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GCSE Physics > Topic 6 > Flashcards

Topic 6 Flashcards

Done except for a few specpoints

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1
Q

6.1
Describe an atom (include where mass is concentrated)

A

-Positive nucleus that has protons and neutrons
-Most mass in nucleus
-Surrounded by negatively charged electrons on energy levels

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2
Q

6.1 6.2
a) State the radius of an atom (include units)
b) State the radius of a nucleus (include units)
c) How many times bigger is the atom than the nucleus inside it?

A

a) ~ 1×10^-10 m
b) ~1×10^-15 m
c) 100,000 times

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3
Q

6.3 6.4
Define the term isotope

A

Atom with same number of protons but different number of neutrons

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4
Q

6.5
State the relative masses and charges of the 3 main subatomic particles

A

CHARGES:
p: +1
n: 0
e: -1
MASSES:
p: 1
n: 1
e: 0.0005

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5
Q

6.6
Why is the overall charge of an atom neutral?

A

-Equal number of protons and electrons
-Cancel out

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6
Q

6.7
In an atom, how do electrons orbit around the nucleus?

A

In energy levels, at different set distances from the nucleus & each other

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7
Q

6.8
Describe what happens when an atom absorbs and then emits radiation. What type of radiation is emitted?

A

-Absorbs: electron gets excited, moves up energy level
-Emits: electron loses energy, jumps down energy level
-EM radiation

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8
Q

6.9
How do atoms form ions?

A

-Lose electrons to become positive cations
-Gain electrons to become negative anions

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9
Q

6.10
Where is alpha, beta minus, beta plus, gamma rays and neutron radiation emitted from?

A

Unstable nuclei in a random process

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10
Q

6.11
Name 4 types of ionising radiation

A

-Alpha
-Beta minus
-Beta plus
-Gamma

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11
Q

6.11
Define the term ionising radiation

A

Has enough energy to ionise atom (remove electrons from it)

Explanation (don’t need to know): Electron given more energy than needed to reach outermost shell, so will transfer elsewhere and atoms becomes ion

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12
Q

6.12
What is meant by background radiation?

A

-Ionising radiation around us all the time
-Caused by number of sources
-Some = naturally occurring
-Some = human activities

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13
Q

6.12
How much of background radiation is made up of radon gas?

A

49%

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14
Q

6.13
Describe how radon gas is produced

A

Unstable uranium in rocks underground decaying and emitting radiation

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15
Q

6.13
State the origins of background radiation

A

-Radon gas
-Medical
-Ground & buildings
-Cosmic rays
-Food & drink
-Nuclear and other

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16
Q

Why can radioactive substances decay so easily?

A

They are unstable

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17
Q

What causes a nucleus to be unstable?

A

Having a higher mass

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18
Q

What is released in the process of a nucleus becoming more stable?

A

Radiation

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19
Q

6.14
Give 2 ways we can detect/measure radioactivity

A

-Geiger-Muller tube
-Photographic film

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20
Q

6.15
a) What is an alpha particle equivalent to?
b) What is a beta particle?
c) What is a gamma ray?

A

a) Helium nucleus
b) Electron emitted from nucleus (neutron breaks down into proton & electron but proton stays)
c) EM radiation

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21
Q

6.16
Rank the ionising radiations in terms of how ionising and penetrating they are

A

-IONISING most to least:
Alpha, Beta, Gamma
-PENETRATING most to least:
Gamma, Beta, Alpha

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22
Q

6.16
What affects the amount of ionising power of the radiation?

A

Mass & charge

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23
Q

6.16
State the materials that stop each radioactive decay

A

-Paper stops alpha
-Aluminium stops beta
-Lead (almost) stops gamma

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24
Q

6.17
Name and draw the first 4 atomic models and who created them

A

-DALTON’S SPHERE (JOHN DALTON)
-A sphere

-PLUM PUDDING MODEL (J.J. THOMSON)
https://www.ecosia.org/images?q=plum%20pudding%20model#id=2D8F9F323DE56D626F3F876EC7F7009BD7654A21

-NUCLEAR MODEL (ERNEST RUTHERFORD)
Nucleus (as a ball) with electrons orbiting around it RANDOMLY (not on shells)

-ELECTRON SHELL MODEL (NIELS BOHR)
Nucleus in middle with protons and neutrons. Electrons in fixed orbits around nucleus

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25
Q

6.17
Explain why the atomic model has changed over time (include dates)

A

-1803 Dalton
-1897 J.J Thomson discovered electrons with use of cathode ray tube
-1911 Rutherford fired alpha particles at thin gold foil. Some detected by detectors, others reflected, some deflected so came to conclusion of tiny, heavy, positive nucleus
-1913 If Rutherford’s model was true, atom would have collapsed so Niels Bohr came up with electron shells

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26
Q

6.17
Explain what Rutherford suggested the atom was composed of

A

-Mostly empty space
-Positive, tiny, heavy nucleus

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27
Q

6.18
Describe the process of Beta minus decay

A

-Neutron -> proton + electron
-Beta particle (electron -> negative charge) emitted

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28
Q

6.19
Describe the process of Beta plus decay

A

-Proton becomes neutron + positron
-Positron (positive charge) emitted

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29
Q

6.19
State the relative mass and charge of a positron

A

Mass = 0.0005
Charge = +1
(Basically a positive electron)

30
Q

6.20
Describe the effects of each radioactive decay on an atom

A

α:
Mass = Decreases by 4
Atomic number = Decreases by 2

β-:
Mass = Same
Atomic number = Increases by 1

β+:
Mass = Same
Atomic number = Decrease by 1

ɣ:
Mass = Same
Atomic number = Same

neutron emission:
Mass = Decreases by 1
Atomic number = Same

31
Q

6.21
What happens to the atom when it emits a high frequency gamma wave?

A

Atom remains same but loses some energy

32
Q

6.22
State the equation symbols for:
-Alpha particle
-Electron
-Positron
-Gamma ray

A

4 OR 4
α He
2 2

0 OR 0
β e
-1 -1

0 OR 0
β e
+1 +1

0
ɣ
0

33
Q

6.22
Radium-226 emits an alpha particle. What is the other product?

A

226 4 222
Ra –> He + Rn
88 2 86

34
Q

6.22
Uranium 238,
238
U
92,
emits an alpha particle to become what nucleus?

A

238 4 234
U –> α + Th
92 2 90

35
Q

6.23
What does the ‘activity of a substance’ mean?

A

The number of radioactive decays per second

36
Q

6.23
Describe how the activity of a radioactive source decreases over a period of time

A

It halves each time

37
Q

6.24
State the unit used for the activity of a radioactive isotope

A

Becquerel, Bq

38
Q

6.25
Define the term half-life

A

t taken for 1/2 of unstable nuclei in sample of radioactive isotopes to decay

39
Q

6.26
What is radioactive decay? Can it be predicted? How can half-life be useful here?

A

-Unstable nuc emitting radiation to become stable
-No. It is a random process
-Predict activity of large amounts of nuclei

40
Q

6.27
Describe how to work out the half life of an isotope from a graph of its activity over time

A

-Starting point = 0 minutes/years etc. Say activity is 100
-Go down to activity of 50 and see how long it has taken to get there
-Keep doing
-That’s the half life

41
Q

6.27
A radioactive isotope has a half-life of 15 days and an initial count-rate of 200 counts per second. Determine the count rate after 45 days

A

Start = 200
15 days = 100
30 days = 50
45 days = 25

25 counts per second

42
Q

6.28P
State 6 uses of radiation

A

-Killing micro-organisms in food (micro-organisms cause food to decompose -> food poisoning. Makes safer to eat)
-Sterilising equipment
-Detecting leaks
-Diagnosing cancer
-Checking paper thickness
-Smoke alarms

43
Q

6.28P
Give a short description of how radiation (include which type) can be used to sterilise equipment

A

-Equipment sealed in bag & irradiated with gamma rays to kill micro-organisms
-Alternative to heating

44
Q

6.28P
Give a short description of how radiation (include which type) can be used to detect leaks underground

A

-Gamma source added to water
-GM tube follows path of pipe & detects higher levels of radiation where leak is present

45
Q

6.28P 6.34P
Give a short description of how radiation (include which type) can be used to diagnose cancer

A

-Patient injected with radioactive tracer
-Radioactive isotope concentrates in particular organ/cancerous tumour
-Emits positron which interacts with electron in body, releases gamma rays
-Detected by detector

46
Q

6.28P
Give a short description of how radiation (include which type) can be used to check paper thickness

A

-Beta particles
-Detector on opposite side of sheet detects count rate of radiation travelling through paper
-Too thin = high count rate
-Too thick = low count rate
-Computer corrects force on rollers

47
Q

6.28P
Give a short description of how radiation (include which type) can be used for smoke alarms

A

-Alpha particles
-Detector has electrical circuit w/ gap between 2 electrically charged plates
-Alpha particles ionise molecules in air -> current flows across gap (completes circuit)
-Smoke interferes -> current slows (ions have slowed) -> alarm sounds

48
Q

6.29
State the (8) dangers (effects) of ionising radiation

A

-Radiation sickness
-Diarrhoea
-Vomiting
-Weak immune system
-Burns & blisters
-Sepsis
-Cataracts
-Cancer

49
Q

6.30P 6.31
How can we protect ourselves from radiation?

A

-Increase distance from source
-Minimise time spent near source
-Shielding (Putting barrier between source & person for radiation to be absorbed by)
-Wear a dosimeter to monitor exposure
-Limit dose & use source with short half-life

50
Q

6.32
Define the term irradiated
Define the term contaminated

A

-Exposed to nearby radiation
-Particles of radioactive material on skin/inside body

51
Q

6.32
Compare irradiation and contamination (2 things)

A

-Irradiation ends when source is removed, contamination ends when all material has decayed
-Irradiation does not cause object to become radioactive, contamination does

52
Q

6.33P
How can a tumour be treated internally? What is a benefit to this?

A

-Beta emitter inside/very close to tumour to destroy it
-Benefit: Precise to tumour, less damage to healthy tissue

53
Q

6.33P
How can a tumour be treated externally? What is a problem with this?

A

-Beams of radiation directed at tumour from different directions to destroy it
-Con: Healthy tissue may also be damaged

54
Q

6.34P
Why are different tracers used to diagnose problems in different areas of the body?

A

Different parts of the body absorb different tracers

55
Q

6.35P
Explain why isotopes used in PET scanners have to be produced nearby and what they are produced in

A

-Cyclotrons
-Need to have short half-life to MINIMISE RISK OF RADIOACTIVITY to patient
-Will fully decay in short time so need to be used quickly

56
Q

6.36P
Evaluate the advantages and disadvantages of nuclear power

A

ADVANTAGES:
-Low emission of CO₂ (only releases when building power plants)
-Reliable
-Extremely energy efficient
-Saves more lives than it takes

DISADVANTAGES:
-Accidents & disasters
-Nuclear waste difficult to dispose of
-Used to create nuclear bombs -> pollution

57
Q

6.37P
What can nuclear fission, fusion and radioactive decay be used for?

A

Supply energy

58
Q

6.38P
Define the term daughter nuclei

A

Smaller nuclei that atom breaks down into

59
Q

6.38P 6.44P
Describe the process of nuclear fission using uranium-235 as an example

A

-Neutron fired at high speed to hit U-235 nuc
-Nuc -> unstable bc gained neutron
-Nuc splits -> 2 smaller daughter nuclei
-Energy & multiple neutrons released

60
Q

6.39P
Describe what will happen if the neutrons hit too many fuel rods in a reactor

A

Reactor overheats -> core melts

61
Q

6.40P
State 3 features of a nuclear fission reactor

A

-Fuel rods
-Control rods
-Moderator

62
Q

6.40P
Describe the role fuel rods play in a reactor

A

-Neutrons leave fuel rods at high speeds
-Move through moderator
-Absorbed by control rod/another fuel rod -> another reaction

63
Q

6.40P
Describe the function of the control rods in a reactor

A

-Control r. reaction (lowered & pulled up)
-Lowered: absorb more neutrons -> ↓ r. reaction

64
Q

6.40P
Describe the function of the moderator in a reactor

A

Slows neutrons -> ↑ likelihood will be absorbed by fuel rods and -> split nuc

65
Q

6.41P
a) Explain how thermal energy from the chain reaction in a reactor is used to generate electricity in a nuclear power station
b) Which energy transfer is present here?

A

a) -Superheated water from reactor passes through heat exchanger
-At ↑ pressure
-Produces steam
-Turns turbine
-Turns generator
b) KE->electrical

66
Q

6.42P
Use one word to describe the products of nuclear fission

A

Radioactive

67
Q

6.43P
What is the energy source for stars?

A

Nuclear fusion

68
Q

6.43P 6.44P
What is nuclear fusion?

A

Small nuceli combine -> 1 large nuc
Releases E

69
Q

6.45P
Why are high temperatures & pressures necessary for carrying out nuclear fusion?

A

-All nuclei = + (bc protons) -> strong electrostatic F of repulsion
-↑ pressure squeezes nuclei together
-↑ temp = enough E to overcome F of repulsion

70
Q

6.46P
State 3 disadvantages of nuclear fusion

A

-Very ↑ temp & pressure needed -> difficult to sustain
-Expensive
-So far none of experimental reactors produced more E than was used to heat H₂ nuclei

GCSE Physics (10 decks)

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