Module 6 - 6.4.4 Nuclear Fission and Fusion

Question 1

When there is a decrease in the mass of a system

Answer 1

an amount of energy equivalent to the change in mass is released

Question 2

In annihilation reactions

Answer 2

the mass of the matter and antimatter disappear and a large amount of energy is released as photons of em radiation

Question 3

Mass Defect (definition)

Answer 3

The difference in mass between the mass of a nucleus and the total mass of its separate nucleons

Question 4

Binding Energy (definition)

Answer 4

The minimum energy required to separate the nucleus into its protons and neutrons

Question 5

The greater the binding energy per nucleon

Answer 5

the more stable the nucleus will be

Question 6

In a fission reaction (3)

Answer 6

• Unstable nuclei absorb slow moving neutrons
• to slip into smaller nuclei and a small number of neutrons
• to release energy and increase their stability

Question 7

In a nuclear power station (fission)

Answer 7

The energy released heats water into steam
which turns a generator to produce electricity

Question 8

Chain Reactions

Answer 8

If one of the neutrons released by a fission reaction, it can induce a further fission reaction causing a chain reaction

Question 9

Fission Reactors Contain (2)

Answer 9

Control Rods
- absorb neutrons to reduce the number of chain reactions
- done through moving the rods in and out of reactor

Moderator
- a neutron will only cause a fission reaction if travelling at the correct speed
- neutrons must be slowed down by a moderator in order to be absorbed

Question 10

Nuclear Waste (definition)

Answer 10

A radioactive material that is no longer useful

Question 10

Nuclear Waste Precautions (2)

Answer 10

• nuclear waste must be stored securely in shielded containers until no longer radioactive
• exposure to ionising radiation above the background level can cause harm to plant and animal life

Question 11

Fusion occurs when

Answer 11

nuclei of lighter elements fuse to increase their stability, producing heavier nuclei

Question 12

Fusion and Binding Energy

Answer 12

• the resulting nuclei have a binding energy greater than that of the combined energy of the individual nuclei that fused
• the difference in binding energy is released as the kinetic energy of the resulting particles and as photons

Question 13

Advantages of using fusion for power production (2)

Answer 13

• no radioactive waste products
• there is a virtually unlimited supply of the raw materials

Question 14

Problem with Fusion

Answer 14

• extremely high temperatures need to be maintained
• as energy needs to be supplied for fusion to occur in the first place