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GCSE Physics > Unit 2: 6 - Radioacitivty > Flashcards

Unit 2: 6 - Radioacitivty Flashcards

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0
Q

How does a radioactive substance become stable?

A

By emitting radiation, making the nuclei stable.

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1
Q

What is a radioactive substance?

A

A substance which contains unstable nuclei.

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2
Q

How do we predict or influence the radioactive decay of a substance?

A

We can’t. It is completely random.

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3
Q

What is background radiation?

A

The radiation that we naturally come into contact with in our daily lives. It can be from rock, space (cosmic radiation), power stations, food, and a lot more.

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4
Q

How does radon enter the body?

A

Through the lungs, as it is a gas.

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5
Q

What is an atom made up of?

A

A nucleus composed of protons and neutrons, orbited by electrons. There is a lot of empty space.

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6
Q

What is the natural process of a radioactive substance becoming stable?

A

Radioactive decay

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7
Q

What was the name of the experiment used to discover the positive charge of the nucleus? Who did it? What did it consist of? What were the results?

A

Alpha particle scattering. By Rutherford, Geiger and Marsden. Alpha particles were fired at thin gold foil. Most particles went straight through, showing that the atom was mostly empty space. Some rebounded through very large angles, suggesting the nucleus has a large mass and a very large positive charge. (Some deflected through small angles, showing that the nucleus had a positive charge)

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8
Q

What change is there in the nucleus from alpha decay?

A

The nucleus loses 2 protons and 2 neutrons

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9
Q

What change is there is there in the nucleus from beta decay?

A

A neutron in the nucleus changes into a proton and an electron.
neutron (0) -> proton (+1) + electron (-1)

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10
Q

What is emitted from alpha decay?

A

2 protons and 2 neutrons as an alpha particle (a positive helium ion with no electrons)

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11
Q

What is emitted in a beta particle?

A

An electron

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12
Q

What is the relative masses and charge of each part of an atom?

A

Proton 1 +1
Neutron 1 0
Electron 0.0005 (1/2000th) -1

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13
Q

A charged atom is called an ____

A

Ion

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14
Q

Atoms with different numbers of neutrons are ____

A

Isotopes

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15
Q

What is the relative charge of an alpha particle?

A

+2 as it has 2 protons and no electrons.

16
Q

What is the relative charge of a beta particle?

A

-1 as it is just one electron.

17
Q

What does carbon-14 become when it emits a beta particle? Explain.

A

It loses one neutron and becomes an electron and a proton. The mass number stays the same, but it becomes nitrogen.

18
Q

What deflects alpha and why?

A

Magnetic and electric fields as they have a positive charge.

19
Q

What is the order of least->most ionising?

A

Gamma>Beta>Alpha

20
Q

What is order of penetration from least->most?

A

Alpha (stopped with paper) > Beta (Stopped with an aluminium sheet) > Gamma (Stopped with lead or lots of concrete)

21
Q

What are the problems in life forms with ionising?

A

Particles knock electrons off atoms which can join onto others, damaging the molecule. DNA can be mutated which will reproduce, and makes cancerous tumours.

22
Q

Why are alpha particles least penetrating?

A

They are large so they have lots of collisions.

23
Q

Why are beta particles more ionising?

A

They are smaller and and move a lot faster.

24
Q

Why is gamma most penetrating?

A

As it is an electromagnetic wave, it can travel a long way and very quickly before collision.

25
Q

How do we measure radioactivity?

A

We measure the count rate

26
Q

What is half-life?

A

Half life is the measure of how quickly the radioactivity count decreases to half of its original value. Or we can define it as the time it takes for the unstable nuclei to halve.

27
Q

What source is used in smoke alarms?

A

An alpha source, americium-238

28
Q

What source would be used for thickness monitoring in metal foil?

A

Beta

29
Q

What sources would be used as tracers in medicine? And why?

A

Beta and gamma. They are most penetrating and least ionising.

30
Q

What is radioactive dating?

A

It is a technique used to find the age of ancient material. Uranium dating is used in igneous rocks and carbon dating is used in wood and other organic material.

GCSE Physics (17 decks)

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