Paper 1 - Radioactivity

Question 1

what is an isotope

Answer 1

a different form of an atom of the same element with the same number of protons but different number of neutrons, therefore having a different mass number

Question 2

what are the three types of ionising radiation

Answer 2

alpha, beta, gamma

Question 3

why is an atom unstable sometimes

Answer 3

isotopes are sometimes unstable because they have too many neutrons

Question 4

when would an atom stop being radioactive

Answer 4

when it has formed into a stable new element

Question 5

what is background radiation and where does it come form

Answer 5

radiation that is always present everywhere, coming from...
cosmic rays from space
living things
buildings/air/food/soil/rock
human activity eg nukes or nuclear waste

Question 6

what is ionisation

Answer 6

when radiation emits a particle which knocks into a neutral atom and knocks off electrons from it, making it an ion

Question 7

what is the relationship between penetrating power and ionising power

Answer 7

the more penetrating, the less ionising

Question 8

features of alpha particles

Answer 8

they are helium nuclei
mass number 4, atomic number 2
2 protons and 2 neutrons
very heavy and slow
strongly ionising
electrically charged - therefore are deflected by electric and magnetic fields

Question 9

features of beta particles

Answer 9

they are electrons
created when a neutron turns into a proton and an electron
relatively fast and small - moderately ionising
negatively charged so are deflected by electric and magnetic fields

Question 10

features of gamma rays

Answer 10

no mass - just energy
emitted only after the emission of a beta or alpha particle - never alone
weakly ionising
penetrate very well
no charge, no deflection
emitted when a nucleus has excess energy

Question 11

effect of alpha particle emission on nucleus

Answer 11

mass number decreases by 4

atomic number decreases by 2

Question 12

effect of beta particle emission on nucleus

Answer 12

mass number stays the same

atomic number increases by 1

Question 13

effect of gamma emission on nucleus

Answer 13

everything stays the same

Question 14

how to balance nuclear equations

Answer 14

the total atomic and mass number has to be the same on both sides of the equation

Question 15

what is half-life

Answer 15

the time taken for half of the radioactive atoms now present to decay

Question 16

how to find half life

Answer 16

divide total time by how many half lives in that time

Question 17

how to find half life on graph

Answer 17

halve vertical axis and time corresponding time

Question 18

penetrating power of alpha particles

Answer 18

blocked by paper, skin and even a few cm of air

Question 19

penetrating power of beta particles

Answer 19

blocked by thin metal

Question 20

penetrating power of gamma radiation

Answer 20

thick lead or thick concrete

Question 21

uses of alpha radiation and how it works

Answer 21

fire alarms
Some smoke detectors use a piece of radioactive Americium, and α emitter. The α particles are sent into two chambers — one is a reference one, the other is open to air. Since the air is ionized in the process, a voltage difference between the two cells is measured. If smoke enters the chamber open to air, it affects the voltage difference between the smoke filled and reference chambers, and if this difference reaches a threshold, the alarm goes off.

Question 22

uses of beta radiation and how it works

Answer 22

thickness gauges
beta radiation directed at piece of paper or metal being thinned
detector on the other side
detector senses changes in radiation, which causes it to adjust thickness
beta is used as it can penetrate paper/metal when thin, but not too well when thick

Question 23

uses of gamma radiation and how it works

Answer 23

medical tracers

• radioactive source which emits gamma or beta is injected into body
• detected externally, allowing doctor to monitor progress
• checks if organs are working properly
• must have short half life so it is high enough to be detected but also doesn’t stay in body too long

tracers to check pipe leaks
-same concept, can detect where leak are in pipes

Question 24

how is radiation used to treat cancer

Answer 24

radiotherapy which kills tumor

Question 25

radiation for sterilisation

Answer 25

medical equipment / food - kills microbes

Question 26

what is irradiation

Answer 26

exposure to radiation

Question 27

what is contamination

Answer 27

when radioactive atoms get onto or into an object

Question 28

what is nuclear fission

Answer 28

the splitting of a nucleus

Question 29

what is nuclear fusion

Answer 29

the joining of two nuclei

Question 30

describe the process of nuclear fission and chain reactions

Answer 30

slow moving neutron absorbed by a uranium -235 nucleus, causing nucleus to split which releases more neutrons which will collide with more nuclei and so on

Question 31

what is formed when uranium is split (excluding neutrons)

Answer 31

two daughter nuclei form which are usually radioactive - this is nuclear waste

Question 32

how is energy generated from nuclear fission

Answer 32

co2 pumped round the reactor which transfers the energy by heating to the water , which becomes steam and spins a turbine

Question 33

how is overheating in a reactor prevented

Answer 33

boron control rods which absorb neutrons

Question 34

what is the purpose of the moderator and what is it

Answer 34

graphite, water or heavy water which slows down neutrons so they can be absorbed by uranium nuclei

Question 35

what happens in fusion

Answer 35

two lighter nuclei collide and fuse together to form a larger, heavier nucleus
the larger heavier nucleus doesn’t have as much mass as the two small ones combined as a lot is lost as it is converted to energy

Question 36

problems of fusion

Answer 36

requires too high temperature and pressure in order to overcome electrostatic repulsion between nuclei that cannot be recreated on earth (yet)