Nuclear fusion

The table in Figure 16 shows some data about four stars.

State which star in the table in Figure 16 is most likely to become a Black Hole.

Using data from the table in Figure 16, give a reason for your answer to part (i).

In a nuclear fusion reaction, mass is converted into energy.

Describe what is meant by nuclear fusion.

The speed of light, c, is 3.0 × 10⁸m / s.

The energy radiated by the Sun in 1 second is 3.9 × 10²⁶J.

Calculate the decrease in the Sun’s mass equivalent to this energy.

State the unit with your answer.

Use the equation

decrease in mass =_........

*(c) There have been a number of theories about the origin and development of the Universe.

One theory about the origin and development of the Universe is The Big Bang Theory.

Discuss two pieces of evidence that support The Big Bang Theory.

Figure 8 shows two types of force that act in the Sun.

One type of force acts inwards, towards the centre of the Sun.

The other type of force acts outwards, away from the centre of the Sun.

Outward forces are a result of nuclear fusion in the Sun.

State what causes the inward forces.

The inward and outward forces in stars like the Sun stay balanced for 10 billion years.

In the Sun, these forces have been balanced for 46 % of this time.

Calculate for how many billions of years these forces have been balanced in the Sun.

time =_........ billion years

Describe what will happen to the Sun when the inward and outward forces become unbalanced.

Nuclear fusion reactions take place in the Sun.

Describe what happens in a nuclear fusion reaction.

In 1989, two scientists claimed that they could produce a nuclear fusion reaction in their laboratory.

They said their reaction could take place at room temperature in a test tube.

Explain why other scientists did not believe them.

Nuclear fusion is a process that releases energy.

Which of these statements applies to a nuclear fusion reaction?

In the Sun, four protons start the process of nuclear fusion.

These protons combine and finally produce a helium nucleus.

The helium nucleus has a smaller mass than the four protons.

This difference in mass is converted to energy.

Four protons have a total mass of 6 69. 10²⁷ kg.

A helium nucleus has a mass of 6 64. 10²⁷ kg.

Calculate the percentage of the original mass that has been converted to energy.

percentage of mass converted to energy_........

Figure 1 shows the spectrum of an element detected in the light from a distant galaxy, from a nearby galaxy and from a source on Earth.

Estimate the difference between the wavelength of line P in the spectrum from the distant galaxy and the wavelength of line P in the spectrum on Earth.

Scientists have discovered that light from almost all distant galaxies has spectral lines shifted towards the red end of the spectrum.

Explain how red shift in light, received from galaxies at different distances from the Earth, supports the idea that the Universe is expanding.

This question is about stars.

Use words from the box to complete the following sentences.

Stars of similar mass to our Sun were formed from a cloud of gas and dust

Our Sun is a_........ star.

Which will be the next stage in the evolution of our Sun?

The core of a star with a much bigger mass than our Sun is most likely to end as a

A nuclear fusion reaction is happening in our Sun.

The nuclear fusion reaction produces helium and radiates energy.

State one of the conditions necessary for this nuclear fusion reaction to start.

Describe what happens in this nuclear fusion reaction.

The intensity of the Sun’s radiation in W/m² on the surface of Earth is 1.3210³.

The intensity of the Sun’s radiation in W/m² on the surface of Mars is 4.9210².

Calculate the ratio

intensity of the Sun’s radiation on the surface of Earth intensity of the Sun’s radiation on the surface of Mars

This question is about nuclear reactions.

When a uranium-235 (U-235) nucleus absorbs a neutron, the nucleus splits into smaller parts.

This reaction is called nuclear fission.

How many daughter nuclei are produced from the fission of one nucleus of uranium-235 (U-235)?

When a uranium-235 (U-235) nucleus splits, neutrons are also emitted.

The neutrons may start a chain reaction.

Describe what is meant by a chain reaction.

You may draw a diagram to help with your answer.

In the nuclear reactor of a power station, the chain reaction has to be controlled.

Explain the action of a moderator in a nuclear reactor.

In a nuclear reactor there are 2.010¹⁷ fission reactions each second.

Each fission reaction releases 4.010^–11J of energy.

Calculate the energy released in 1 second.

Nuclear fusion is a nuclear reaction that takes place in the Sun.

Describe what happens during a nuclear fusion reaction.

Figure 13 shows wind turbines, used to generate electricity for the National Grid.

The wind turns the turbine blades.

The wind is a renewable source of energy.

State two other renewable sources of energy.

For one turbine

• the energy input per second from the wind is 6.2 kJ

• the energy output per second to the National Grid is 2.2 kJ.

Calculate the efficiency of this turbine.

Suggest a reason why it is impossible for the turbine to use all the kinetic energy of the wind.

*(b) Nuclear fission and nuclear fusion are two non-renewable sources of energy.

Compare nuclear fission and nuclear fusion as possible sources of energy for generating electricity using a nuclear reactor.

Your comparison should refer to

• the differences between nuclear fission and nuclear fusion

• the relative advantages and difficulties involved in using these sources.

The Sun has a mass of 2.0 × 10³⁰kg. A white dwarf has a mass of 3.4 × 10²⁹kg.

Calculate the value of

mass of this white dwarf

Figure 18 is a diagram giving some information about main sequence stars. Luminosity is a measure of how bright something is. An increase in luminosity means an increase in brightness.

Estimate the temperature of the Sun.

State how the brightness of a main sequence star changes with its temperature.

State how the brightness of a main sequence star changes with its mass.

Nuclear fusion provides the energy source for stars including the Sun.

Describe what happens during nuclear fusion.

A nebula may evolve into a main sequence star, such as the Sun.

Explain how a nebula may evolve into a main sequence star.

Equations

The Sun has a mass of 2.0 × 10³⁰kg. A white dwarf has a mass of 3.4 × 10²⁹kg.

Calculate the value of

mass of this white dwarf

Figure 4 is a diagram giving some information about main sequence stars. Luminosity is a measure of how bright something is. An increase in luminosity means an increase in brightness.

Estimate the temperature of the Sun.

State how the brightness of a main sequence star changes with its temperature.

State how the brightness of a main sequence star changes with its mass.

Nuclear fusion provides the energy source for stars including the Sun.

Describe what happens during nuclear fusion.

A nebula may evolve into a main sequence star, such as the Sun.

Explain how a nebula may evolve into a main sequence star.

Stars may originate as a nebula.

Describe the process that then occurs to produce the conditions necessary for nuclear fusion in a new star.

The energy, E, released in nuclear fusion is equivalent to loss in mass, m, according to the equation.

where c is the velocity of light.

c = 3.0010⁸ m/s

In 1 second, the energy radiated by the Sun is 3.8610²⁶ J.

Calculate the loss in mass of the Sun in 1 second.

*(b) The Big Bang theory gives an explanation for the origin of the Universe.

Explain how evidence supports the ideas that

● the Universe is expanding

● the Universe began at a single point.

A star has evolved to become a neutron star.

The mass, M, of the neutron star, of radius R, is given by

Use the equation to calculate the value for R.

Figure 8 shows a helium nucleus.

Two of the particles in the helium nucleus are neutrons.

State the name of the other two particles in the helium nucleus.

Describe the difference between a fusion reaction and a fission reaction.

Nuclear fusion does not happen at low temperatures because of electrostatic repulsion between

The energy released per kilogram of fuel in a fusion reaction is 845 000 GJ.

The energy released per kilogram of fuel in burning oil is 0.0394 GJ.

Calculate the ratio of the energy released in fusion compared with the energy released in burning oil.

Use the equation

State two advantages of using a fusion reactor rather than burning oil in a power station.

State two of the difficulties that need to be overcome to produce a fusion reactor.

Fusion and fission are nuclear reactions in which large amounts of energy are released.

In a fusion reaction, two hydrogen nuclei are forced together to form a helium nucleus.

Explain why a very high temperature is needed for this reaction to happen.

In a fusion reaction, the combined mass of the two small nuclei is greater than the mass of the resulting nucleus.

This decrease in mass, m, appears as energy, E, according to the equation.

c is the speed of light = 3.0 × 10⁸ m/s.

The energy released in one fusion reaction is 4.5 × 10⁻¹² J.

Calculate the decrease in mass.

*(b) Nuclear fission is used in nuclear reactors in some power stations.

In the reactor, a fission chain reaction is maintained and controlled to produce a supply of energy to generate electricity.

Figure 14 is a diagram of a nuclear reactor.

Explain how the graphite core and the movable rods are used to maintain and control the chain reaction.