Nuclear Fusion (Chapter 4.3)

Question 1

What is nuclear Fusion

Answer 1

Nuclear fusion occurs when two small nuclei are combined (fuse) to form a larger nucleus

Question 2

What is the problem with nuclear fusion and under what circumstances will it occur? (4 marks)

Answer 2

Nuclei are positively charged and therefore exert electrostatic repulsion.

Nuclear fusion can occur if the nuclei have enough kinetic energy to overcome the repulsive force.

or

Nuclear fusion may occur at small separation distances as nuclear force dominates. However this requires an enormous amount of energy.

Question 3

Why cant nuclear fusion take place with large separation distances

Answer 3

As electrostatic force dominates the strong nuclear force and atoms repel

Question 4

What is binding energy and what does it show (3 marks)

Answer 4

Mass defect of the nucleus, energy that holds the nucleus together

shows how much energy is needed to separate the nucleus into individual nucleons

Higher binding energy = Stable nucleus

Question 5

how does fusion in the sun support life on earth

Answer 5

The fusion of hydrogen nuclei in the sun to form helium results in a mass defect almost 4 million tonnes due to the fusion of 653 million tonnes of hydrogen every second. A small proportion of this reaches earth and is used to sustain life via photosynthesis

Question 6

What is the main obstacle in using nuclear fusion as a method of sustaining electricity

Answer 6

An extremely high temperature of 100 million degrees must be achieved in order to commence fusion.

temperature must be contained within a reactor.

Current fusion reactors cant achieve this high temp for more than a couple seconds

Question 7

What is the biggest advantage of nuclear fusion electricity

Answer 7

energy produced per nucleon is greater than fission reactions

Massive amounts of energy could be obtained from few fusion reactions involving only a small number of nucleons with no radioactive by-products