Nuclear fusion

Which of these is the main source of energy in stars?

The table lists the stages of development of a star that has a very much larger mass than the Sun.

Give the stages in the correct order, using numbers 1 to 5.

This question is about nuclear fission and nuclear fusion.

The table gives some statements about nuclear fission, or nuclear fusion, or both nuclear fission and nuclear fusion.

Place ticks (✓) in the table to show which statements are about nuclear fission and which statements are about nuclear fusion.

Nuclear fission reactors use control rods and a moderator.

Describe the function of the control rods and the function of the moderator in a nuclear fission reactor.

control rods

moderator

This question is about nuclear reactions.

Nuclear fusion and nuclear fission release energy from the nuclear stores of atoms.

The table gives some statements about nuclear fusion and some statements about nuclear fission.

Place ticks () in the table to show whether each statement applies to nuclear fusion or nuclear fission.

In nuclear fusion, two positively charged nuclei must overcome the effects of the repulsive electrostatic force between them.

Explain the two conditions needed to overcome the effects of this repulsive force and achieve nuclear fusion.

Describe how a chain reaction occurs in a nuclear fission reactor.

Describe the role of the control rods in a nuclear fission reactor.

Describe how the process of nuclear fission is different from the process of nuclear fusion.

Which of these is the name of the nuclear process that is the main energy source for stars?

Give a reason why the nuclear process in stars does not happen at low temperatures and pressures.

The photograph shows the nuclear fusion reactor called ITER.

Describe the difference between nuclear fusion and nuclear fission.

At ITER, hydrogen-3 and hydrogen-2 will be fused into helium and another particle labelled X.

Complete the nuclear equation for the fusion of hydrogen-3 and hydrogen-2.

Discuss potential safety advantages of a fusion reactor compared with a fission reactor.

You should refer to the products of this fusion reaction and to the fission reaction of uranium.

The half-life of a radioactive isotope is 12 years.

The activity of a sample of this isotope is 120 kBq.

Calculate the activity of this sample after 48 years.

Nuclear fusion is a process that occurs in the core of stars.

Which is the best description of nuclear fusion?

Two nuclei are close together and stationary.

Explain why these nuclei will move apart.

Describe the conditions needed for fusion to occur in the core of a star.

This question is about nuclear fusion.

The incomplete nuclear equation shows the fusion of two isotopes of hydrogen.

Identify particle X in the nuclear equation.

Each fusion reaction releases approximately 310^–12J of energy.

Estimate how many reactions are needed to produce 1 J of energy.

Give your answer to 1 significant figure.

Explain why this fusion reaction will only happen at high temperature and high pressure.

A tokamak is an experimental nuclear fusion reactor.

Strong magnetic fields are used to contain the reactants inside the tokamak.

The diagram shows a positively charged hydrogen nucleus in a uniform magnetic field directed out of the page.

magnetic field out of page

positively charged hydrogen nucleus

The nucleus experiences a force acting to the left because of the magnetic field.

Deduce how the nucleus must behave to experience this force.

Suggest how engineers working on the tokamak could increase the force on the nucleus.

In extreme conditions, the isotope lithium-6 can be made to undergo nuclear fission.

The lithium-6 nucleus absorbs a neutron and produces an alpha particle and an isotope of hydrogen.

The incomplete nuclear equation for this fission is

Complete the nuclear equation by writing the numbers in the boxes.

Explain why this fission does not cause a chain reaction.

Explain the difference between nuclear fission and nuclear fusion.

This question is about stars.

Describe the stages in the evolution of a star similar in mass to the Sun.

The process of energy release in the core of a star is different to the process of energy release in a nuclear reactor in a power station.

Describe how these processes of energy release are different.

This question is about Rigel, a very large star with a high surface temperature.

Stars can appear as different colours because of their different surface temperatures.

Which of these colours shows the highest surface temperature for a star?

Describe how a star is formed in a nebula.

Rigel is a main sequence star.

A star joins the main sequence when nuclear fusion of hydrogen starts in its core.

Describe the process of nuclear fusion in a star.

Astronomers think that Rigel will become a supernova in the future.

Which property of a star determines whether it will become a supernova?

Describe the evolution of Rigel after it leaves the main sequence.

Energy is transferred from the Sun to the Earth.

Nuclear fusion happens in the Sun.

Which energy store of the Sun decreases during nuclear fusion?

How is energy transferred through space from the Sun to the Earth?

Solar panels use energy from the Sun to heat water.

The total area of the solar panels is 15 m².

Each 1.0 m² of the solar panels receives 1000 J of energy per second from the Sun.

Show that the total energy transferred to the solar panels in 2 hours is about 100 MJ.

A mass of 1100 kg of cold water is in the solar panels at an initial temperature of 20C.

Calculate the final temperature of this water after it has been heated by the Sun for 2 hours.

[specific heat capacity of water = 4200 J/kg C]

final temperature _........ C

Give a reason why the actual final temperature of the water will be lower than the calculated value.

Some of the energy stored in the nuclei of atoms can be used to generate electricity.

A nuclear fission power station generates electricity.

State the role of the moderator in a nuclear fission power station.

Some of the daughter nuclei produced in nuclear fission are highly radioactive and emit high energy neutrons when they decay.

Explain which feature of a nuclear fission reactor reduces the risks from these high energy neutrons.

The daughter nuclei can cause contamination and irradiation.

Describe the difference between contamination and irradiation.

Nuclear fusion is another process that could be used to generate electricity.

Describe the process of nuclear fusion.

State where nuclear fusion occurs naturally.

Generating electricity from nuclear fusion is very difficult as the conditions needed are hard to achieve and maintain.

Explain the conditions required for nuclear fusion.