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physics > P1 MATTER > Flashcards

P1 MATTER Flashcards

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1
Q

what’s the formula for density?

A

d=m/v

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2
Q

describe the thomson model of the atom

A

plum pudding model, sphere of positive charge with negative electrons embedded

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3
Q

what was thomson investigating?

A

cathode rays

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4
Q

what did thomson realise cathode rays were?

A

beams of electrons

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5
Q

what was the rutherford model of the atom?

A

nuclear model, almost all mass is in a tiny, positively charged nucleus, surrounded by a cloud of electrons, atom is mostly empty space

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6
Q

who was rutherford working with?

A

geiger and marsden

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7
Q

what was rutherford’s investigation?

A

fired alpha particles (+) at a piece of thin gold foil, most went through, some deflected and some deflected back to the scientists

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8
Q

how did rutherford’s experiment tell him that the nucleus was positive + small?

A

when alpha particles hit the nucleus, they bounce back (like charges repel, since alpha particles are positive). small bc most particles went straight through, only some deflected

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9
Q

what was the issue w rutherford’s model?

A

the electrons would be attracted to the positive nucleus

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10
Q

what was the bohr model?

A

each nucleus has electrons orbiting it in fixed energy levels/shells

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11
Q

what’s the radius of the nucleus?

A

10^-15m

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12
Q

whats the diameter of an atom?

A

10^-10m

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13
Q

whats the length of a molecule?

A

10^-8m

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14
Q

what’s the relative mass of proton, neutron and electrons?

A

1,1,0.0005

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15
Q

what’s an atom?

A

positively charged nucleus surrounded by negatively charged electrons

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16
Q

define density

A

density is amount of mass in a certain volume

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17
Q

what does density vary vs not vary w?

A

varies w type of material. doesn’t vary w size/shape

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18
Q

what property of an object determines whether it floats or sinks?

A

average density

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19
Q

what does the density have to be of an object that floats?

A

object floats if it has lower average density than fluid

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20
Q

how can you measure density of a liquid?

A

use a eureka can: overfill and let extra water drain away. place a measuring cylinder under the spout then gently lower the object un the can. displaced water = volume of water (according to Archimedes) - measure this using cylinder. then weigh to find mass. do mass//vol

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21
Q

the particles in dif states of matter are the same, so what of the particles is different?

A

arrangement and energy of particles

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22
Q

why are solids only able to vibrate about their fixed positions?

A

they don’t have much energy in their KE stores

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23
Q

why can liquids and gas particles move around more?

A

more energy in KE stores than particles in a solid

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24
Q

what are the arrangements in solids, liquids and gases like and why is this?

A

solids - fixed, regular arrangement w close particles- strong forces of attraction
liquids - particles close but can move past each other, irregular arrangements - weak forces of attraction between particles
gases - particles travel in random directions at high speeds - almost no forces of attraction between particles

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25
Q

where is energy in the thermal store actually held?

A

by particles in their kinetic energy stores

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26
Q

what’s the law of conservation of mass?

A

mass doesn’t change due to a reaction in a closed system - particles just rearrange

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27
Q

how are physical changes different to chemical changes?

A

the material recovers its original properties if the change is reversed in physical changes

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28
Q

what can heating a system do?

A

change energy stored in a system, raise temp, produce change of state

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29
Q

how does boiling happen?

A

when heating liquid, extra energy passes into particles’ KE stores, making them move faster. when enough particles have enough energy to overcome their attraction to each other, bubbles of gas form

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30
Q

how does melting happen?

A

extra energy makes solid particles vibrate faster until the forces between them are partly overcome and particles start to move around

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31
Q

what changes and doesn’t change when a substance changes state?

A

density and volume change but mass does not

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32
Q

whats specific heat capacity?

A

amount of energy needed to raise the temp of 1kg of a substance by 1 degree celcius

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33
Q

what does temperature measure and what is this?

A

measures average internal energy of a substance. internal energy=KE store of particles=thermal energy store of substance

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34
Q

how do you measure specific heat capacity of a substance?

A
  1. use mass balance to measure mass of substance
  2. set up an insulating container containing the liquid, with a thermometer inside and an electric heater connected. connect this to a joulemeter which is connected to a power supply (FOR LIQUID)
    set up an insulating container eg polystyrene cup packed w cotton wool with a metal cylinder inside, a thermometer, electric heater, joulemeter and power supply connected (FOR SOLID)
  3. measure temp of substance and turn on power. when temp increases by 10 degrees, record energy on joulemeter and increase in temp.
  4. rearrange equation to find SHC and repeat experiment 3 times + calculate mean
35
Q

how can u improve the specific heat capacity experiment?

A

add conducting gel between heater and metal cylinder to improve conduction and make results more accurate.
repeat experiment 3x and find mean.
use insulating container to reduce amount of energy that escapes from sides and bottom of the substance you’re investigating. can add lid to further reduce energy losses

36
Q

what’s specific latent heat?

A

amount of energy transferred when 1kg of a substance’s state changes

37
Q

what’s specific latent heat of fusion?

A

amount of energy transferred when 1 kg of a substance melts

38
Q

what’s specific latent heat of vaporisation?

A

amount of energy transferred when 1 kg of a substance evaporates

39
Q

what is needed to break bonds between particles?

A

energy

40
Q

what’s the processes happening in the heating and cooling graphs?

A
41
Q

what happens when a substance condenses/freezes?

A

bonds form between particles which releases energy

42
Q

why doesn’t temp change during melting/boiling/condensing/freezing?

A

energy is being put into forming bonds (conden/fre) and breaking bonds (mel/boi)

43
Q

what does particle theory state?

A

matter is made of v small, constantly moving particles. the warmer it is, the more particles are moving

44
Q

what happens when gas particles collide with something?

A

they exert a force on it, and all these collisions cause a net force on the inside surface of the container. force per unit area = pressure

45
Q

why does no. of particles affect pressure?

A

more particles in a given volume means more collisions with the walls of the container + each other, so the higher the pressure

46
Q

why does changing the temperature change the pressure?

A

energy transferred to the kinetic energy stores of the gas particles and they move faster. tmt the particles hit container walls harder + more often, creating more pressure (rate of successful collisions increases)

47
Q

why is pV = constant?

A

if you put the same amount of mass in a bigger container, pressure decreases and there’s fewer collisions but if you decrease volume, rate of collisions increases so pressure increases

48
Q

what is gas pressure caused by?

A

collisions producing an outward force over a certain area

49
Q

what’s the relationship between temp and pressure of a gas?

A

higher temp = higher pressure

50
Q

why does pressure increase w temp?

A

gas particles have a higher average speed, collide more frequently, so greater force, and pressure

51
Q

what can pressure changes do to gases?

A

can compress/expand them

52
Q

what kind of force does pressure produce on a surface?

A

net force at right angles

53
Q

why does increasing volume of a gas decrease its pressure when at a constant temp?

A

less collisions happen because the particles have more space to move, meaning less force is exerted on the walls of the container

54
Q

describe a simple model of the earth’s atmosphere and atmospheric pressure

A

atmosphere is a layer of gas covering earth. we assume its density is the same everywhere in the simplest model. these gases exert an atmospheric pressure.

55
Q

why does atmospheric pressure vary with height?

A

the lower you are, the greater the column of air above you: theres more air molecules above your head.

56
Q

which factors influence floating and sinking?

A

density of the object and the fluid, upthrust

57
Q

why does pressure in a liquid vary with depth?

A

pressure increases with depth because there’s a greater column of liquid and more water molecules above you the further you go down

58
Q

why is there upthrust on an object when it increases in depth?

A

the bottom of the object experiences a greater force due to pressure increasing w depth, whereas the top experiences less force. this causes a resultant upwards force (upthrust).so pressure differences.

59
Q

why does pressure vary with density?

A

a greater density means a greater pressure because there are more particles above you compared to a less dense fluid

60
Q

how does density cause upthrust to vary?

A

greater density means greater pressure, meaning there’s a pressure difference between the top and bottom of the object, causing upthrust

61
Q

what’s the value of g near earth’s surface?

A

10 N/kg

62
Q

what do the collisions happening in random directions add together to produce?

A

net force at right angles to wall of container

63
Q

what happens to force when pressure increases/decreases?

A

force increases when pressure increases, force decreases when pressure decreases

64
Q

why is the outside of a gas container also under pressure?

A

atmospheric pressure from air

65
Q

what does it mean for pressure if a balloon isn’t expanding or contracting?

A

pressure of gas inside balloon pushing outwards =pressure of air outside balloon pushing inwards

66
Q

what happens to a balloon’s pressure when you increase the gas inside the balloon?

A

force pushing outwards > force pushing inwards, so there’s a net outwards force on walls of balloon, causing it to expand.
as balloon expands, gas particles inside hit walls less often, causing pressure inside balloon to decrease. once pressure inside balloon=atmospheric pressure again, balloon stops expanding

67
Q

what happens to pressure when you reduce pressure inside a balloon?

A

pressure on outside > pressure on inside, so there’ll be a net inward force and the balloon shrinks. this causes pressure inside to increase, as particles hit the walls of the container more often until pressure inside = pressure outside again

68
Q

what happens if you compress a syringe filled w air by pushing hard on the plunger?

A

volume of gas in syringe decreases until pressure is equal to pressure you’re exerting on the plunger

69
Q

how does doing work on a gas increase temperature?

A

it increases its internal energy

70
Q

how can you do work on a gas mechanically eg w bike pump?

A

gas exerts pressure on plunger of pump, and so exerts a force on it. work has to be done against this force to push down the plunger, this transfers energy to the kinetic energy stores of gas particles, increasing internal energy and temp.

71
Q

what happens if work done is done to a pump which is connected to a tyre?

A

some energy will be transferred from the gas to the thermal energy store of the tyre, and the tyre gets warmer as you pump it up

72
Q

what happens when you heat a gas?

A

work is done to it

73
Q

why is there atmospheric pressure?

A

weight of air in atmosphere pushes down on air around us

74
Q

how does atmospheric pressure vary with height?

A

the lower you are the higher the Pa but the higher you are the lower the Pa

75
Q

what’s the graph for atmospheric pressure and height

A

curve. insert image from pg 19

76
Q

why is the graph for atmospheric pressure curved?

A

atmospheric pressure is affected by the density of the atmosphere, which also varies with height

77
Q

how does density vary w height?

A

density of atmosphere gets higher the closer you are to sea level (bc weight of air pushes down on air below it, compressing it)

78
Q

what factor affects density?

A

temp

79
Q

how and why does liquid pressure vary with depth?

A

increases with depth due to the ‘weight’ of the column of liquid directly above the object

80
Q

why is density of a liquid the same everywhere?

A

liquids can’t be compressed (unlike gases’

81
Q

what equation can you use to find difference in pressure?

A

difference in pressure = difference in depth x density x g

82
Q

when will an object float and sink in terms of upthrust?

A

upthrust = weight of fluid displaced means object floats
upthrust < object’s weight: sinks

83
Q

what is upthrust acting on an object equal to?

A

weight of fluid it has displaced

84
Q

how can you make an object float?

A

make the object less dense than the liquid you’re trying to float it on, so it will have displaced a vol of water with a weight equal to its own weight before it’s completely submerged

physics (8 decks)

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