P2 - Energy Transfer by Heating

Question 1

define thermal energy

Answer 1

thermal energy is the name for the KE stored by a particle. how much a particle vibrates

Question 2

define temperature

Answer 2

the measure of how hot or cold a body is

Question 3

list the 3 types of heat transfer

Answer 3

• conduction
• convection
• radiation

Question 4

define conduction

Answer 4

the process of thermal energy transfer where vibrations are passed through tightly packed particles

Question 5

list 3 properties of electromagnetic waves

Answer 5

• can travel through a vacuum
• travel at the speed of light
• are reflected or absorbed

Question 6

define a black body

Answer 6

a theoretical body that absorbs and emits all wavelengths of electromagnetic radiation

Question 7

define black body radiation

Answer 7

the radiation emitted by a black body

Question 8

describe the greenhouse effect (6 marks)

Answer 8

1. most radiation travels through Earth’s atmosphere while some are reflected into space
2. Earth absorbs the radiation that reaches the surface
3. Earth emits IR back into atmosphere
4. Some IR escapes atmosphere
5. Some IR is absorbed by gases in atmosphere
6. gases re-emit IR back to Earth which causes the lower atmosphere to warm up

Question 9

define specific heat capacity

Answer 9

the amount of energy that is required to heat 1kg of a substance by 1°C

Question 10

formula for thermal energy using specific heat capacity

Answer 10

energy = mass x SHC x temperature
E = mcΔT
J = kg x J/kg°C x °C

Question 11

list 4 good thermal insulators

Answer 11

• wool
• ceramics
• plastics
• air

Question 12

link poor insulation to global warming

Answer 12

Poorly insulated houses lose more thermal energy. This means it costs more and it requires more energy to continue to heat the house. Fossil fuels are usually burnt to create energy which causes more greenhouse gasses to be released which links to pollution and global warming.

Question 13

explain how vacuums are good for insulating

Answer 13

vacuums stop conduction and convection because they require particles to occur and since there is no air in a vacuum the particles can’t get the thermal energy needed for those processes

Question 14

list 5 common ways that houses are insulated

Answer 14

• double-glazed windows
• loft insulation
• cavity wall insulation
• radiator reflectors
• draught excluders and curtains

Question 15

define payback time

Answer 15

the time it takes (in years) for the cost of insulation to be equalled by savings made from reduced energy costs
(Time to break even)

Question 16

formula for payback time

Answer 16

payback time (years) = cost of insulation / savings yearly

Question 17

explain how a thermos works

Answer 17

1. vacuum- to stop conduction and convection
2. insulator in lid - reduce thermal energy lost through conduction, convection and radiation
3. shiny walls - reflect radiation back into bottle

Question 18

order these from longer to shorter wavelengths:
- blue
- infrared
- ultraviolet

Answer 18

1. infrared
2. blue
3. ultraviolet

Question 19

list the steps for finding the specific heat capacity for copper

Answer 19

1. record the mass of the copper block using a scale
2. Insert the thermometer and immersion heater into holes in the copper block
3. Leave for a few minutes to allow the thermometer to reach equilibrium then record the starting temperature of the thermometer
4. Connect the ammeter and immersion heater to the power pack. Then connect the voltmeter
5. turn on the power pack and record the values on the ammeter and the voltmeter
6. Measure the temperature of the block each minute for 10 minutes

Question 20

List 3 errors in finding the specific heat capacity experiment

Answer 20

• gaps of air between copper and immersion heater
• analogue thermometer so measurements might be read wrong
• takes time to heat the immersion heater at the start