P2.6 - Energy From The Nucleus

Question 0

Which radioactive isotopes undergo fission?

Answer 0

Uranium-235

Plutonium-239

Question 1

What is nuclear fission?

Answer 1

The splitting of a nucleus and the release of two or three neutrons.

Question 2

What is a chain reaction in fission?

Answer 2

A chain reaction occurs in a nuclear reactor when each fission causes further fission.

Question 3

How is a chain reaction in a nuclear reactor controlled?

Answer 3

Control rods absorb fission neutrons to ensure that only one neutron per fission goes on to produce further fission.

Question 4

What does water do in a nuclear reactor?

Answer 4

Water slows down fission neutrons and acts as a coolant for the fuel rods.

Question 5

How is radiation contained in the reactor?

Answer 5

The core is made of thick steel and enclosed in thick concrete.

Question 6

What is nuclear fusion?

Answer 6

The process of forcing two nuclei close enough together so they form a single larger nucleus.

Question 7

How can nuclei be made to fuse?

Answer 7

Making two light nuclei collide at very high speed.

Question 8

Where does the Sun’s energy come from?

Answer 8

Nuclear fusion occurs in the Sun’s core which releases energy.

Question 9

Why is it difficult to make a nuclear fusion reactor?

Answer 9

• A reactor needs to be at a very high temperature before nuclear fusion can take place.
• The nuclei fused are difficult to contain.

Question 10

What is produced when hydrogen nuclei fuse?

Answer 10

“Heavy hydrogen”

Question 11

What is produced when two “heavy hydrogen” nuclei fuse?

Answer 11

A helium nucleus

Question 12

Why does nuclear fusion only take place at high temperatures?

Answer 12

The two nuclei will repel each other but if they are going fast enough, they can overcome the force of repulsion.

Question 13

Give three advantages of using nuclear fusion for energy.

Answer 13

• The fuel needed is readily available as heavy hydrogen and is present in sea water.
• The product, helium, is a harmless inert gas.
• The energy released can be used to generate electricity.

Question 14

What is radon gas?

Answer 14

An alpha-emitting isotope that can seep into houses in certain areas.

Question 15

What happens to nuclear waste?

Answer 15

Nuclear waste is stored in secure facilities after unused radioactive isotopes are recovered.

Question 16

Why is the Chernobyl disaster unlikely to be repeated?

Answer 16

• Most reactors have a different design.
• Chernobyl didn’t have a high-speed shut down system.
• Operators at Chernobyl ignored safety instructions.

Question 17

What three things does the effect of radiation on living cells depend on?

Answer 17

• Type and amount of radiation
• Whether the source is inside or outside the body.
• How long the cells are exposed.

Question 18

How do workers at risk of ionising radiation reduce their exposure?

Answer 18

• Keeping far away from the source of radiation.
• Spending as little time as possible in ‘at-risk’ areas.
• Shielding themselves from radiation.

Question 19

What is a galaxy?

Answer 19

A collection of billions of stars held together by their own gravity.

Question 20

What was the universe like before stars and galaxies were formed?

Answer 20

The universe was a dark patchy cloud of hydrogen and helium.

Question 21

Which force caused the formation of stars and galaxies?

Answer 21

Gravity

Question 22

When did quarks and electrons form in the Big Bang?

Answer 22

After 0.1s from radiation

Question 23

When did neutrons and protons form following the Big Bang?

Answer 23

After 100s.

Question 24

When did hydrogen and helium atoms form following the Big Bang?

Answer 24

After 100,000 years

Question 25

When were the first stars and galaxies formed?

Answer 25

After a few billion years.

Question 26

What is a protostar?

Answer 26

A gas and dust cloud in space that can go on to form a star.

Question 27

What are the stages in the life of a low mass star?

Answer 27

• Protostar
• Main sequence star
• Red giant
• White dwarf
• Black dwarf

Question 28

What are the stages in the life of a high mass star?

Answer 28

• Protostar
• Main sequence star
• Red supergiant
• Supernova
• Neutron star
• Black hole if there is enough mass

Question 29

What is a supernova?

Answer 29

The explosion of a supergiant after it collapses.

Question 30

How does a protostar form?

Answer 30

• The particles in a cloud are pulled together by their gravitational pull.
• The clouds merge and become more concentrated.

Question 31

What happens at the end of the main sequence of a star like the Sun?

Answer 31

They swell out, cool down and turn red. Light elements fuse to form heavier elements.

Question 32

What happens at the end of the red giant stage?

Answer 32

• When there are no more light elements, fusion stops.
• Due to its own gravity, the star collapses in.
• It heats and turns from red to a white dwarf.

Question 33

What happens at the end of the red supergiant stage?

Answer 33

• The star collapses.
• The matter surrounding the star’s core compresses the core.
• The compression suddenly reverses in a cataclysmic explosion.

Question 34

What elements are formed inside stars?

Answer 34

Elements up to the mass of iron are formed inside stars as a result of nuclear fusion.

Question 35

What chemical elements are formed in supernovas?

Answer 35

Elements heavier than iron are formed in supernovas.

Question 36

Why does the Earth contain heavy elements?

Answer 36

The Solar System was formed from the debris of a supernova.

Question 37

Why aren’t elements heavier than iron formed in stars by nuclear fusion?

Answer 37

Too much energy is needed.

Question 38

What evidence is there that the Solar System formed from the remnants of a supernova?

Answer 38

Uranium could only have been made in a supernova because of the energy needed.