p6 - radioactivity (from PMT)

Question 1

give two ways that an atom’s electron arrangement can be changed

Answer 1

1.absorbing electromagnetic radiation
2.emitting electromagnetic radiation

Question 2

explain how an atom’s electron arrangement changes when it absorbs EM radiation

Answer 2

-electrons move further away from the nucleus
-they move to a higher energy level

Question 3

explain how an atom’s electron arrangement changes when it emits EM radiation

Answer 3

-electrons move closer to the nucleus
-they move to a lower energy level

Question 4

what do all forms of the same element have in common

Answer 4

the number of protons

Question 5

why do unstable nuclei give out radiation

Answer 5

-unstable nuclei undergo decay to become more stable
-as they release radiation their stability increases

Question 6

what is the name of the process in which an unstable nucleus gives out radiation to become more stable?

Answer 6

radioactive decay

Question 7

state four types of nuclear radiation

Answer 7

1.alpha particles
2.beta particles
3.gamma rays
4.neutrons

Question 8

what is an alpha particle made of?

Answer 8

-two protons + two neutrons (same as a helium nucleus)

Question 9

what will stop beta radiation from passing through a point?

Answer 9

-a thin sheet of aluminium
-several metres of air

Question 10

define a beta particle

Answer 10

a fast-moving, high-energy electron that is emitted from the nucleus of an atom

Question 11

define an alpha particle

Answer 11

a positively charged nuclear particle that consists of two protons and two neutrons

Question 12

what will stop gamma radiation from passing through a point?

Answer 12

-a few metres of concrete
-several cm of lead

Question 13

describe the nature of radioactive decay

Answer 13

-random
-which nuclei decays and when is determined only by chance
-it is impossible to predict which nuclei will decay and when

Question 14

define the half-life of a radioactive isotope

Answer 14

-the time it takes for the number of unstable nuclei in a substance to halve
-the time it takes for the count rate from a sample to fall to half its initial level

Question 15

define radioactive contamination

Answer 15

the presence of unwanted radioactive nuclei on other materials

Question 16

define irradiation

Answer 16

-the process of exposing a material to nuclear radiation
-the material does not become radioactive

Question 17

give 3 practical applications of radioactive materials

Answer 17

-medical tracers
-radiotherapy
-smoke alarms

Question 18

what kind of radiation is used in smoke detectors

Answer 18

alpha radiation

Question 19

how do smoke alarms work

Answer 19

alpha radiation is emitted into the air, reaching a detector and completing the circuit. if smoke is present, it blocks alpha radiation so it does not reach the detector and the circuit is broken, causing an alarm to sound

Question 20

give a use of beta emitters

Answer 20

thickness monitoring of paper

Question 21

how does thickness monitoring work

Answer 21

a source and receiver are placed on either side of the sheet. if there is a drop or rise in the number of particles detected, the thickness has changed and needs adjusting

Question 22

why are isotopes with long half-lives particularly harmful?

Answer 22

-they remain radioactive for much longer periods of time
-they must be stored in specific ways to avoid humans and the environment from being exposed to radiation for too long

Question 23

state two uses of nuclear radiation in the field of medicine

Answer 23

1.examining of internal organs
2.controlling and destroying unwanted tissue

Question 23

how is radiation used in sterilisation

Answer 23

gamma emitters are used to kill bacteria/parasites on equipment

Question 24

what kind of radiation is used for radiotherapy?

Answer 24

gamma radiation

Question 25

explain the process of radiotherapy

Answer 25

-gamma emitters direct gamma rays onto specific areas with cancerous cells
-the cells absorb the radiation and die

Question 26

what are the risks of ionising radiation to people

Answer 26

it can damage living cells, causing them to die or mutate and become cancerous

Question 27

define nuclear fusion

Answer 27

a process in which two light nuclei merge to form a single heavier nucleus, releasing energy in the process

Question 28

name two isotopes of hydrogen which are commonly used in nuclear fusion

Answer 28

deuterium and tritium

Question 29

which releases more energy, nuclear fission or nuclear fusion?

Answer 29

nuclear fission

Question 30

explain the difficulty of generating energy through nuclear fusion

Answer 30

fusion requires very high temperatures which in itself requires large quantities of energy and also requires casing which can withstand then

Question 31

what is nuclear fission

Answer 31

the splitting of large, unstable nuclei to form smaller more stable nuclei (+ the emission of spare neutrons)

Question 32

what usually needs to happen to induce fission?

Answer 32

-the unstable nuclei must absorb a neutron
-spontaneous fission (where no neutron absorption occurs) is rare

Question 33

alongside two smaller nuclei, what else is emitted in a fission reaction

Answer 33

-2 or 3 neutrons
-gamma rays
-energy

Question 34

what takes place during a chain reaction in a nuclear reactor?

Answer 34

-an unstable nucleus absorbs a neutron
-the nucleus undergoes fission and releases 2 or 3 further neutrons
-these induce more fission, which results in a chain reaction