P2.6 Nucleur Fission and Nucleur Fusion

Question 1

What is nuclear fission?

Answer 1

When an atomic nucleus splits up to form two smaller nuclei

Question 2

What is nuclear fission used for?

Answer 2

It produces a lot of energy, and is used in power stations to generate electricity

Question 3

How does nuclear fission occur?

Answer 3

When a slow-moving neutron is absorbed into a uranium or plutonium nucleus - making it unstable and thus forcing them to split

Question 4

What is released once a nucleus undergoes nuclear fission?

Answer 4

Neutrons

Question 5

Why is there a chain reaction in nuclear fission?

Answer 5

Because the neutrons released can go be absorbed by other nuclei which results them to split and release neutrons and…

Question 6

How is nuclear fission used as a way of generating electricity?

Answer 6

The energy released from nuclear fission is in the form of heat energy - the heat from nuclear fission is used to heat a coolant which is used to boil water, the steam produced is then used to turn a turbine which is connected to a generator

Question 7

What are the problems with nuclear power? (3)

Answer 7

The radioactive waste produced can’t be thrown away and it’s difficult and expense to dispose of it safely, nuclear fuel is cheap but running costs are expensive, at risk of radiation leaks and/or major catastrophes like Chernobyl

Question 8

What is nuclear fusion?

Answer 8

The combination of two nuclei which create larger nuclei

Question 9

What produces more energy, fusion or fission?

Answer 9

Fusion

Question 10

What are the benefits of fusion over fission as a source of energy?

Answer 10

Produces less waste and hydrogen is the product used in fusion which there is an abundance of

Question 11

What are the drawbacks of fusion over fission as a source of energy?

Answer 11

Fusion requires a very high temp. and atm, fusion reactors use more energy to heat them up than they actually produce, you also need a very strong magnetic field so the hydrogen can be held at such a high temp. and pressure

Question 12

How are stars formed?

Answer 12

Stars form from clouds of dust and gas, gravity forces the dust and gases to spiral together to form a protostar (where the GPE is converted into heat energy) - when the temp gets high enough, fusion occurs which gives out heat and light (this is a star)

Question 13

How are planets formed?

Answer 13

Small masses of gas and dust around the star are pulled together to make planets which orbit the star

Question 14

What phase of a stars life is the beginning of it’s life?

Answer 14

Main sequence stars - a star’s most stable point in it’s life, the heat created by fusion (pushing outwards) is equal to the force of graving pulling into the star

Question 15

What fuses when the hydrogen runs out in the main sequence star?

Answer 15

Heavier nuclei are fused - all elements up to iron

Question 16

What happens to a star (about the same size as our sun) when the hydrogen runs out?

Answer 16

It will expand into a red giant (red as it cools), which is unstable and ejects outer layers of dust and gas as planetary nebula

Question 17

What is left behind when a red giant ejects it’s outer layers?

Answer 17

A white dwarf, which cools down to form a black dwarf and eventually disappears from sight

Question 18

What happens to a star (larger than the size of our sun) when the hydrogen runs out?

Answer 18

A red super giant is formed - they are much bigger than red giants and burn for much longer

Question 19

What eventually happens to red super giants?

Answer 19

They explode into supernovas, forming elements heavier than iron and ejecting them into the universe to form new planets and stars

Question 20

What is made when a supernova explodes? (2)

Answer 20

A very dense core called a neutron star, or, if the star is a big enough, a black hole