2- Energy From The Nucleus

Question 1

What are the two fissionable isotopes used commonly in nuclear reactors?

Answer 1

Uranium-235 (most often)

Plutonium-239

Question 2

What do most (uranium) nuclear reactors use and why?

Answer 2

Enriched uranium (235) because naturally occurring uranium is non-fissionable

Question 3

How does fission occur?

Answer 3

The fissionable isotopes nucleus must absorb a neutron. Then the nucleus splits into two smaller nuclei. Whist this happens, a few neutrons are emitted and a great amount of energy is released

Question 4

What does a control rod do in a nuclear reaction?

Answer 4

Absorb fission neutrons to ensure only one neutron per fission goes on to produce further fission on average

Question 5

What is nuclear fusion?

Answer 5

The process of forcing two nuclei close enough together to form a single, larger, nucleus - two light nuclei collide at high speed

Question 6

What is an example of nuclear fusion?

Answer 6

Process in which energy is released by stars

Question 7

What problems are faced when producing energy from nuclear fusion in reactors?

Answer 7

Nuclei will naturally repel each other so they must be heated to very high temperatures, because of this the reaction must be contained by a magnetic field

Question 8

What are the issues of everything nuclear?

Answer 8

Different sorts of background radiation

Question 9

What are some examples of nuclear background radiation?

Answer 9

Radon gas (from rocks deep underground) alpha particles emitted
Cosmic rays (outer space) 
Food and drink, air travel, nuclear weapon testing 
Medical sources (X-rays) have ionising effects

Question 10

What is useful about uranium and plutonium?

Answer 10

If stored properly, they can be chemically removed and used again

Question 11

What should workers do to reduce radiation exposure?

Answer 11

Keep as far away as possible
Spend as little time close as possible
Shield themselves with concrete and lead

Question 12

How do most scientists believe the universe was created?

Answer 12

Through ‘the big bang’.
From a hot glowing ball of radiation, nuclei of the lightest element formed. Over millions of years as the earth temperatures fell uncharged atoms were formed

Question 13

How were stars originally formed?

Answer 13

From a cloud of helium and hydrogen, dust and gas were pulled together by gravitational attraction to form stars. The intense heat formed visible light

Question 14

What is a galaxy and a bit about it?

Answer 14

A very large group of stars held together by their own gravity, our galaxy is called the Milky Way (one of billions of galaxy’s)
Each galaxy has masses of empty space between them

Question 15

How does a protostar form? How does it get hotter and brighter?

Answer 15

Gravitation forces pill clouds of dust and gas together to form a protostar
As it becomes denser, the nuclei of light elements (such as hydrogen) fuse together releasing energy which makes the core hotter and brighter

Question 16

What is a main sequence star and how does it form from a protostar?

Answer 16

As a protostar runs becomes denser, the star is stable because the inward force of gravity and outward force of radiation from the core are balanced. This process goes on for billions of years

Question 17

What happens when a main sequence star runs out of hydrogen nuclei?

Answer 17

It swells, cools down and turns red

Question 18

After a star runs out of hydrogen, what happens will depend on the stars size, if the main sequence star has a low mass, what will be formed and how?

Answer 18

A red giant, our sun is an example - Helium and other elements fuse to form heavier elements

Question 19

From a red giant, what will be formed and how?

Answer 19

A white dwarf, Fusion stops and the star will contract to form a white dwarf

Question 20

From a white dwarf, what will be formed and how?

Answer 20

A black dwarf, Eventually no more light is emitted and the star becomes a black dwarf

Question 21

After a star runs out of hydrogen, what happens will depend on the stars size, If the main sequence star has a high mass, what is formed and how?

Answer 21

A red supergiant, Stars much larger than the sun will swell to become a red supergiant, which continues to collapse

Question 22

What happens when the star explodes?

Answer 22

It explodes in a supernova, the outer layer is thrown into space while the core is left as a neutron star - if it is large enough, it can form a black hole

Question 23

How are chemical elements formed?

Answer 23

By the fusion processes in stars - the nuclei of lighter elements fuse to form the nuclei of heavier elements releasing large amounts of energy

Question 24

How is the solar system formed?

Answer 24

The sun forms at the centre of gas and rock. It’s kinetic energy then allows the gas to escape, leaving rocks to orbit it. The sun evaporates ice.

Rocky planets form near the sun and planets with gas form further away

Question 25

What is nuclear fission?

Answer 25

The splitting of an atomic nucleus