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(A) Physics > P6 > Flashcards

P6 Flashcards

1
Q

What are subatomic particles

A

Particles found inside atoms, like neutrons protons and ekectrons

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2
Q

What are isotopes

A

Atoms of the same elements with different numbers of neutrons

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3
Q

What are the mass and charges of neutrons protons and electons

A

Charge:
E = -1
P = +1
N = 0

Mass
E = 1/1835 (taken as 0)
P = 1
N = 1

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4
Q

What does the mass number of an atom show

A

The number of protons and neutrons

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5
Q

What does the atomic number show

A

Number of protons in the nucleus
Or electrons in the outer shell

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6
Q

What happens if a nuclei is unstable

A

It xan emit radiation

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7
Q

What does it mean if a nuclei is unstable

A

A nucleus that decays by emitting radiation or by fission

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8
Q

Why do the nuclei of atoms decay

A

If a change in the atoms configuration it will become unstable (as it is no longer balanced)
And it will attempt to become stable by decaying

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9
Q

What are the 5 main types of Radiation and their symbols

A

Alpha (a)
Beta (β + or -)
Gamma (y)
Neutron decay

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10
Q

What is an alpha particle

A

A charged particle with no electrons
It is the nucleus of a helium atom
(+2 charge and a mass of 4)

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11
Q

What is a beta minus particle

A

A high speed energy electron

It has a charge of -1 and a mass of 0 (1/1835)

It is released from the nucleus when a neutron transforms into a proton

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12
Q

What is a beta plus particle

A

A particle with a +1 charge and a mass of 0 (1/1835)

It is a high speed POSITRON
(Same characteristics as an electron but positive)

It is released from the nucleus when a proton transforms into a neutron

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13
Q

What is gamma radiation

A

High energy + high frequency electromagnetic wave

It has a mass of 0 and a charge of 0

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14
Q

What is penetrating power

A

The ability to travel through a material

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15
Q

What is the ionising power, range and penetration power of, alpha, beta and gamma

A

Alpha - high ionising power, short range (a few cm) and small penetrating power (stopped by a few sheets of paper)

Beta - Moderate ionising power, medium range (a few m) and a low penetrating power (stoped by a few mm of aluminium)

Gamma - little ioninsing power, far range (a few km) and a great penetrating power (a few m of lead or concrete)

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16
Q

How can radiation be detected

A

Using a geiger counter
This device ‘clicks’ when radiation enters it, as the radiation ionised the gas inside the tube

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17
Q

What happens in alpha decay

A

The atomic number decreases by 4
The mass number decreases by 2

E.g 240 Pu → 236 U + 4 He
94 92 2

Helium nucleus is limited

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18
Q

What happens in beta - decay

A

A neutron becomes a proton and an electron is emitted
The mass number stays the same, but the atomic number increases by 1

E.g

218 Po → 218 At + 0 e
84 85 -1

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19
Q

What happens in beta + decay

A

Opposite of beta -
A proton transforms into a neutron and releases a positron

Mass number stays the same
Atomic number decreases by 1

218 Po → 218 Bi + 0 β
84 83 +1

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20
Q

What happens in gamma decay

A

There is no change in the atom / isotope as gamma radiation has no mass or charge

It is normally emitted WITH alpha or beta particles

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21
Q

What happens in neutron decay

A

A neutron is emitted, so the mass decreases by 1
The charge remains the same

5 He → 4 He + 1 n
2 2 0

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22
Q

Is the way a material decays uniform

A

No it is random

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23
Q

What can a geiger counter measure

A

The radiation emitted per second (called activity)

It is measured in becquerels

1 becquerel = 1 count (wave or particle) per minute

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24
Q

What is half life

A

The time taken for the activity to halve in a material

Half life is measured in time and shows how wuickly a material decays

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25
Q

How are graphs used to calculate half life

A

Time is plotted (x axis) against activity

When the activity is halved we can read down to see how long it took

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26
Q

what is net decline

A

The ratio showing the ratio of final to initial activity

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27
Q

What is the net decline after two half lives

A

1:4 - it has halved twice (it is a quarter its original size)

28
Q

How are electrons arranged

A

In fixed energy levels around the nucleus of an atom known as electrong shells

29
Q

What does the photon model show

A

How electromagnetic radiation is emitted and absorbed as packets of enegy called photons
The energy of each photon is proportional to its frequency

30
Q

What happens when photons excite electrons

A

When photons have enough energy electrons can be excited
This causes the electron to move up an energy level

31
Q

Other than collisions with photons how can electrons be excited

A

Passing an electric current through electrons in a gas

32
Q

What happens when electrons move from a higher energy level to a lower one

A

Radiation is emitted
The frequency of the radiation depends on the difference in energy levels

The change in energy levels can be between multiple levels not just one

33
Q

How do absorption spectrums work and what do they show

A

When light of all frequencies is passed through hydrogen gas some frequencies are absorbed.

The spectrum shows a set of frequencies of radiation absorbed by an atom when excited electrons move to higher energy levels

34
Q

Which photons (pieces of the electromagnetic spectrum) have enough energy to ionise atoms

A

Ultraviolet, X-ray and Gamma

35
Q

What does an emission spectrum shown

A

Shows a set frequency of radiation emitted when excited ekctrins move to lower energy levels

36
Q

What is contamination (radiation)

A

When the radioactive material is inside the body or skin
(Or an object)

37
Q

What is irradiation

A

Being exposed to radiation from an external source

38
Q

What is background radiation

A

A measure of the level of ionising radiation present in the environment

39
Q

What happens when you move away from a source of radiation that is irradiating

A

It no longer effects you

40
Q

When is irradiation used

A

Used in x-rays
Foods are irradiated to improve their shelf life

41
Q

Irradiation vs contamination

A

Irradiation :
Object exposed to radiation outside the body
Can cause cancer
Exposure stops when source is removed
Object doesnt become radioactive

Contamination
Object exposed to a source of radiation in or around the body
Can cause cancer
The object is radioactive as long as its contaminated
Difficult to remove contamination

42
Q

What are the medical uses of irradiation

A

Gamma knife → moveable ray of gamma radiation that is focused onto tumors
This kills cancerous cells or inhibits their growth

Can be used to sterilize equipment (kills microorganisms e.g bacteria)

43
Q

What are the medical uses of contamination

A

Radioactive tracers are injected into patients
These are absorbed by organs and through the releasing of gamma radiation show images of organs

44
Q

Why is gamma radiation used for radioactive tracers

A

They have a high penetrating power so less radiation would be absorbed by the patient

45
Q

Why are alpha particles not used for radioactive tracers

A

They have a low penetrating power so the patient would absorb the radiation
(Causing cancer)

46
Q

Why are radiotracers with a short half life chosen

A

To minimise the time of exposure to radiation
The radiotracer would have to have a long enough half life to be effective

47
Q

What is the conservation of mass

A

Mass is conserved in physical and chemical reactions

48
Q

What is nuclear fission

A

A nuclear reaction where mass is not conserved
Nuclear fission reactions are used to generate energy in nuclear reactors

When a neutron hits a nucleus the nuclei split into two smaller nuclei, which also release neutrons (release 2 or 3 between them)
These neutrons then hit other nuclei, which release more neutrons

Causing a chain of reactions

49
Q

How are nuclear fission reactions controlled

A

Control rods are made of a material that can absorb neutrons
This prevents the chain reaction from continuing

50
Q

How / why are neutrons slowed down during nuclear fission reactions

A

The neutrons are emitted at high speeds, and slowed down by moderators which absorb energy from the neutrons

This is done so the control rods can absorb neutrons faster

51
Q

What does it mean if a material is fissionable + examole

A

Uranium - 235 is fissionable

This means that it can split easily

52
Q

What are the benefits of nuclear fission reactions

A

1g of uranium is equal to 3000kg of coal in energy

53
Q

What are the dangers of using nuclear fission reactions

A

Long half lives of radioactive waste (100+ years some over 200,000)
Chernobyl disaster, making land unusable due to radioactive waste
Radioactive waste emits beta and alpha particles

54
Q

How is radiation prevented from entering the environment during nuclear fission reactions

A

The reactor is sealed in a metal container, encased in concrete and then fused in glass and sealed in a metal casing

This prevents all types of radiation escaping to the environment

55
Q

What is mass energy equivalence

A

The fact that during nuclear reactions not all mass is conserved
Some is converted to energy

56
Q

What famous equation did Einstein make relating to mass energy equivalence

A

Energy = mass × speed of light²
E=mc²

This equation shows the energy released when an objects mass is fully converted into energy

57
Q

What is the speed of light

A

3×10⁸ m/s

58
Q

What is nuclear fusion

A

The joining of two lighter nuclei to form a larger nucleus which releases energy

59
Q

How does the size of a nuclei depend on what nuclear reaction will occur to it

A

Larger nuclei split when hit with electrons
Smaller nuclei fuse to form a more stable nuclei

60
Q

What atoms are used for most fusion reactions

A

Isotopes of hydrogen
Two protons are fused to make hydrogen-2 (deuterium)
Hydrogen-3 is formed by fusing deuterium
(Also forms hydrogen)

61
Q

What do hydrogen-2 and hydrogen-3 fuse to form

A

They join to form a helium atom and a neutron

62
Q

What is the heaviest nucleus of an element that can be made through fusion

A

Iron
It is formed in a supernova

63
Q

Why are fusion reactions possible in the sun

A

High temperatures keep the nuclei moving at high speeds
High pressures keep the nuclei close enough to fuse

64
Q

Why is energy released during nuclear fusion

A

Energy is released by radiation
Calculated using e=mc²

65
Q

Why is hydrogen a good fuel for nuclear fusion

A

It is the most abundant element on the earth

66
Q

Why does nuclear fusion not create radioactive waste

A

The nucleus formed is stable

(A) Physics (10 decks)

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