Energy from the nucleus

Question 1

Nuclear fission

Answer 1

The process in which uranium-235 and plutonium -239 split into two fragments, releasing energy and two or three neutrons as a result

Question 2

Chain reaction

Answer 2

Reactions in which one reaction causes further reactions. A nuclear chain reaction occurs when fission neutrons cause further fission

Question 3

Nuclear fusion

Answer 3

The process in which small nuclei are forced together so they fuse with each other to form a larger nucleus

Question 4

Gravitational attraction

Answer 4

The force that pulls masses together

Question 5

Star

Answer 5

A large ball of gas in space that emits radiation

Question 6

Galaxy

Answer 6

A collection of billions of stars, held together by their own gravity

Question 7

Protostar

Answer 7

The concentration of dust clouds and gas in space that forms a star

Question 8

Main sequence star

Answer 8

The main stage in the life of a star, during which it radiates energy because of fusion of hydrogen nuclei in its core

Question 9

Red giant

Answer 9

A star that has expanded and cooled, resulting in it becoming red and much larger than it was before it expanded

Question 10

White dwarf

Answer 10

A star that has collapsed from the red giant stage to become much hotter and denser than it was

Question 11

Black dwarf

Answer 11

A star that has faded out and gone cold

Question 12

Supergiant

Answer 12

A massive star that becomes much larger than a giant star when fusion of helium nuclei commences

Question 13

Supernova

Answer 13

The explosion of a massive star after fusion in its core ceases and the matter surrounding its core collapses on to the core and rebounds

Question 14

Neutron star

Answer 14

The highly compressed core of a massive star that remains after a supernova explosion

Question 15

Black hole

Answer 15

An object in space that has so much mass that nothing, not even light, can escape from its gravitational field

Question 16

What is nuclear fission?

Answer 16

Nuclear fission is the splitting of a nucleus into two approximately equal fragments and the release of two or three neutrons

Question 17

Which radioactive isotopes undergo fission?

Answer 17

Uranium-235 and plutonium-239

Question 18

What is a chain reaction?

Answer 18

A chain reaction occurs in a nuclear reaction when each fission event causes further fission events

Question 19

How is a chain reaction in a nuclear reactor controlled?

Answer 19

In a nuclear reactor, control rods absorb fission neutrons to ensure that, on average, only one neutron per fission goes on to produce further fission

Question 20

What is nuclear fusion?

Answer 20

Nuclear fusion is the process of forcing two nuclei close enough together so they form a single larger nucleus

Question 21

How can nuclei be made to fuse together?

Answer 21

Nuclear fusion can be brought about by making two light nuclei collide at very high speed

Question 22

Where does the Sun’s energy come from?

Answer 22

Energy is released when two light nuclei are fused together. Nuclear fusion in the Sun’s core releases energy

Question 23

Why is it difficult to make a nuclear fusion reactor?

Answer 23

A fusion reactor needs to be at a very high temperature before nuclear fusion can take place. The nuclei to be fused are difficult to contain

Question 24

What is radon gas and why is it dangerous?

Answer 24

Radon gas is an α-emitting isotope that seeps into houses in certain areas through the ground

Question 25

How safe are nuclear reactors?

Answer 25

There are thousands of fission reactors safely in use in the world, and none of them are of the same type as the Chernobyl reactors that exploded

Question 26

What happens to nuclear waste?

Answer 26

Nuclear waste is stored in safe and secure conditions for many years after unused uranium and plutonium (to be used in the future) is removed from it

Question 27

What was the universe like in the billions of years before stars and galaxies were formed?

Answer 27

Before galaxies and stars were formed, the universe was a dark patchy cloud of hydrogen and helium

Question 28

What is the force responsible for the formation of stars and galaxies?

Answer 28

The force of gravity pulled matter into galaxies and stars

Question 29

What are the stages in the life of a low mass star?

Answer 29

protostar → main sequence star → red giant → white dwarf → black dwarf

Question 30

What are the stages in the life of a high mass star?

Answer 30

protostar → main sequence star → red supergiant → supernova → neutron star → black hole (if sufficient mass)

Question 31

What will eventually happen to the Sun?

Answer 31

The Sun will eventually become a black dwarf

Question 32

What is a supernova?

Answer 32

A supernova is the explosion of a supergiant after it collapses

Question 33

What chemical elements are formed inside stars?

Answer 33

Elements as heavy as iron are formed inside stars as a result of nuclear fusion

Question 34

What chemical elements are formed in supernovae?

Answer 34

Elements heavier than iron are formed in supernovae supernovae, as well as light elements

Question 35

Why does the Earth contain heavy elements?

Answer 35

The Sun and the rest of the Solar System were formed from the debris of a supernova