P2.7 Energy From The Nucleus

Question 1

When does nuclear fission occur?

Answer 1

When a stable isotope is struck by a neutron. The isotope absorbs the neutron, becomes unstable and splits apart, releasing large amounts of energy.

Question 2

What isotopes undergo nuclear fission?

Answer 2

Uranium-235

Plutonium-239

Question 3

What do you need for a chain reaction?

Answer 3

Neutrons

Question 4

When fission occurs, what does it split into?

Answer 4

Daughter nuclei

Question 5

Draw a chain reaction.

Answer 5

Look it up

Question 6

What the danger with chain reactions?

Answer 6

They release a lot of energy very quickly and if it’s uncontrolled heat builds up and could explode.

Question 7

How are neutrons controlled?

Answer 7

The reactors graphite core slows down released neutrons so chain reaction can keep going.
Control rods made of boron absorb excess neutrons to prevent chain reactions getting out of control.

Question 8

Draw a reactor for nuclear fission.

Answer 8

Look it up

Question 9

How does nuclear fission start?

Answer 9

A uranium-235 atom absorbs a low speed neutron

Question 10

What are pros of nuclear fission?

Answer 10

Reduces use of fossil fuels
No greenhouse gases produced
Cheap to run once built

Question 11

What are cons of nuclear fission?

Answer 11

Expensive to build new power stations
Produces long lasting nuclear waste
Risk of uncontrolled chain reactions.

Question 12

What’s nuclear fusion?

Answer 12

Powers the sun and other stars.

Small nuclei join together to form larger nuclei and energy is released.

Question 13

What are deuterium and tritium?

Answer 13

Isotopes of hydrogen

Question 14

Deuterium + tritium ->

Answer 14

Fusion -> helium + neutron

Question 15

What conditions does nuclear fusion happen in?

Answer 15

In stars
High temp
High pressure

Question 16

What’s a life cycle for a star about the same size as our sun?

Answer 16

Protostar
Main sequence star
Red giant
White dwarf
Black dwarf

Question 17

What’s the life cycle for a star bigger than our sun?

Answer 17

Protostar
Main sequence star
Red super giant
Supernova
Then either neutron star or a black hole

Question 18

How do all stars start?

Answer 18

Nebula

Large clouds of dust and gas (mainly hydrogen)

Question 19

Give details of a protostar

Answer 19

Over millions of years gravity will cause dust&gas in the nebulae to come together. As it does this the temperature increases until hydrogen can fuse. When this happens a protostar is born. This is a star nursery.

Question 20

Give details of a main sequence star

Answer 20

Next stage after protostar. Hydrogen fusion has been happening and the star is much hotter and brighter than the protostar.

Question 21

Give details of a red giant star

Answer 21

When a star runs out of hydrogen it begins to fuse other heavier elements. This releases more energy causing the star to expand. It also gives off red light, hence the name.

Question 22

Give details of a white dwarf.

Answer 22

When the red giant runs out of fuel and can fuse nothing more it will lose its outer layers. This leaves just the core which is still extremely hot. It’s so hot it glows white hot giving its name.

Question 23

Give details of a black dwarf.

Answer 23

After a long enough time the white dwarf will cool down enough so that it stops glowing white hot. Now called black dwarf.

Question 24

Give details of a red super giant star

Answer 24

Following the main sequence the star begins to fuse together heavier elements. However, as it has far more fuel, it expands to a much larger size and gives off much more energy.

Question 25

What can a red super giant star fuse? Why’s it significant?

Answer 25

Elements up to iron

Iron is the most stable element in the universe

Question 26

Give details for a supernova

Answer 26

For very heavy stars, once they have run out of fuel, the star begins to collapse in on itself. It continues to collapse until it reaches a critical point when it can’t collapse anymore. This cause a massive shockwave. This naturally produces elements above iron. Outer layers expand outwards. Even though it lasts seconds, it’s the largest explosion known to man.

Question 27

Give details for a neutron star.

Answer 27

After a supernova, only the stars core is left behind. During the collapsing process, this core is turned into just neutrons. The resulting neutron star is very very dense.

Question 28

Give details on a black hole

Answer 28

In some very rare cases, the core of a star left over a supernova will co tinge to collapse. It will keeps getting smaller and smaller until the whole star has collapsed into an infinitely small point. It has an immense gravitational force, not even light can escape from it.

Question 29

Why are lots of elements formed?

Answer 29

In stars

Question 30

Does fission or fusion produce nuclear weapon materials?

Answer 30

Nuclear fission

Question 31

Does fission or fusion use hydrogen isotopes?

Answer 31

Fusion

Question 32

Does fission or fusion use an uranium isotope?

Answer 32

Fission

Question 33

Why fission or fusion has a highly radioactive process?

Answer 33

Fission

Question 34

Which out of fusion and fission is technically difficult?

Answer 34

Fusion

Question 35

Which out of fusion and fission produces no radioactive waste?

Answer 35

Fusion

Question 36

Which fission or fusion needs control rods for safety?

Answer 36

Fission

Question 37

Which fission or fusion process powers the sun?

Answer 37

Fusion