P7 - Radioactivity

Question 1

define nuclear radiation

Answer 1

particles or waves emitted from an unstable nucleus

Question 2

define ionising radiation

Answer 2

particles or waves that have enough energy to remove or “knock off” electrons from their shells. This causes atoms to become ions.

ionising - making an ion

Question 3

Name 3 sources of background radiation

Answer 3

• Plants
• Animals
• Minerals
• Cosmic rays
• Industrial / Hospital waste

Question 4

define background radiation

Answer 4

ionising radiation which is present in an environment

Question 5

What is the difference between ionising radiation and nuclear radiation

Answer 5

All types of nuclear radiation are also ionizing radiation, however, ionising radiation doesn’t need to be emitted from a nucleus.

Question 6

Name 4 types of nuclear radiation

Answer 6

• Alpha α
• Beta β
• Gamma γ
• Neutron n

Question 7

What is the penetrating power of each type of radiation?

in air, and what stops it

Answer 7

α - centimeters in air | stopped by paper
β - meter in air | stopped by aluminium
γ - kilometers in air | stopped by lead

Question 8

List the properties of α radiation

Answer 8

• particle
• helium nucleus (2 protons 2 neutrons)
• ⁴₂He

Question 9

List are the properties of β radiation

Answer 9

• particle
• high speed electron
• ⁰_-1e

Question 10

List are the properties of γ radiation

Answer 10

• wave
• no mass, no charge

short wavelength photon

Question 11

When and why does gamma decay occur?

Answer 11

Gamma decay occurs after alpha or beta decay if the nucleus has extra energy.

Question 12

What happens during beta decay?

Answer 12

During beta decay, a neutron (ve) turns into a proton (+ve) which emits an β particle (electron -ve)

Question 13

alpha decay of

²³⁸₉₂U

→ Th

Answer 13

²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He

Question 14

beta decay of

¹⁴₆C

→ N

Answer 14

¹⁴₆C → ¹⁴₇N + ⁰_-1e

Question 15

define activity

Answer 15

overall rate of decay of unstable nuclei in a sample

Question 16

formula activity

radioactivity module

Answer 16

activity = count of decays / time
Bq = count / s

Question 17

Why does neutron decay occur?

Answer 17

Some radioactive nuclei emit a neutron n when a collision with the nucleus and an α particle occurs

Question 18

What is activity measured in?

Answer 18

Bq - Becquerels

Question 19

define half-life

Answer 19

The time it takes for half the nuclei in a substance to radioactivly decay

Question 20

define irradiation

Answer 20

exposing an object to beams of radiation

Question 21

define contamination

Answer 21

introducing a radioactive substance into or onto an object

Question 22

Is radioactive decay predictable?

Answer 22

No, radioactive decay is random.

Question 23

Name 3 uses of radioactive decay

Answer 23

• Smoke detectors. Americium-241 emits α particles which are used in a circuit; α particles are stopped by smoke.
• Measuring thickness of paper. Counting how many β particles travel through paper to hit a Geiger counter.
• Irradiating food. Cobalt-60 emits γ waves which kill bacteria on food without affecting the food.

Question 24

List the steps of a nuclear fission reaction

Answer 24

1. A nucleus absorbs a neutron
2. This nucleus splits into two daughter nuclei, releases 2-3 high-speed neutrons, and releases energy in the form of gamma radiation and KE
3. This process repeats. This is called a chain reaction

Question 25

What are fission fuel rods composed of?

Answer 25

3% Uranium-235 and 97% Uranium-238

Question 26

Name the components in a nuclear reactor

Answer 26

• Moderator (water and graphite)
• Fuel rods (enriched Uranium)
• Control rods (boron)
• The coolant (water)

Question 27

What does the moderator do in a nuclear reactor?

Answer 27

It slows down fission neutrons to help maintain the chain reaction

Question 28

What do the control rods do in a nuclear reactor?

Answer 28

They absorb neutrons to help maintain the chain reaction

Question 29

What does the coolant do in a nuclear reactor?

Answer 29

It transfers energy from the reactor to be converted into electrical energy. It is also used to cool the reactor.

Question 30

define nuclear fusion

Answer 30

A reaction where 2 nuclei are joined which produces a heavier nucleus and releases energy and a neutron

Question 31

define nuclear fission

Answer 31

A reaction where a nucleus is split which produces 2 smaller nuclei and releases energy and 2-3 neutrons

Question 32

What are the pros of nuclear fusion?

Answer 32

• It releases a lot of energy
• It doesn’t release greenhouse gases
• It doesn’t produce radioactive waste

Question 33

What are the cons of nuclear fusion?

Answer 33

• It requires a high-pressure and high-temperature environment
• It’s expensive
• It’s technologically difficult to achieve

Question 34

What instrument can be used to detect radioactivity?

Answer 34

A Geiger counter consists of a Geiger-Müller tube (Geiger tube) and an electronic counter.

Question 35

define Sievert (Sv)

Answer 35

A sievert is a unit of measurement that shows radiation dose.

Question 36

Does total mass increase or decrease after fission and fusion reactions?

Answer 36

the total mass decreases