Topic 5 - Nuclear Fission and Nuclear Fusion

Question 1

What does the mass number tell you about the nucleus of an atom?

Answer 1

Total number of protons and neutrons

Question 2

What does the atomic number tell you about the nucleus of an atom?

Answer 2

The number of protons/electrons

Question 3

what are isotopes?

Answer 3

Different form of the same element. They have the same number of protons and electrons but a different number of neutrons.

Question 4

Which number is always the same for isotopes?

Answer 4

Atomic number

Question 5

What does it mean to say that radioactive decay is random?

Answer 5

There is no way of knowing when an atom will decay and you can not force an atom to decay either

Question 6

What is emitted when an unstable nuclei decays?

Answer 6

radiation

Question 7

What are the three types of ionising radiation given off by unstable nuclei?

Answer 7

Alpha
Beta
Gamma

Question 8

Describe what happens when an atom is ionised

Answer 8

It gains or loses electrons so becomes charged

Question 9

Describe what an alpha particle is, how strongly it ionises, how well it penetrates, and what materials block it

Answer 9

2 protons 2 neutrons (helium nucleus)
Very ionising
Not very penetrating
It can be stopped by air, paper, human hand.

Question 10

Describe what a beta particle is, how strongly it ionises, how well it penetrates, and what materials block it

Answer 10

electron
average ionisation
average penetration
blocked by thin sheet of aluminium

Question 11

Describe what a gamma ray is, how strongly it ionises, how well it penetrates, and what materials block it

Answer 11

gamma wave
not very ionising
highly penetrating
stopped by many centimetres of lead or many metres of concrete.

Question 12

What is nuclear fission?

Answer 12

splitting up of an unstable atom to produce energy

Question 13

How does nuclear fission happen?

Answer 13

slow moving neutron is fired at an isotope of uranium (uranium 235). the neutron is absorbed by the nucleus and causes it to split. It then forms two daughter nuclei and thermal energy is released. It also spits out more neutrons (two or three) which hit other nuclei and the process begins again

Question 14

What is the energy transfer in a nuclear power station

Answer 14

Nuclear -> thermal -> kinetic -> electrical

Question 15

What happens in a nuclear power station?

Answer 15

in a nuclear reaction a controlled chain fission reaction happens, the heat energy is used to boil water to drive a steam turbine, which turns a generator to generate electrical energy

Question 16

How can we control the chain reactions in reactors?

Answer 16

1) uranium fuel rods are placed in a moderator (e.g graphite) to slow down the fast moving neutrons.
2) control rods made of boron limit the rate of fission by absorbing excess neutrons. They are placed in between the fuel rods and are raised and lowered to control the chain reaction.
3) A coolant (water or co2) is pumped through the reactor to keep the reaction at a certain temperature.

Question 17

What happens to an atom when they undergo nuclear fusion?

Answer 17

two nuclei collide at high speed and fuse to create a larger nucleus.

Question 18

Does fusion happen with big or small atoms?

Answer 18

Small

Question 19

is more energy released in fission or fusion?

Answer 19

fusion

Question 20

Does fusion produce a lot of waste?

Answer 20

No

Question 21

Where does fusion occur naturally?

Answer 21

In stars

Question 22

What conditions are needed for fusion to occur

Answer 22

High temperatures and pressures

Question 23

Why are there no practical fusion power stations?

Answer 23

Incredibly difficult to create conditions needed. Uses more power to get to right temperature than the fusion produces.
Expensive

Question 24

What is cold fusion?

Answer 24

nuclear fusion that occurs around room temperature.

Question 25

Why would cold fusion be an important discovery?

Answer 25

It would make it possible to create generate lots of electricity easily and cheaply.

Question 26

How should scientists announce their results?

Answer 26

publish to journals
peer-review
reproduction of results