the particle model - topic 13 Flashcards

1
Q

what is density

A

a substances mass per unit volume

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2
Q

density =

A

mass/volume

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3
Q

how to measure density of a liquid

A
  1. put measuring cylinder on balance and zero the
    balance
  2. add 10ml of liquid and record mass
  3. add 10ml and record mass and volume
  4. repeat and find average then use density = mass/vol
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4
Q

how to measure density of a solid

A
  1. measure object’s mass with balance
  2. fill eureka can with water and let it drain
  3. place empty measuring cylinder under spout
  4. put solid in can and measure vol of water displaced
  5. density = mass/vol
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5
Q

why are solids solid

A

strong forces of attraction hold the particles close together in a fixed, regular lattice and there is not much energy in KE stores so they vibrate about fixed positions

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6
Q

why are liquids like they are

A

they have weaker forces of attraction between particles and some are able to move past each other. They also have more energy in KE stores so they move more randomly

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7
Q

why are gases like they are

A

they have no forces of attraction and have more energy in KE stores and so are free to move in random directions

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8
Q

kinetic theory of matter

A

a theory explaining how particles in matter behave by modelling these as tiny balls

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9
Q

internal energy

A

the total energy that a systems particles have in their KE and potential energy stores

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10
Q

why do particles in a system vibrate and move around

A

they have energy in their KE stores

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11
Q

more energy in KE store =

A

faster movement

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12
Q

further apart particles =

A

more energy in this store

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13
Q

more energy in thermal store =

A

higher temperature

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14
Q

what does temperature measure

A

how much energy is in thermal store

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15
Q

when temp increases …..

A

the particles vibrate and move around faster but the positions of the particles relative to each other don’t change

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16
Q

cooling a system does what to energy

A

reduces energy of the particles

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17
Q

what is the coldest anything can ever get

A

-273 degrees celsius

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18
Q

what is absolute zero

A

as little energy in their KE stores as possible

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19
Q

how to convert temp in C to temp in K

A

temp in C + 273

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20
Q

how to convert temp in K to temp in C

A

temp in K - 273

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21
Q

how to go from solid to liquid

A

melting

22
Q

how to go from liquid to solid

A

freezing

23
Q

how to go from solid to gas

A

sublimating

24
Q

how to go from liquid to gas

A

boiling

25
Q

how to go from gas to liquid

A

condensing

26
Q

what happens to particles and forces when a system is heated and changes state

A

energy is transferred to potential energy store, particles move apart and forces get weaker

27
Q

why is mass conserved during changes of state

A

because the number of particles remains the same, only the properties are changing

28
Q

what is specific heat capacity

A

the amount of energy needed to raise the temperature of 1kg of a substance by 1 degrees celsius

29
Q

change in thermal energy =

A

mass x specific heat capacity x temperature change

30
Q

investigating specific heat capacity

A
  1. place container on balance and fill with water and record mass
  2. connect power supply to immersion heater and ammeter which is also connected to heater and put thermometer in water
  3. measure initial temp and set pd of power supply
  4. start the stop watch
  5. current should not change as temp increases
  6. once temp increases by 10C, stop stopwatch and heater
  7. Use E=i x v x t to work out energy supplied by heater
  8. SHC equation and calculate the specific heat capacity
31
Q

what is specific latent heat

A

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

32
Q

specific latent heat of fusion

A

changing state between solid and liquid

33
Q

specific latent heat of vaporisation

A

changing state between a liquid and a gas

34
Q

thermal energy for change of state =

A

mass x specific latent heat

35
Q

how do we investigate changing matters of state

A
  1. fill beaker with crushed ice + place thermometer in
  2. set up equipment ( beaker with thermometer on bunsen burner)
  3. measure initial temp
  4. start stop watch and turn on bunsen burner
  5. every 20s, record temp and state of ice
  6. continue until ice melts and water boils
  7. turn off stop watch and bunsen burner and plot results
36
Q

as gas particles move at high speeds

A

they collide into each other and the walls of the container they are in and when they collide with a surface they exert a force on it.

37
Q

as temp increases

A

faster movement and therefore more collisions

38
Q

what happens to gas pressure and force as temp increases

A

increase in net force and gas pressure

39
Q

what happens to the pressure if temp is constant and there is increasing volume

A

particles get more spread out and hit walls of container less and lowers gas pressure

40
Q

how are pressure and volume related

A

they are inversely proportional

41
Q

what happens to the volume of gas if internal and external pressure is equal

A

the volume of the gas and container is constant

42
Q

how does doing work affect temp

A

it increases its internal energy which can increase its temp

43
Q

pressure 1 X volume 1

A

pressure 2 X volume 2

44
Q

how does heating a system change the energy within the system

A

heating a system transfers energy to its particles, so heating a system always increases its internal energy of the system which also leads to an increase in temperature or change in state

45
Q

how do you reduce unwanted energy transfer

A

wrap the container in a thermally insulating material and place it on an insulating surface.

46
Q

why does thermal insulation reduce unwanted energy transfer

A

thermal insulators reduce the rate at which energy is transferred by heating, which means less energy is transferred to the thermal energy stores of the surrounding.

47
Q

what is the effect of changing the temperature of a gas

A

the hotter it is, the fasters its particles move. Faster particles and more collisions with the walls of the container in a given time both lead to an increase in net force and gas pressure

48
Q

what is the effect of changing the volume of a gas

A

if the temperature is kept constant, increasing the volume of a gas means the particles get more spread out so the particles hit the walls of the container less often and gas pressure decreases

49
Q

how can gases be compressed or expanded by pressure change

A

if a container can easily change its size, then any change in these pressures will cause the container to compress or expand

50
Q

why is density of a substance highest when a solid

A

the particles are packed close together - there is a lot of mass in a given volume and as density = mass x volume the density is high

51
Q

why are liquids less dense than solids

A

because they have fewer particles in a given volume

52
Q

why are gases less dense than liquids and solids

A

because gases have particles spaced far apart, a substance in gas form is less dense