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P6 Flashcards

(66 cards)

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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
How are graphs used to calculate half life
Time is plotted (x axis) against activity When the activity is halved we can read down to see how long it took
26
what is net decline
The ratio showing the ratio of final to initial activity
27
What is the net decline after two half lives
1:4 - it has halved twice (it is a quarter its original size)
28
How are electrons arranged
In fixed energy levels around the nucleus of an atom known as electrong shells
29
What does the photon model show
How electromagnetic radiation is emitted and absorbed as packets of enegy called photons The energy of each photon is proportional to its frequency
30
What happens when photons excite electrons
When photons have enough energy electrons can be excited This causes the electron to move up an energy level
31
Other than collisions with photons how can electrons be excited
Passing an electric current through electrons in a gas
32
What happens when electrons move from a higher energy level to a lower one
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
How do absorption spectrums work and what do they show
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
Which photons (pieces of the electromagnetic spectrum) have enough energy to ionise atoms
Ultraviolet, X-ray and Gamma
35
What does an emission spectrum shown
Shows a set frequency of radiation emitted when excited ekctrins move to lower energy levels
36
What is contamination (radiation)
When the radioactive material is inside the body or skin (Or an object)
37
What is irradiation
Being exposed to radiation from an external source
38
What is background radiation
A measure of the level of ionising radiation present in the environment
39
What happens when you move away from a source of radiation that is irradiating
It no longer effects you
40
When is irradiation used
Used in x-rays Foods are irradiated to improve their shelf life
41
Irradiation vs contamination
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
What are the medical uses of irradiation
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
What are the medical uses of contamination
Radioactive tracers are injected into patients These are absorbed by organs and through the releasing of gamma radiation show images of organs
44
Why is gamma radiation used for radioactive tracers
They have a high penetrating power so less radiation would be absorbed by the patient
45
Why are alpha particles not used for radioactive tracers
They have a low penetrating power so the patient would absorb the radiation (Causing cancer)
46
Why are radiotracers with a short half life chosen
To minimise the time of exposure to radiation The radiotracer would have to have a long enough half life to be effective
47
What is the conservation of mass
Mass is conserved in physical and chemical reactions
48
What is nuclear fission
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
How are nuclear fission reactions controlled
Control rods are made of a material that can absorb neutrons This prevents the chain reaction from continuing
50
How / why are neutrons slowed down during nuclear fission reactions
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
What does it mean if a material is fissionable + examole
Uranium - 235 is fissionable This means that it can split easily
52
What are the benefits of nuclear fission reactions
1g of uranium is equal to 3000kg of coal in energy
53
What are the dangers of using nuclear fission reactions
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
How is radiation prevented from entering the environment during nuclear fission reactions
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
What is mass energy equivalence
The fact that during nuclear reactions not all mass is conserved Some is converted to energy
56
What famous equation did Einstein make relating to mass energy equivalence
Energy = mass × speed of light² E=mc² This equation shows the energy released when an objects mass is fully converted into energy
57
What is the speed of light
3×10⁸ m/s
58
What is nuclear fusion
The joining of two lighter nuclei to form a larger nucleus which releases energy
59
How does the size of a nuclei depend on what nuclear reaction will occur to it
Larger nuclei split when hit with electrons Smaller nuclei fuse to form a more stable nuclei
60
What atoms are used for most fusion reactions
Isotopes of hydrogen Two protons are fused to make hydrogen-2 (deuterium) Hydrogen-3 is formed by fusing deuterium (Also forms hydrogen)
61
What do hydrogen-2 and hydrogen-3 fuse to form
They join to form a helium atom and a neutron
62
What is the heaviest nucleus of an element that can be made through fusion
Iron It is formed in a supernova
63
Why are fusion reactions possible in the sun
High temperatures keep the nuclei moving at high speeds High pressures keep the nuclei close enough to fuse
64
Why is energy released during nuclear fusion
Energy is released by radiation Calculated using e=mc²
65
Why is hydrogen a good fuel for nuclear fusion
It is the most abundant element on the earth
66
Why does nuclear fusion not create radioactive waste
The nucleus formed is stable

Physics (10 decks)

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