radioactivity

Question 1

Why do some atoms emit radiation?

Answer 1

Because they have unstable nuclei that can only stabilise by emitting radiation.

Question 2

3 types of radiation

Answer 2

Alpha
Beta
Gamma

Question 3

Relative mass of electrons

Answer 3

1/2000

Question 4

Relative mass of protons

Answer 4

1

Question 5

Relative mass of neutrons

Answer 5

1

Question 6

Alpha Radiation

Answer 6

α
2 protons + 2 neutrons.
Relative mass of 4
Stopped by paper
5 cm range in air
Greatest ionising powe

Question 7

Beta Radiation

Answer 7

B
Relative mass of 0
Charge of -1
A neutron in the nucleus changes into a proton and an electron. The electron is expelled from the atom but the proton stays.
Stopped by aluminium
1m range in air
Medium ionising power

Question 8

Gamma Radiation

Answer 8

Y
Uncharged and has no mass- is a form of electromagnetic radiation.
Doesn't change the element etc.
stopped by lead.
Unlimited range in air.
Least ionising power.

Question 9

Half Life

Answer 9

The time it takes for the number of nuclei of the isotope in a sample to halve.

Question 10

Nuclear Fusion

Answer 10

The process in which small nuclei are forced together so they fuse with each other to form a larger nucleus.

Question 11

Sources of Background Radiation

Answer 11

> Cosmic Rays
> Food and Drink
> Medical Treatments (e.g X-rays)
> Air Travel
> Ground and Buildings
> Natural Radioactivity in the Air.
> Nuclear weapons Testing.
> Nuclear Power.

Question 12

Effect of Alpha radiation from a source outside the body

Answer 12

Very dangerous- Affects all surrounding tissue

Question 13

Effect of Alpha radiation from a source inside the body.

Answer 13

Possible Danger- absorbed by skin, can damage skin + retina cells.

Question 14

What is alpha decay?

Answer 14

• alpha particle ejected from nucleus
• made of 2 protons and 2 neutrons
• 10% speed of light
• 5-8cm range, stopped by thin piece of paper
• highly ionising
• atomic mass - 4
• atomic number - 2

Question 15

What is beta decay?

Answer 15

• neutron turns into proton and electron
• proton stays but electron ejected
• up to 90% speed of light
• 5-10cm range, stopped by alfoil
• less ionising
• same atomic mass
• atomic number - 1

Question 16

What is gamma decay?

Answer 16

• nucleus, even after a or b decay can still be a bit energetic ∴ releases a gamma ray yo lose energy and become stable
• high grew, high energy em wave
• no structure/mass/charge
• trials at speed o’ light, readuced by lead and concrete
• Addley ionising

Question 17

What is radioactivity measured in?

Answer 17

Bequerels (Bq)

Quantity of radioactive material which 1 nucleus decays per second

Question 18

How can we calculate how much of a sample has decayed?

Answer 18

• you can’t- decay is random, but we can use stats to analyse
• measure in half lives, as the substance never fully decays
Half live = time taken for num f nuclei to halve OR time taken for activity of a sample to halve

Question 19

How do we measure ionising radiation?

Answer 19

With a photographic film of a Geiger-muller tube

Question 20

What do the control rods in a nuclear reactor do?

Answer 20

Chain reaction must happen at a steady rate tf we need control rods to control the speed of reaction. Made of boron which absorbs neutrons.
If lowered ⇒ reaction slower
If taken out ⇒ reaction faste

Question 21

What is the water for in a nuclear reaction?

Answer 21

• the neutrons must be moving slowly to be captured by the U nuclei so they can for a chain reaction
• the water acts as a moderator to slow down the neutrons ∴ making it easier for them to be captured
• also used as a coolant to remove the heat produced by the nuclear reactions ∴ can heat up the other separate water system to power a steam generator

Question 22

What do the fuel rods do?

Answer 22

Made of U 235
Produce lots of heat in the reactions ∴ warm up the coolant
Need to be replaced every 3 years as less efficient due to waste product

Question 23

Why is the nuclear reactor encased in a thick steel case, and then a concrete canister?

Answer 23

Steel case: keeps water at high pressure to stop it boiling

Concrete canister: stops gamma radiation escaping an harming workers

Question 24

neutron decay

Answer 24

0

1

Question 25

Describe the process of nuclear fission.

Answer 25

Nuclear fission is the splitting of a large atomic nucleus when a nucleus absorbs a neutron so an unstable nucleus splits and energy is released

Question 26

Describe the process of nuclear fusion

Answer 26

Nuclear fusion is the joining of two atomic nuclei to form a larger one