P7- Radioactivity

Question 1

What do radioactive substances contain

Answer 1

Unstable nuclei that become stable by emitting radiation randomly

Question 2

Isotope

Answer 2

Atoms with the same number of protons, different number of neutrons

Question 3

Describe the five scientists and discoveries in order

Answer 3

Dalton, invisible objects
Thomson, plum pudding model
Rutherford, nuclear model and nucleus
Bohr, electron shells
Chadwick, neutrons and protons

Question 4

3 main types of radiation

Answer 4

Alpha
Beta
Gamma

Question 5

Thomson’s model

Answer 5

Positively charged cloud, with negative electrons scattered throughout

Question 6

Chadwick’s model

Answer 6

Proton-neutron model
Discovered neutrons

Question 7

Bohr’s model

Answer 7

Introduced electron shells. In line with Rutherford’s discovery

Question 8

Why was Thomson’s model no longer accepted?

Answer 8

His plum pudding model had no nucleus, only electrons in a positive cloud. Rutherford discovered the nucleus

Question 9

Atomic number
Mass number

Answer 9

Number of protons in nucleus
Number of protons plus neutrons in the nucleus

Question 10

Alpha particle experiment
Who?
What happened?
What did it prove?

Answer 10

Rutherford fired alpha particles at thin gold foil
Particles scattered and some reflected back
Proved tiny, massive, positive, central nucleus

Question 11

Alpha particle
Description?
Charge?
Relative atomic mass?

Answer 11

2 protons, 2 neutrons, no electrons
2+
4

Question 12

Alpha particle
Penetration?
Ionising effect?
Uses?

Answer 12

Stopped by single piece of paper, few cm in air
Strongest
Smoke detectors

Question 13

Beta particle
Description?
Charge?
Relative atomic mass?

Answer 13

Neutron splitting to 1 proton, 1 electron, electron emitted
-1 No mass

Question 14

Beta particle
Penetration?
Ionising effect?
Uses?

Answer 14

Stopped by mm of aluminium, few m in air
Moderate
Determine thickness of paper

Question 15

Gamma rays
Description?
Charge?
Relative atomic mass?

Answer 15

Waves of electromagnetic radiation
No charge or mass

Question 16

Gamma ray
Penetration?
Ionising effect?
Uses?

Answer 16

Stopped by thick lead, few km in air
Weak
Detect leaks in pipes

Question 17

Activity definition
Unit and measuring device?

Answer 17

Number of decays per second, Becquerels (Bq)
Geiger Muller tube

Question 18

Alpha particle calculations
Mass and atomic number

Answer 18

Mass number= decreases by 4
Atomic number= decreases by 2

Question 19

Beta particle calculations
Mass and atomic number

Answer 19

Mass number= stays same
Atomic number= increases by 1

Question 20

Half life

Answer 20

The time it takes for the activity to fall to half it’s starting level

Question 21

Half life equation

Answer 21

Count rate after n years= initial count/ 2 to the power of n

Question 22

Nuclear fission

Answer 22

The process of splitting atomic nuclei, can be used to produce energy for electricity

Question 23

4 Steps to nuclear fission process

Answer 23

1.Neutron absorbed by nucleus
2. Nucleus splits into 2 daughter nuclei
3. Produces energy and 2 or 3 neutrons
4. Happens in chain reaction

Question 24

In a nuclear reactor..
Role of water?
Role of control rods?
Role of concrete walls?

Answer 24

Slows down the emitted neutrons as they collide with water molecules
Absorbs surplus neutrons, controls chain reaction
Absorbs ionising radiation

Question 25

What are the two uses of radiation in medicine

Answer 25

Diagnosis- monitoring internal organs Treatment- control or destruction of unwanted tissue

Question 26

Radioactive tracer How? Use? What type?

Answer 26

Eating or injecting a harmless radioactive material To trace a substance e.g water, through an organ Gamma, detected outside body, low harm

Question 27

Radiotherapy How? Use? What type?

Answer 27

High doses of gamma rays Kills cancerous cells Gamma, high penetration

Question 28

Radioactive implants How? Use? What type?

Answer 28

Small pellets in body Kills cancer cells over time Beta or gamma with short half-lives

Question 29

Why is the half life important in medical treatments?

Answer 29

Needs to last long enough for the test to be complete, but decay soon after

Question 30

Why is the type of radiation important in medical treatments?

Answer 30

Must be detected outside of the body, could need to be strongly penetrating

Question 31

Examples of background radiation

Answer 31

Radon gas from the ground, food and drink, nuclear weapons testing

Question 32

Safety precautions of ionisation

Answer 32

Limit time, increase distance, use shielding

Question 33

Contamination

Answer 33

Unwanted presence of radioactive atoms on a material

Question 34

Irradiation

Answer 34

Exposing an object to radiation

Question 35

Ionisation

Answer 35

An atom becoming charged due to losing electrons

Question 36

Examples of contamination

Answer 36

Fish living in the sea around a nuclear power plant Breathing in radon gas Drinking tea with radioactive atoms

Question 37

Examples of irradiation

Answer 37

Treating fruit with gamma rays to kill bacteria Sterilising surgical instruments

Question 38

Factors of contamination

Answer 38

Radioactive source is on or in the object Difficult to remove all contamination Radiation can't be blocked

Question 39

Factors of irradiation

Answer 39

Object is exposed to radiation Stops as soon as the source is removed Can be blocked with shielding

Question 40

Nuclear fusion

Answer 40

Two nuclei fuse together to make a heavier nucleus

Question 41

4 Steps to nuclear fusion in stars process

Answer 41

1. 2 hydrogen nuclei fuse together 2. Forms a helium nucleus 3. Releases energy 4. Need high temp and pressure

Question 42

6 features of nuclear fusion

Answer 42

Uses Hydrogen as fuel Joining of two atoms Takes place in the sun Fuel is easily available Harmless product Needs high pressure and temp

Question 43

5 features of nuclear fission

Answer 43

Uses Uranium as fuel Splitting of an atom Causes chain reaction Often used on earth Produces nuclear waste

Question 44

2 similarities of nuclear fusion and fission

Answer 44

Produces energy, can generate electricity Have been used in a bomb