P2 thermal physics

Question 1

distinguishing properties of solids

Answer 1

• fixed shape
• incompressible
• cannot flow

Question 2

distinguishing properties of liquids

Answer 2

• takes shape from bottom of container
• incompressible
• can flow

Question 3

distinguishing properties of gases

Answer 3

• completely fill volume of container
• can be compressed
• flows very quickly

Question 4

term for change in state from solid to liquid

Answer 4

melting

Question 5

term for change in state from liquid to gas

Answer 5

evaporation

Question 6

term for change in state from gas to liquid

Answer 6

condensation

Question 7

term for change in state from liquid to solid

Answer 7

freezing

Question 8

term for change in state from gas to solid

Answer 8

deposition

Question 9

term for change in state from solid to gas

Answer 9

sublimation

Question 10

structure of of particles in solids

Answer 10

• regular arrangement
• particles v close tg
• vibrate in one place

Question 11

structure of particles in liquids

Answer 11

• irregular arrangement
• particles v close tg (strong intermolecular forces)
• move around randomly and slowly

Question 12

structure of particles in gas

Answer 12

• irregular arrangement
• particles far apart
• move around randomly and quickly

Question 13

why are solids difficult to compress

Answer 13

particles already packed v close tg

Question 14

why cant solids flow

Answer 14

particles held in a fixed, regular arrangement by strong intermolecular forces

Question 15

why cant liquids be compressed

Answer 15

particles are alr v close tg

Question 16

why can liquids flow

Answer 16

• intermolecular forces between particles weaker
• can move past each other, positions not fixed

Question 17

why are gases not dense

Answer 17

• intermolecular forces are extremely weak
• do not attract each other

Question 18

relationship between temperature and motion of particles

Answer 18

as temp increases, KE of particles increases and motion increases

Question 19

what does the random motion of particles in a suspension prove

Answer 19

the kinetic particle model of matter // brownian motion

Question 20

describe and explain brownian motion

Answer 20

• caused by random collisions
• between particles in suspension
• and much smaller, fast-moving particles of fluid

Question 21

describe pressure of a gas

Answer 21

• impact of rapidly moving gas particles with wall of container
• exerts a force

Question 22

how does increasing temp change gas pressure (in terms of particles)

Answer 22

• particles gain more KE
• travel faster in random directions
• hit walls of container more often and with greater force
• increase pressure

Question 23

how does decreasing volume affect gas pressure (in terms of particles)

Answer 23

• decrease distance gas particles have to travel between collisions with walls
• number of collisions between gas particles and walls of container increases
• therefore increase in pressure

Question 24

describe thermal expansion in terms of particles

Answer 24

• increase temp = increase KE, increase mvmt
• in solid, move further apart, v increase
• in fluids, particles move faster and more freely, v increase

Question 25

melting and boiling point of water

Answer 25

0, 100

Question 26

describe condensation in terms of particles

Answer 26

- temp decrease, gas cools - reach boiling point, temp decrease stop - forces between particles become stronger, become closer tg

Question 27

describe solidification (freezing) in terms of particles

Answer 27

- temp decrease, liquid cools - reach freezing point, temp decrease stop - forces between particles become much stronger, can no longer move about, fixed positions

Question 28

describe evaporation in terms of particles

Answer 28

more energetic particles escape from surface of liquid

Question 29

how does evaporation affect temperature of liquid

Answer 29

- fastest particles with most KE escape first - mean speed/energy of remaining particles decrease - temperature of remaining liquid decreases

Question 30

factors affecting evaporation

Answer 30

- temperature - surface area - air movement over a surface

Question 31

how does temperature affect evaporation

Answer 31

- only particles with enough speed/energy can evaporate - increase temp = increase mean speed/energy of particles in liquid - more particles moving fast enough / enough energy to escape - rate increase

Question 32

how does surface are affect evaporation

Answer 32

- only particles near surface of liquid can evaporate - increase number of particles near surface - increase rate

Question 33

how does air movement over a surface affect evaporation

Answer 33

- when evaporate, escaped particles form saturated vapour above surface of liquid - slows rate at which escape - increase air flow = remove evaporated particles, easier for more particles to escape - increase rate

Question 34

differences between boiling and evaporation

Answer 34

- boiling occurs at fixed temperature, evaporation may occur at any temp between melting and boiling point - boiling happens throughout liquid, evaporation only at surface

Question 35

typical good thermal conductors

Answer 35

metals

Question 36

typical bad thermal conductors

Answer 36

non-metals - plastics - glass

Question 37

what are bad thermal conductors known as

Answer 37

thermal insulators

Question 38

describe thermal conduction in solid non-metals in terms of particles

Answer 38

- vibration of particles in fixed lattice - increase in temperature in one part, vibration passed on to neighbouring particles - gradually causes increased vibration/temperature across all material

Question 39

describe thermal conduction in metals in terms of particles, excluding lattice vibration

Answer 39

- delocalised electrons (in metals) not fixed in place - able to move quickly, colliding with atoms and causing increased vibration, raising temp

Question 40

what states of matter does convection occur in

Answer 40

liquids and gases

Question 41

describe convection in terms of particles and density

Answer 41

- when part of fluid heated, expand, particles move further apart - region less dense than surroundings, rise upwards - reach surface, gradually cool, density increase - sink back down, especially if another part of fluid still being heated and rising upwards process repeats

Question 42

does thermal radiation require a medium

Answer 42

no

Question 43

how does thermal radiation travel

Answer 43

infrared radiation

Question 44

how does radiation affect temperature of the earth

Answer 44

- emit > absorb: cool - absorb > emit: warm - emit = absorb: constant temp

Question 45

how does surface colour affect emission of radiation and how does it affect cooling

Answer 45

- black surface better emitter - white surface worse therefore black objects cool more quickly

Question 46

how does surface colour affect absorption and reflection of thermal radiation

Answer 46

- black surfaces good absorbers, poor reflectors - white surfaces poor absorbers, good reflectors

Question 47

how does texture affect emission of thermal radiation

Answer 47

- dull: better emitters - shiny: worse emitters

Question 48

how does texture affect absorption and reflection of thermal radiation

Answer 48

- shiny (very smooth), increase reflectiveness, not good at absorption - dull, decrease reflection, increase absorption

Question 49

describe an experiment to distinguish good/bad emitters of thermal radiation

Answer 49

1. place Leslie's cube on heat-resistant surface, fill with freshly boiled water 2. point IR thermometer at each surface in turn to measure temp

Question 50

describe an experiment to distinguish good/bad absorbers of thermal radiation

Answer 50

1. attach drawing pins to two diff coloured metal surfaces using petroleum jelly 2. place surfaces equal distance from IR lamp or radiant heater 3. turn on heater 4. observe which surface warms up most quickly by noting which pin falls first