Energy From The Nuckeus

Question 1

Which fissionable isotopes are used?

Answer 1

Uranium- 235

Plutonium 239

Question 2

What is the most naturally occurring form of uranium?

Answer 2

U-238, which is non fissionable

Question 3

What is enriched uranium?

Answer 3

Uranium which contains 2-3% of fissionable U-235

Question 4

What must happen for fission to occur?

Answer 4

The U- 235 or plutonium 239 nucleus must absorb a neutron. Then the nucleus splits into 2 smaller nuclei. In the process 2 or 3 more neutrons are emitted and energy is released

Question 5

Why is nuclear fission better than burning?

Answer 5

Nuclear fission releases much more energy than burning

Question 6

When does a chain reaction occur in nuclear fission?

Answer 6

When each fission event causes further fission events

Question 7

How is the process of nuclear fission controlled?

Answer 7

Only one fission neutron per fission on average goes onto produce further fission

Question 8

What is nuclear fusion?

Answer 8

The process of forcing 2 nuclei close enough together so they form a single larger nucleus

Question 9

How can cycle at fusion be brought about?

Answer 9

Making 2 light nuclei collide at very high speed

Question 10

Where does fusion occur naturally?

Answer 10

Stars

Question 11

Why must the fusion nuclei by heated to a very high temperature?

Answer 11

To overcome the repulsion of the positive charge and force the nuclei to fuse

Question 12

How are nuclei contained in a fusion reaction?

Answer 12

Contained in a magnetic field

Question 13

What is the biggest source of background radiation

Answer 13

Radon gas which seeps through the ground from radioactive substances in rocks deep underground

Question 14

Why is radon gas a health hazard?

Answer 14

Radon emits alpha particles so is a health hazard if breathed in

Question 15

List other sources of background radiation

Answer 15

Cosmic rays from space, food and drink, air travel and nuclear weapons testing and medical sources eg X-rays

Question 16

How can workers reduce the risk of exposure to nuclear radiation?

Answer 16

Keep away from source of radiation
Spend little time exposed
Shield themselves with concrete or lead

Question 17

Why must radioactive wate be stored securely?

Answer 17

So it does not enter the environment

Question 18

Why is uranium and plutonium chemically removed from used fuel rods?

Answer 18

The substances can be used again

Question 19

When did the Big Bang occur?

Answer 19

13 billion or thousand million years ago

Question 20

What was the universe at first?

Answer 20

A hot glowing ball of radiation

Question 21

What happened in the first few minutes of the Big Bang?

Answer 21

The nuclei of the lightest elements formed

Question 22

As the universe expanded over millions of years what happened?

Answer 22

The temperature fell and uncharged atoms were formed

Question 23

What is nuclear fission?

Answer 23

Is the splitting of an atomic nucleus

Question 24

What happened to the temperature of the universe as it expanded?

Answer 24

It decreased

Question 25

Before galaxies and stars formed what was the universe like?

Answer 25

A dark patchy cloud of hydrogen and helium

Question 26

What happened eventually so that starts were formed?

Answer 26

The dust and gas were pulled together by gravitational attraction to form stars

Question 27

How did stars begin to emit light and radiation?

Answer 27

After the dust and gas was pulled together by gravitational attraction, the resulting heat started off nuclear fusion reactions in stars

Question 28

What is a galaxy?

Answer 28

A very large group of stars held together by their own gravity

Question 29

What is our galaxy called

Answer 29

The Milky Way

Question 30

The distance between neighbouring stars is usually ............ Of times greater than the distance between.......... In our solar system.

Answer 30

Millions | Planets

Question 31

The distance between neighbouring ............ Is usually millions of times greater than the distance between ...... Within a ..........

Answer 31

Galaxies Stars Galaxy

Question 32

How are protostars formed?

Answer 32

Gravitational forces pull clouds of dust and gas together to form a protostar

Question 33

The protostar becomes ........ And the nuclei of hydrogen atoms and other light elements start to ....... Together. Energy is released in the process so the core gets ........... And ..........

Answer 33

Denser Fuse Hotter Brighter

Question 34

Why do stars radiate energy?

Answer 34

Hydrogen fusion in the core

Question 35

Why are stars in the main sequence stage stable?

Answer 35

The inward force of gravity is balanced by the outward force of radiation from the core

Question 36

What happens to a star when it runs out of hydrogen to fuse

Answer 36

It swells cools down and turn red

Question 37

What type of star is the sun?

Answer 37

Red giant

Question 38

What is the sequence that a low mass star will go through?

Answer 38

``` Protostar MSS Red giant White dwarf Black dwarf ```

Question 39

When will a low mass star form a white dwarf?

Answer 39

When fusion stops the star will contract becoming a white dwarf

Question 40

When will a low mass star form a black dwarf?

Answer 40

When no more light is emitted

Question 41

After the main sequence a star much larger than pursue will become a.......

Answer 41

Red supergiant

Question 42

What happens after a star is a red supergiant?

Answer 42

The star explodes in a supernova as the outer layers are thrown out into space?

Question 43

What is the core of the star left after a supernova called

Answer 43

A neutron star

Question 44

When does a neutron star become a black hole?

Answer 44

If it is massive enough

Question 45

Why can no light escape from black hole.

Answer 45

The gravitational field strength is so strong

Question 46

What is the heaviest element formed by fusion in stars

Answer 46

Iron

Question 47

Why are elements heavier than iron only formed in the fink stages of the life of a big star?

Answer 47

The process requires an input of energy

Question 48

What is the presence of heavier elements in the sun and innner planets evidence for.

Answer 48

They were formed from the debris scattered by. Supernova

Question 49

Explain how stars like the Sun are thought to have been formed

Answer 49

Dust and gas or remnepants of

Question 50

Explain how helium is formed in a star

Answer 50

Fusion of hydrogen

Question 51

Explain how atoms of heavy elements were formed s

Answer 51

Fusion of light elements | During a supernova

Question 52

Explain how and when different elements may be distributed throughout the universe

Answer 52

Supernova explosion | At the end of a stars life

Question 53

Explain why scientists believe that the solar system was formed from the material produced when earlier stars exploded

Answer 53

Solar system contains heavy elements | Formed in a supernova

Question 54

De scribe how a massive star bigger than the sun will change at the end of the main stable period

Answer 54

Expands into red giant Explodes to become supernova Dense neutron star left behind If massive enough forms a black Hole

Question 55

What is meant by the term black hole?

Answer 55

Matter with such high gravitational strength | Light is pulled in

Question 56

Describe what happens to the sun as the hydrogen is used up until the sun dies u

Answer 56

fusion decreases or stops •        collapses rapidly causing the (core) temperature to rise •        (inward) gravitational forces no longer balance (outward) pressure •        expands •        and becomes a red giant •        it cools •        then becomes a white dwarf

Question 57

Explain how our sun formed from the time when There was just dust and gas up to now when it is in the main sequence

Answer 57

``` Dust and gas pulled together Formed when it is hot enough Hydrogen fuses Releasing energy Which causes expansion Gravity is balanced to radiation pressure ```