P4 : Nuclear Fission and Nuclear Fusion

Question 1

Nuclear Fission

Answer 1

. In some elements, the nucleus is large and unstable
. In nuclear fission, the nucleus of these elements splits

Question 2

Nuclear Fission in Uranium

Answer 2

. When a uranium nucleus absorbs a neutron, this triggers the nucleus to undergo fission (split)
. When the nucleus splits, it forms two smaller nuclei roughly equal in size
. It also emits two or three neutrons plus gamma radiation
. Energy is also released during the fission reaction. All of the fission products have kinetic energy
. The neutrons can now be absorbed by more uranium nuclei and trigger fission again
. This is called a chain reaction

Question 3

What can controlled chain reactions be used for

Answer 3

To release energy in a nuclear reactor

Question 4

What are uncontrolled chain reactions used for

Answer 4

Used for explosions in nuclear weapons

Question 5

Nuclear fusion

Answer 5

In nuclear fusion, two light nuclei (eg hydrogen) are joined to form a heavier nucleus
. Some of the mass of the nuclei can be converted into energy which is released as radiation
.