Heat

Question 1

Heat definition

Answer 1

a form of energy which causes temperature to rise when added or fall when drawn out

Question 2

heat capacity

Answer 2

• the heat energy required to change the temperature of a substance by 1 kelvin
• symbol - c
• unit - J/K
• equation - Q = cΔθ

Question 3

specific heat capacity

Answer 3

• the heat energy required to change 1 kg of a substance by 1 Kelvin
• symbol - mc
• units - J/kg/K
• equation - Q = mcΔθ
  (higher means more energy required to change)

Question 4

specific heat capacities of substances

Answer 4

copper - 385
aluminium - 900
ice - 2100
water - 4190

Question 5

latent heat

Answer 5

• the heat required to change a substances state without a change in temperature
• symbol - “L”
• unit - J

Question 6

specific latent heat

Answer 6

• the heat required to change the state of 1 kg of a substance without a change in temperature

Question 7

Latent heat of fusion of ice

Answer 7

330,000

Question 8

Latent heat of vaporisation of water

Answer 8

2300000

Question 9

Inside of a fridge

Answer 9

• heat pump
• volatile liquid = low specific heat capacity
  (B.F.C)
• 1) valve - high pressure liquid to low
  pressure gas (Lv)
  - absorbed heat; cold
• 2) compressor - low pressure gas to high
  pressure liquid (Lv)
  - releases heat energy; hot

Question 10

Latent heat in the body

Answer 10

• hot
• plasma sent to surface capillaries
• sweat
• sweat evaporates (Lv)
• body loses heat energy and cools down

Question 11

conduction

Answer 11

the transfer of heat energy in a solid by passing on kinetic energy from molecule to molecule
(frying pan)

Question 12

Conduction experiment

Answer 12

• water bath
• temperature probe
• wax and thumbtacks
• first to fall = best conductor

Question 13

Convection

Answer 13

the transfer of heat energy by the circulation of heated parts of a fluid
(kettle)

Question 14

Convection experiment

Answer 14

• heat water in a beaker with potassium permanganate

- pp moves with convection currents

Question 15

Radiation

Answer 15

the transfer of heat energy as an electromagnetic wave without the need for a medium
(sun)

Question 16

Radiation experiment

Answer 16

• black can, white can
• thermometer
• boiling water
• black loses heat faster - better radiator

Question 17

solar constant

Answer 17

the amount of heat energy striking 1 m² of the earth’s atmosphere every second
(average = 1.37 Kw/m²)

Question 18

Solar Panels

Answer 18

• dark pipes heat in the sun

- heat moves from warm pipes into cold water

Question 19

insulation in a house

Answer 19

• foam between walls (conduction)
  
  • block draughts (convection)
  • silver foil in walls

Question 20

insulation in a flask

Answer 20

• plastic between layers (conduction)
• lid (convection)
• silver on inside (radiation)

Question 21

u value

Answer 21

the amount of heat energy that is transmitted across 1m² of the surface of a material - so long as there is a temperature difference of 1 kelvin on each side of the material

Question 22

high u value

Answer 22

• good conductor

- old chapel

Question 23

low u value

Answer 23

• bad conductor

- modern house