) What are the similarities between fission and fusion? (4) Answer • Energy is released. • Involve nuclei. • Involve particles colliding. • Can cause explosions.

22) What are the key differences between fission and fusion (6). Answer • Fission involves splitting of nuclei; fusion involves joining/fusing of nuclei • Fission creates smaller nuclei; fusion creates a larger one • Fission creates radioactive waste; fusion creates no radioactive waste, just He nuclei • Fusion produces much more energy • Fission involves chain reaction. • Fusion requires extremely high temperatures and pressures

23) What is cold fusion? Answer Fusion at normal conditions not requiring the high temperatures.

24) Why is cold fusion not an accepted theory. (2) Answer It has not been validated by other scientist; (peer reviewed). Other scientist could not repeat their experiment to validate it. It was deemed unreliable.

25) Describe some of the risks of working at nuclear power plants and link with the precautions that need to be taken (6) Answer • (R) Fuel rods have high temperature when removed from reactor. (P) Protective clothing and handling systems should be used. • (R) Damage to rods during transport. (P) Use of canister to carry fuel rods. • (R) Prolonged exposure to radiation cause {tissue / cell} damage and {mutation / damage to DNA. (P) Minimise their exposure to the ionising radiation. • (R) Increased risk due to long term exposure to raised background levels of radiation. (P) monitoring of background levels of radiation