P20: Energy from the Nucleus Flashcards Preview

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Flashcards in P20: Energy from the Nucleus Deck (38)
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1
Q

Nuclear Fission

A

The process in which certain nuclei (uranium-235 and plutonium 239) split into two ‘fragment’ nuclei as a result of absorbing a neutron, releasing energy and two or three neutrons as a result. (chain reaction).

2
Q

Fission Neutrons

A

Neutrons released during fission, which travel at high speed and also catalyse other Fission Reactions.

3
Q

What three things are produced by Nuclear Fission?

A

> Fragment Nuclei
Fission Neutrons: 2-3.
Energy in the form of radiation, and the kinetic energy of the fission neutrons and fragment nuclei.

4
Q

Nuclear Fission Reactor

A

> A reactor that releases energy steadily due to the fission of a suitable isotope such as Uranium-235.
This isotope is suitable because exactly one Fission Neutron from each reaction goes on to catalyse another reaction, keeping the rate of energy production steady.

5
Q

Features of the inside of a Nuclear Reactor

A

> Water is added as a moderator (to slow down the uranium atoms so that they can cause further fission) and a coolant (to absorb kinetic energy from the neutrons and feel rods).
Control Rods: Absorb surplus neutrons (keeps the chain reaction under control).
Reactor Core: Made of thick steel to withstand high temps and pressures. Surrounded by concrete shield to absorb any escaping radiation.

6
Q

Fission

A

Splitting.

7
Q

Fusion

A

Joining.

8
Q

Nuclear Fusion

A

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

9
Q

Fusion of Hydrogen -> Helium

A
  1. Two protons (hydrogen nuclei), collide and react to form ‘Heavy Hydrogen’ (2/1 H).
  2. 2 Protons collide with 2 of these Hydrogens, and turn them into heavier nuclei.
  3. The two heavier nuclei collide to form 4/2 He.
  4. The energy produced at every stage is carried away as kinetic energy.
10
Q

Plasma in a Fusion Reactor

A

> Plasma is heated by passing a large electric current through it.
It is contained by a magnetic field so that it doesn’t touch the reactor walls, which would make it go cold.
If the fusion worked, it would create more energy than it takes to heat the plasma.

11
Q

Problems of Fusion Reactors.

A

> Plasma has to be very hot to be able to overcome the repulsion force between two positive nuclei.
Not yet developed.

12
Q

Positives of Fusion Reactors.

A

> Fuel for fusion is Heavy Hydrogen- abundant in sea water.
Reaction product, helium, is non-reactive and harmless.
Much better than fission reactors.

13
Q

Sources of Background Radiation

A
> Cosmic Rays
> Food and Drink
> Medical Treatments (e.g X-rays)
> Air Travel
> Ground and Buildings
> Natural Radioactivity in the Air.
> Nuclear weapons Testing.
> Nuclear Power.
14
Q

Radon Gas

A

> Seeps through the ground from radioactive rocks buried deep underground.
Emits alpha particles, hazardous if breathed in.
Can seep into buildings etc. in areas where it is abundant.
Combated with special suction pumps underground.

15
Q

Effect of Alpha radiation from a source outside the body.

A

Very dangerous- Affects all surrounding tissue.

16
Q

Effect of Alpha radiation from a source inside the body.

A

Possible Danger- absorbed by skin, can damage skin + retina cells.

17
Q

Effect of Beta and Gamma Radiation from a source inside or outside of the body.

A

Dangerous- Can reach cells throughout the body without having to be ingested.

18
Q

How long ago did the Big Bang take place?

A

13 Billion years ago.

19
Q

How has the universe changed since the big bang?

A

> It began as a hot glowing ball of radiation and matter.

> Now, it is cold and dark except for the hot spots caused by stars.

20
Q

Features of the Dark Age of the Universe.

A

> As the universe expanded, it became transparent as radiation passed through the empty space between its atoms.
Microwave Background Radiation was released at this stage.
The universe was a dark, patchy cloud of hydrogen and helium.
Slowly, the denser parts of the universe began to attract the surrounding matter, and the universe became even more patchy.
Eventually, gravity drew these clumps into galaxies, and the stars lit up the universe.

21
Q

What do stars form out of?

A

Clouds of Dust and Gas

22
Q

Protostar

A

> The Concentration of dust clouds and gas in space that goes on to form a star.
The dust and gas are drawn together by their own gravitational force.

23
Q

What happens if a Protostar gets hot enough?

A

> The nuclei of hydrogen and all of the light elements fuse together, releasing energy which causes it to get hotter and brighter- a star is born.

24
Q

What happens to Protostars that don’t get hot enough for fusion to take place?

A

They may be attracted by another, larger protostar’s gravitational force and become planets.

25
Q

Main Sequence Stars

A

> Main stage in a star’s lifecycle.
Energy released from fusion allows more fusion to take place.
Radiation flows out steadily.
Stable- the forces within it are balanced.

26
Q

What forces keep a main sequence star balanced?

A

> Gravity makes the star contract.

> The radiation from the core makes the star expand.

27
Q

Red Giant

A

> A main sequence star smaller than our sun that has swelled out, cooled down and turned red.
At this stage the light elements start to fuse to create heavier elements.

28
Q

What happens when a Red Giant runs out of light elements for fusion?

A

> No more radiation is released.
Because of the star’s own gravity, it collapses in on itself.
As it collapses, it heats up and turns from red- yellow- white. (White Dwarf)

29
Q

White dwarf

A

A star that has collapsed after the Red Giant stage and has become much hotter and denser that it was.

30
Q

Black dwarf

A

A star that has faded out and gone cold.

31
Q

Lifecycle of a small star

A
Protostar
Main Sequence
Red Giant
White Dwarf
Black Dwarf
32
Q

Red Supergiant

A

> A star much larger than the sun will swell out after the main sequence stage to become a red supergiant before it collapses.
This happens because it has run out of light elements to use in fusion.

33
Q

What happens when a Red Supergiant collapses?

A

> The matter surrounding the core compresses the core more and more.
Then the compression suddenly reverses in a supernova.

34
Q

Supernova

A

The explosion of a massive star after fusion in its core stops and the matter surrounding the core collapses onto the core and rebounds.

35
Q

What happens after a supernova.

A

> The core of the star is compressed until it becomes a neutron star (made entirely of neutrons).
If the stare is big enough, it becomes a black hole instead.

36
Q

Black Hole

A

The extremely compressed core of a star that has so much mass that nothing, not even light, can escape its gravitational field.

37
Q

How are light elements formed?

A

In fusion in a star’s core.
When a star becomes a red giant it starts to fuse lighter elements up to iron.
Anything larger than iron can’t be formed in this process because it requires too much energy.

38
Q

How are heavy elements formed?

A

> When a massive star collapses and then explodes as a supernova.
The enormous force first fuses them and then propels them into space.
Because planets form out of the elements found around a newly formed star, planets contain all of the known elements.