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gcse PE > Physics - P3 - Particle Model Of Matter & P4 - Atomic Structure > Flashcards

Physics - P3 - Particle Model Of Matter & P4 - Atomic Structure Flashcards

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1
Q

what is density ?

A

density is a measure of the ‘compactness’ of a substance. It relates the mass of a substance to how much space it takes up, e.g its mass per unit volume

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2
Q

how do you calculate density ?

A

density= mass/volume

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3
Q

what does the density of something depend on ?

A
  • what the object is made of
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4
Q

what is the particle arrangement for a dense substance ?

A
  • particles tightly packed together
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5
Q

what is the particle arrangement for a less dense substance ?

A
  • particles are more spread out
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6
Q

what happens when a material is compressed ?

A

particles would move closer together and become more dense

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7
Q

what is the composition of solids like ?

A
  • strong forces of attraction hold particles close together
  • fixed regular arrangement
  • particles don’t have much energy so vibrate at fixed positions
  • density of a substance highest in solid form
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8
Q

what is the composition of liquids like ?

A
  • weaker forces of attraction
  • particles are close together but can move past each other
  • form irregular arrangements
  • have more energy than particles in a solid
  • move in random directions at low speeds
  • less dense than solids
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9
Q

what is the composition of gases like ?

A
  • almost no forces of attraction
  • particles have more energy than liquids and solids
  • free to move
  • travel in random directions and speeds
  • the least dense
  • compressible - reduces distance between the particles
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10
Q

what is internal energy ?

A

the total energy that its particles have in their kinetic and potential energy stores

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11
Q

what does heating the system do ?

A

transfers energy to its particles
they move faster, because they have more energy in their kinetic energy store
increases internal energy

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12
Q

what does the size of the temperature change depend on ?

A

the mass of the substance
what it’s made of
energy input

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13
Q

what happens if the substance is heated enough ?

A

particles will have enough energy in their kinetic energy stores to break the bonds holding them together - change of state

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14
Q

what is solid to liquid ?

A

melting

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15
Q

what is liquid to solid ?

A

freezing

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16
Q

what is liquid to gas ?

A

boiling or evaporating

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17
Q

what is gas to liquid ?

A

condensing

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18
Q

what is solid to gas ?

A

sublimation

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19
Q

what is gas to solid ?

A

deposition

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20
Q

what type of change is a change of state ?

A

a physical change, it’s the same substance in a different form, it’s reversible

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21
Q

what happens to the particle bonds during condensing or freezing ?

A

bonds are forming between particles
this releases energy so
internal energy decreases but the temperature doesn’t go down until all of the substance has condensed or froze

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22
Q

what happens when a substance is melting or boiling ?

A

-internal energy increases
-this is because you’re still putting energy in
-energy is used for breaking intermolecular bonds instead of raising temperature

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23
Q

what is specific latent heat ?

A

the energy needed to change 1kg of a substance from one state to another without changing its temperature

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24
Q

what happens with specific latent heat when cooling ?

A

specific latent heat is the energy released by a change in state

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25
Q

what is the specific latent heat for changing between a solid and a liquid called ?

A

specific latent heat of fusion

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26
Q

what is the specific latent heat for changing between a liquid and a gas called ?

A

specific latent heat of vapourisation

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27
Q

how do you calculate the energy needed for a change in state ?

A

energy for a change of state = specific latent heat x mass

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28
Q

what’s the difference between specific heat capacity and specific latent heat ?

A

specific heat capacity is the temperature rise of 1 degree Celsius, specific latent heat is about changes of state where there’s no temperature change

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29
Q

what happens when you increase the temperature from gas ?

A

you transfer energy into the kinetic energy into the kinetic energy stores of its particle, the higher the temperature, the higher the average energy

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30
Q

what do faster particles and more collisions with the walls of the container lead to ?

A

an increase in net force - gas pressure

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31
Q

if the temperature is constant, what will increasing the volume of gas do ?

A

particles get more spread out, gas pressure decreases

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32
Q

describe the relationship between pressure and volume ?

A

inversely proportional- when volume increases, pressure decreases

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33
Q

describe the relationship between atmospheric pressure and height ?

A

it decreases with height

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34
Q

if you transfer energy by applying a force, then you do work, what does doing work on a gas do ?

A

increase the gases internal energy, which increases its temperature

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35
Q

what is radioactive decay ?

A

where unstable isotopes tend to decay into other elements and give out radiation as they try to become more stable

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36
Q

radioactive decay is random. What does this mean ?

A

if you have lots of unstable nuclei you can’t say weather any one of them is going to decay, and you can’t do anything to make a decay happen. it’s completely unaffected by physical conditions like temperature or any sort of chemical bonding

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37
Q

what do radioactive substances emit ?

A

ionising radiation

38
Q

what is ionising radiation ?

A

radiation that knocks electrons off atoms creating positive ions. The ionising power of a radiation source tells you how easily you can do this

39
Q

what are the 3 different types of ionising radiation we need to know ?

A
  • alpha
  • beta
  • gamma
40
Q

what is alpha radiation ?

A

when an alpha particle is emitted from the nucleus

41
Q

what is an alpha particle ?

A

2 neutrons and 2 protons, the same as helium

42
Q

what happens when an atom decays by emitting an alpha particle ?

A

-2 protons and 2 neutrons are lost from the nucleus
-This is because protons have a charge of +1, alpha emissions decreases the charge on the nucleus
-The mass number decreases by 4

43
Q

describe properties of an alpha particle ?

A
  • big
  • heavy
  • slow moving
  • stopped quickly
  • don’t penetrate into materials very far
  • are absorbed by a sheet of paper
44
Q

what do alpha particles do due to their size ?

A

bash into a lot of atoms and knock of electrons before they slow down so they create a lot of ions

45
Q

what is a beta particle ?

A

a fast moving electron released by a nucleus

46
Q

what happens when a nucleus decays by beta decay ?

A
  • a neutron turns into a proton as the nucleus releases a beta particle
  • This increases the charge on the nucleus by 1 but leaves the mass number unchanged
47
Q

what are the properties of a beta particle ?

A
  • small, they have virtually no mass and a charge of -1
  • fast
  • ionising
  • penetrate quite far into the material before colliding
  • have a range in air of a few metres
  • can be absorbed by a sheet of aluminium
48
Q

what are gamma rays ?

A
  • very short wavelength electromagnetic waves released by the nucleus
  • gamma rays have no mass or charge.
  • They are a way of getting rid of excess energy
49
Q

what do gamma rays do ?

A
  • penetrate far into materials without being stopped
  • weakly ionising because they tend to pass through rather than collide with atoms
  • when they hit something they do damage
  • can be absorbed by thick sheets of lead or metres of concrete
50
Q

you an write alpha and beta nuclear equations which show what atoms you start with, what radiation is emitted and what atoms you’re left with, why don’t you write nuclear equations for gamma decays ?

A

because they do not change atomic mass or the atomic number of an atom

51
Q

what is radiation measure with ?

A

a Geiger Muller tube, which records the count rate

52
Q

what is half life ?

A

the time it takes for the amount of radiation emitted by a source to halve

53
Q

why is half life used ?

A

to make predictions about radioactive sources, even though their decays are random

54
Q

what is half life used to find ?

A

the rate at which a source decays, its activity

55
Q

what is the activity measured in ?

A

becquerels

56
Q

what happens to the activity, every time a radioactive nucleus decays to become a stable nucleus ?

A

the activity as a whole will decrease - older sources emit less radiation

57
Q

what is the definition of half life?

A

the time it takes for the number of nuclei of a radioactive isotope in a sample to halve

58
Q

what does a very short half life mean ?

A

the activity falls quickly, as the nuclei are unstable so rapidly decays

59
Q

what can sources with a short half life be ?

A

dangerous due to high amount of radiation they emit at the start, but they quickly become safe

60
Q

what does a long half life mean ?

A

the activity falls more slowly because most of the nuclei doesn’t decay for a long time - they just sit there releasing small amounts of radiation over a longer period

61
Q

what can sources with a long half life be ?

A

dangerous as nearby areas are exposed to radiation for years

62
Q

how do you calculate half life ?

A

see how many half life’s it takes to get to the final number by dividing by 2 until you have the original number

63
Q

what is irradiation ?

A

where you’re exposed to radiation

64
Q

how can you prevent irradiation ?

A

-by keeping sources in lead lined boxes,
-by standing behind barriers
-being in a different room
- using remote controlled arms to handle sources

65
Q

what is contamination ?

A

when unwanted radioactive atoms get onto or into a material

66
Q

give an example of contamination

A

if you touch a radioactive source without wearing gloves

67
Q

how do you prevent contamination ?

A
  • wear gloves
  • use tongs
  • wear protective suits
68
Q

which types of radiation are the most harmful to the outside of your body and why ? - irradiation

A

beta and gamma
- they can penetrate into the body and get to the delicate organs

69
Q

what type of radiation is the least harmful to the outside of your body and why ? - irradiation

A

alpha
- they can’t penetrate into skin and organs
- easily blocked by small air gap

70
Q

what type of radiation is the most harmful to the inside of your body and why ? - contamination

A

alpha
- they do lots of damage in delocalized areas

71
Q

which types of radiation are the least harmful to the inside of your body and why ? - contamination

A

gamma and beta
- they mostly pass straight out without doing much damage (they have less ionizing power)
-

72
Q

what is radiation dose ?

A

a measure of the risk of harm to your body due to exposure to radiation

73
Q

what does radiation dose depend on ?

A
  • the type of radiation
  • the amount of radiation
74
Q

what are you more at risk of if you have a higher radiation dose ?

A

cancer

75
Q

what is radiation dose dependent on ?

A

sieverts

76
Q

what is background radiation ?

A

a low-level radiation that is present at all times, wherever you go

77
Q

what are the different background radiation stores ?

A
  • radioactivity of natural unstable isotopes
  • radiation from space
  • radiation from man-made sources
78
Q

explain radiation of natural unstable isotopes ?

A

it’s radiation that is happening all around us, found in our
- food
- air
- building materials
- rocks

79
Q

explain radiation in space ?

A

radiation from space is known as cosmic rays, which comes mostly from the sun

80
Q

give examples of radiation made from man made sources

A
  • fallout from nuclear weapons tests
    -nuclear accidents
    -dumped nuclear waste
81
Q

how can radiation you’re exposed to depend on location ?

A
  • ## if you live at higher altitude
82
Q

how can radiation you’re exposed to depend on your occupation ?

A
  • nuclear industry workers are exposed to 10x the normal amount of radiation
  • radiographers work in hospitals using ionizing radiation
  • underground workers because of the rocks around them
83
Q

what does the extent of harmful radiation depend on ?

A
  • the energy and penetration of the radiation
  • the amount of exposure you’ve had to the radiation
84
Q

how is radiation used medically ?

A

medical tracers- help doctors investigate whether the patients internal organs are functioning properly

85
Q

what is radiotherapy ?

A

a treatment of cancer using ionising radiation - gamma rays

86
Q

what are the disadvantages to radiotherapy ?

A
  • it damages normal cells
  • makes the patient feel ill
87
Q

what are the disadvantages of medical tracers ?

A
  • tiny risk of cancer
88
Q

what is nuclear fission ?

A

a type of nuclear reaction that’s used to release energy from large and unstable atoms by splitting them into smaller atoms

89
Q

describe a chain reaction that can occur during nuclear fission

A

2 or 3 neutrons are released, and if any of the neutrons are moving slowly enough to be absorbed by another nucleus, more fission could occur

90
Q

what is the amount of energy released by fission in a nuclear reactor controlled by ?

A

how quickly the chain reaction can occur

91
Q

what is nuclear fusion ?

A

the opposite of nuclear fission, 2 light nuclei collide at high speed and join to create a larger, heavier nucleus

92
Q

give an example of nuclear fusion ?

A

hydrogen nuclei can fuse to produce a helium nucleus

gcse PE (5 decks)

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