P2- Energy Transfer By Heating

Question 1

What are the best conductors of energy?

What are the best insulators? Give some examples.

Answer 1

1) Metals are the best conductors of energy.

2) Non metals such as wool and fibreglass are the best insulators.

Question 2

What can you expect with higher thermal conductivity?

Answer 2

1) The higher the thermal conductivity of a material, the higher the rate of energy transfer through it.

Question 3

What can you expect with the thicker a layer of insulating of a material?

Answer 3

1) The thicker a layer of insulating material, the lower the rate of energy transfer through it.

Question 4

What does the energy transfer per second through a layer of insulating material?

Answer 4

1) The temperature difference across the material.
2) The thickness of the material.
3) The thermal conductivity of the material.

Question 5

How can you reduce the energy transfer as much as possible in an given situation?

Answer 5

1) The thermal conductivity of the insulating material should be as low as possible.
2) The thickness of the insulating layer should be as thick as is practically possible.

Question 6

When would an object emit more infrared radiation?

Answer 6

1) The hotter an object is, the more infrared radiation it emits in a given time.

Question 7

When would humans absorb infrared radiation?

Answer 7

1) Humans absorb infrared radiation when they are in sunlight.

Question 8

What is blackbody radiation?

Answer 8

1) Blackbody radiation is emitted by a body that absorbs all the radiation incident on it.

Question 9

What happens to the intensity of radiation an object releases in regards to temperature?

Answer 9

1) If the temperature of an object is increased, the intensity of radiation it emits is greater at every wavelength.

Question 10

Why would the temperature of an object increase?

Answer 10

1) The temperature of an object increases if it absorbs more radiation than it emits.

Question 11

What factors do the Earth’s temperature depend on?

Answer 11

1) The absorption of infrared radiation from the Sun.

2) The emission of radiation from the Earth’s surface and atmosphere.

Question 12

What is the Specific Heat Capacity of a substance?

How do you work out Specific Heat Capacity

Answer 12

1) The specific heat capacity of a substance is the amount of energy needed to change the temperature of 1kg of the substance by 1 degrees celsius.
2) Use a joule meter to work out the energy transferred and temperature for a measured mass. Then use the equation :
Specific Heat Capacity = Energy transferred / mass x temperature change.

Question 13

Which equation should you use to calculate the energy needed to change the temperature of mass?`

Answer 13

1) Energy = mass x specific heat capacity x temperature change.

Question 14

Give examples of things that are used to heat homes.

Answer 14

1) Electric/gas heaters

2) Gas/oil fired central heating or solid fuel stoves are used to heat homes.

Question 15

How can the rate of energy transfer from houses be reduced?

Answer 15

1) Loft Insulation
2) Cavity wall insulation
3) Double glazed windows
4) Aluminium foil behind radiators
5) External walls with thicker bricks and lower thermal conductivity.

Question 16

What is Cavity Wall insulation?

Why is cavity wall insulation is better than air in the cavity between the walls of a house?

Answer 16

1) Cavity wall insulation is insulation material that is used to fill the cavity between the two brick layers of an external house wall.
2) Cavity wall insulation is better than the air it replaces. It traps the air in small pockets, reducing the rate of energy transfer by conduction.

Question 17

What do solar panels do?

Answer 17

1) Solar panels absorb infrared radiation from the sun and are used to generate electricity directly or top heat water directly.