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GCSE Physics > P7 - Radioactivity - Complete > Flashcards

P7 - Radioactivity - Complete Flashcards

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1
Q

Why do radioactive substances emit radiation?

A

In order to stabilise their nuclei

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2
Q

What is the most penetrating type of radiation?

A

Gamma radiation

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3
Q

What particle did Ernest Rutherford fire at foil o discover the idea of positive nuclei?

A

Alpha particles

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4
Q

What charge is alpha radiation?

A

Positive

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5
Q

What is radioactive decay and when does is happen?

A

Radioactive decay is when a radioactive substance’s nucleus emits radiation in order to become stable, it is a random even that occurs without stimulation to the nucleus

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6
Q

What are the three main types of radiation?

A

Alpha, beta and gamma

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7
Q

Why was the experiment to fire alpha particles at the metal foil in a vacuum chamber?

A

Because otherwise the air particles would absorb the radiation

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8
Q

Why could the plum pudding model still not make sense after Rutherford’s experiments?

A

As it would be impossible for the particles to rebound at the same angles that some of them had if it was true

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9
Q

What does and electron moving shell cause?

A

A small burst of radiation called a photon. This burst is equal to the energy change caused by the jump

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10
Q

What changes is alpha decay?

A

The number of protons and neutrons in the nucleus

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11
Q

What changes in beta decay?

A

The number of protons in the nucleus

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12
Q

What is the mass number?

A

How many protons + neutrons there are in an atom. It is represented by the letter A

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13
Q

What is the atomic number?

A

Otherwise known as the proton number, it is the number of protons in a nucleus. It has the letter Z

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14
Q

What is an isotope?

A

An atom of the same element with a different number of neutrons

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15
Q

What makes up an alpha particle?

A

Two protons and two neutrons. It is identical to the helium nucleus

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16
Q

What happens when an unstable nucleus emits an alpha particle?

A

Its mass number goes down by 4 and its charge decreases by 2

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17
Q

What makes up a beta particle and how is it made?

A

An electron makes it up, and it is created by a neutron separating into an electron and a proton in the atom’s nucleus

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18
Q

What happens when an unstable nucleus emits a beta particle?

A

The atomic number of the nucleus goes up by 1, its mass decreases by 1/2000th, and the charge of the nucleus is increased, as it has gained a new proton

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19
Q

What is gamma emission?

A

Gamma emission is uncharged electromagnetic radiation from the nucleus of an atom. As it has no charge and no mass, it does not change the atom in any way

20
Q

What can cause neutron emission?

A

Neutron emission can be caused by alpha particles colliding with unstable nuclei - causing them to become even more unstable and so they emit a neutron. Because neutrons are uncharged, they can pass through

21
Q

Why are normal particles not radioactive?

A

Because the force inside the nucleus, called strong nuclear force, is strong enough to resist the repulsion between the protons and can keep the neutrons from moving away from the nucleus

22
Q

What can stop alpha radiation?

A

A piece of paper

23
Q

What can stop beta radiation?

A

An aluminium sheet of about a 5mm thickness, and a lead sheet about 2-3mm thick

24
Q

What can stop gamma radiation?

A

Concrete that is more than 1m thick and a several cm thick lead sheet

25
Q

What is alpha radiation’s range through the air?

A

About 5cm

26
Q

What is beta radiation’s range through the air?

A

About 1m

27
Q

What is gamma radiation’s range through the air?

A

Unlimited - it can spread out through the air without being absorbed

28
Q

What can radiation do to other atoms?

A

It can knock their electrons out of orbit: causing them to become charged ions. They are said to have been irradiated

29
Q

What does ionisation do to a living cell?

A

It can kill it or harm its genes. If the genes are harmed but the cell still replicates, these genes can be passed on

30
Q

What is the most dangerous type of radiation in the body?

A

Alpha radiation, as its ionising power is much greater than that of the other two types

31
Q

What safety measures of workers take when handling radiation?

A

Keeping as far away as possible from the source, spending as little time as possible in risky areas, and shielding themselves by using thick concrete barriers and/or thick lead plates

32
Q

When is radiation used?

A

In automatic thickness machines, where beta particles are used to make sure the sickness of the aluminium is correct, and in smoke alarms to ionise the air between parts of the circuit so that is the current across that part drops - due to smoke absorbing the ions - and the alarm sounds

33
Q

What is activity in relation to radioactivity and what is its measurement?

A

Activity is the amount of unstable atoms in the source that decay per second. Its symbol is the Becquerel (Bq), which is 1 decay per second. As the atoms decay, they become stable, and so the activity decreases

34
Q

What is the half life of a group of radioactive atoms?

A

The time it takes for half of the atoms to decay - and so the activity to half

35
Q

Give 2 ways nuclear radiation is used in medicine

A

To detect whether a kidney is blocked - they give them a radioactive substance and detect the signals. If the signals go up and then stay there, then the kidney is blocked.
To implant to get rid of cancerous tumours. This works as the radiation kills the tumour and then the substance should decay.
Gamma rays in a narrow beam can be used to kill cancerous tumours.
Gamma cameras can be used to see where a substance is absorbed into in the body. The patient is injected with a radioactive isotope and the camera senses where the radiation is coming from inside the body and uses that data to build up a picture

36
Q

How would you go about choosing an isotope to treat a patient?

A

Decide what type of treatment they need and then match the type of radiation they need with the type of isotope you supply. Then make sure the half life of the radioactive substance is short or long enough to decay before it in itself becomes a problem

37
Q

What is nuclear fission?

A

The splitting of an atom’s nucleus into 2 smaller nuclei, releasing 2 or 3 neutrons and energy

38
Q

What can one fission cause?

A

A chain reaction, as each neutron released from the broken nucleus can cause other nuclei to break

39
Q

What is used to stop chain reactions in nuclear reactors?

A

Control rods to absorb the neutrons that come from the fissioned nuclei and adding unfashionable substances such as Uranium-238.

40
Q

Name 1 fissionable substance.

A

Uranium-235 and Plutonium-239

41
Q

How is fission caused in nuclear reactors?

A

They fire a neutron at high speed at the nucleus of the uranium or plutonium

42
Q

What is nuclear fusion?

A

The forcing together of 2 nuclei that have a relative mass of no more than 55 to form a larger nuclei

43
Q

Where is nuclear fusion taking place constantly?

A

In the centre of the sun and other stars

44
Q

Name 1 positive and 1 negative of nuclear fusion?

A

It is renewable, it could provide millions with energy, its fuel is easy found.
It would also need a lot of energy to activate and the nuclei to be fused would be hard to control

45
Q

How does nuclear fusion in a reactor work?

A

The two nuclei are fired at each other at extremely high speeds. They need to bound together by the strong nuclear force, but have to be fired with enough kinetic energy to overcome the opposing forces of electrostatic repulsion (positive and a positive)

46
Q

What is radon gas and where does it come from?

A

A gas that emits alpha particles and seeps from the ground in some areas

47
Q

What changes might be instigated into future nuclear reactors?

A

Standard design that reduces build time and costs, a longer operating life, more safety features and less effect on the environment

GCSE Physics (17 decks)

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