Radioactivity and Particles

Question 1

what are isotopes

Answer 1

atoms with the same number of protons but a different number of neutrons

Question 2

what happens if the nuclei of an isoptope is unstable

Answer 2

if the nucleus has an imbalance of protons or neutrons it is more likley to decay into several smaller nuclei until stable nuclei are obtained

Question 3

when does radiactive decay happen

Answer 3

spontaniously
it is UNaffected by physical conditions like temperature or any sort of chemical bonding

Question 4

what happens when the nucleus decays

Answer 4

it will emmit one or more types of radiation
- alpha, beta or gamma

Question 5

examples of background radiation

Answer 5

substances on earth (air, food, soil..)
radiation from space
living things
human activity

Question 6

how does nuclear radiation cause ionisation

Answer 6

nuclear radiation causes ionisation bu bashing into atoms and knocking electrons off of them
the atoms are turned into ions

Question 7

what is the machine for detecting ionising radiation

Answer 7

geiger-muller dectector
photographic film

Question 8

what are alpha particles made of
and they qualities

Answer 8

2 protons
2 neutrons
big, heavy, slow moving

Question 9

how do alpha aprticles work

Answer 9

they are strongly ionising meaning they bash into a lot of atoms and knock electrons off them which creates a lot of ions

Question 10

what does emmiting alpha particles cause

Answer 10

decrease the atomic number of the nucleus by 2 and the mass number by 4

Question 11

what are beta particles
and qualities

Answer 11

an electrons which as been emmited from the nucleus of an atom when a neutron turns into a proton and electron
fast and small
moderately ionising

Question 12

what happens when a beta particle is emmited

Answer 12

the number of proton in the nucleus increases by 1 the atomic number increases by 1
BUT the mass number stays the same

Question 13

what are gamma rays

Answer 13

no mass and just energy
they penetrate a long way into materials
no charge
weakly ionising
pass through rather than colliding with atoms

Question 14

what effect does gamma ray emission have

Answer 14

it has no effect on the atomic or mass number of the isotope

Question 15

order of more ionising

Answer 15

alpha are more than beta
beta are more than gamma

Question 16

rule for nulcear equations

Answer 16

the overall charge and mass has to be the same before and after a nucelar reaction has happened

Question 17

how can alpha be blocked

Answer 17

paper, skin or a few cm of air

Question 18

how can beta particle be blocked

Answer 18

a few cm of metal

Question 19

how can gamma rays be blocked

Answer 19

thick lead or very thick concreate

Question 20

set up for how to investiage penetration of radiation

Answer 20

Question 21

how to find the penetration of radiation

Answer 21

remove the source and find the background radiation
place the source and measure the count rate
then place different materials between the source and detector

Question 22

how to know if the material can block the penetration of radiation

Answer 22

of the count rate remains the same when the material is insterted, then the radiation can penetrate the material

if it drops by a large amount then the radiation is being absorbed and blocked by the material

if it drops to zero after the background count if subtracted, the radiation is being completely absorbed

Question 23

safety for radioactive sources

Answer 23

use in a lead lined box when not in used
on picked up using long-handled tongs or forceps
do not point at anyone

Question 24

definition of half life

Answer 24

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

Question 25

short vs long half lifes

Answer 25

short half life means the activity falls quickly and lots of nuclei decay quickly

long half life means the activity falls slowly because the atoms dont decay for a long time

Question 26

steps for finding half life
the activity of a radioactive isotope is 640Bq
Two hours later it has fallen to 40 Bq
Find the half life of the sample

Answer 26

initial count - 640
after one half life (/2) - 320
after two half lives (/2) - 160
after three half lives - 80
after 4 half lives - 40
it takes 4 half lives for the activity to fall from 640 to 40
this means 2 hours represents 4 half lives so the half life is (2 hours / 4) = 30 minutes

Question 27

how can beta and gamma radiation be used

Answer 27

in medical tracers
eg
a source which emmits beta or gamma can be injected or sqalloed and it will penetrate the body tissues to be detected externeally but a source
doctors can use this to make sure organs are working as they should

Question 28

how can gamma rays be used

Answer 28

for sterilising food equipment
it will skill a microbes and it doesnt involve high temperatures so things such as plastic instruments or fresh fruit can be sterilised without being damaged

Question 29

how can ionising radiation cause damage to cells and tissues

Answer 29

alpha radiation collides with molecules in your cells and this can either damage or destroy the molecules

low dose will cause minor damage and cause mutations which is cancer

high doses kill cells completely and it causes radiation sickness

Question 30

irridation

Answer 30

object near a radioactive source causes irridation (they are exposed to it)
it DOES NOT make it radioactive

Question 31

contamination

Answer 31

if unwanted radioactive atoms get onto or into an object the object will be contamination
these atoms may decay causing you harm

Question 32

what is nulcear fission

Answer 32

the splitting of an atom which releases energy
it can be spontaneous

Question 33

what happens in nuclear fission

Answer 33

a slow moving neutron is absorbed by a uranium 235 nucleus the nucleus can split
each time this happens it spits out a small number of neutrons which may go hit other ones causing them to split and so on
it creates daughter nuclei

Question 34

energy with nuclear fission

Answer 34

each nucleus which spitso ut gives out a lot of energy in the kenetic stores of the fission products

Question 35

what does a nuclear reactor need
and what needs to be controlled

Answer 35

a chain reaction to keep it runing

when it is producing energy at the required rate 2 things need to be controlled:
the number of free neutons in the reactor
the energy in the free neutrons

Question 36

what do control rods do

Answer 36

often made of boron they limit the rate of fission by absorbing excess neutrons

Question 37

what does the moderator do

Answer 37

usually made of prapgie or water it slows down the neutrons

Question 38

how does a nuclear reactor work

Answer 38

Question 39

what is nuclear fusion

Answer 39

when 2 light nuclei collide at high speed and join (fuse) to create a larger and heavier nucleus

Question 40

energy in fusion

Answer 40

it relases a lot of energy

Question 41

what is the sheilding layer in a reactor for

Answer 41

it prevents any radiation from escaping even neutrons

Question 42

what is fusion an example for

Answer 42

the energy source for stars

Question 43

2 points for fusion

Answer 43

it only happens at REALLY high pressure and temperature

this is because the positivley charged nuclei have to get very close to fuse so they have to be moving very fast to overcome the strong force

Question 44

difference between fission and fusion

Answer 44

fusion: 2 nuclei of lighter elements combine to make a nucleus of a larger element

fission: the nucleus splits into 2 smaller nuclei