07. P2 Energy Transfer by Heating

Question 1

What state of matter does conduction occur in?

Answer 1

Solid

Question 2

What property describes how rapidly heat moves through a solid?

Answer 2

Thermal Conductivity

Question 3

Explain why birds fluff up their feathers in winter.

Answer 3

Fluffing feathers traps air, air is a good insulator so less energy is as lost through conduction.

Question 4

A metal and a wooden pole have been out all night on a frosty evening, in the morning you pick one up with your left hand and one with your right. Which one feels coldest and why?

Answer 4

Metal feels coldest as it is a good conductor so conducts more energy away from your hand each second. So feels colder, but BOTH are actually at the same temperature.

Question 5

Explain why a mug of cappucino with milk froth on the top, cool down slower than an plain cup of tea.

Answer 5

Frothy milk has air trapped in it. Air is a good insulator so reduces heat loss by conduction.

Question 6

What is the name given to a poor conductor?

Answer 6

Insulator

Question 7

State the name given to thermal energy transfer in the form of a wave?

Answer 7

Infrared radiation

Question 8

How does the temperature of the object affect the amount of IR radiation given out?

Answer 8

Hotter = more radiation given out per second

Question 9

What objects are the best emitters of IR radiation?

Answer 9

Black and Matt objects

Question 10

What objects are the best absorbers of IR radiation?

Answer 10

Black and Matt objects

Question 11

Which objects are the best reflectors of IR radiation?

Answer 11

White and shiny

Question 12

If you pour a freshly boiled cup of tea. Explain why it cools down at a quicker rate just after it has been freshly boiled rather than 5 minutes later.

Answer 12

The temperature difference between the room and the cup of tea is at its greatest immediately after pouring it.

Question 13

PHYSICS ONLY - State the three main types of greenhouse gases?

Answer 13

Methane, Carbon Dioxide, and Water vapour

Question 14

PHYSICS ONLY - State the difference between IR rays given off by the Sun and the Earth?

Answer 14

IR rays from the Sun has a shorter wavelength

Question 15

PHYSICS ONLY - Explain how the presence of greenhouse gases keep the Earth warm.

Answer 15

Some of the IR rays emitted from the Earth are absorbed by the greenhouse gases, and then emitted out in all directions with some of them going back towards the Earth.

Question 16

PHYSICS ONLY - Explain the effect of an increasing amount of greenhouse gases present in the atmosphere on the Earth.

Answer 16

Global warming - leading to issues such as polar ice caps melting, flooding to low lying land, destruction of habitats etc.

Question 17

List the different places heat is lost from a house.

Answer 17

Roof, Walls, floor, windows, Draughts

Question 18

State what can be added to a house to reduce heat loss through the house?

Answer 18

Loft insulation

Question 19

State what can be added to a house to reduce heat loss through the walls?

Answer 19

Cavity wall insulation

Question 20

State two things which can be added to a house to reduce heat loss through windows?

Answer 20

Double glazing and curtains

Question 21

Describe how loft insulation reduces heat loss through the roof.

Answer 21

Loft insulation has air pockets trapped in it. Air is a good insulator so reduces heat loss by conduction

Question 22

Describe how cavity wall insulation reduces heat loss through the roof.

Answer 22

Cavity wall insulation has air pockets trapped in it. Air is a good insulator so reduces heat loss by conduction

Question 23

How does a sheet of aluminium foil between a radiatior panel and wall help reduce energy losses?

Answer 23

Radiation from the radiator is reflected away from the wall and so reduces the rate of energy transfer into the wall by radiation

Question 24

How do double glazed windows help to reduce energy losses?

Answer 24

The air gap between the two panes of glass reduces heat loss by conduction, as air is a good insulator.

Question 25

The energy transfer per second through a layer of insulating material depends on what three factors?

Answer 25

1) Temperature difference, 2) material thickness, 3)thermal conductivity of the material

Question 26

What happens to the temperature of an object that absorbs more IR radiation than it emits?

Answer 26

The temperature increases

Question 27

What is the name given to a type of body that does not reflect or transmit any radiation?

Answer 27

A black body object

Question 28

What is the name given to the best possible emitter of infrared radiation?

Answer 28

A black body object

Question 29

Why do rescue teams use light-coloured shiny blankets when treating someone?

Answer 29

To keep people warm - light, shiny surfaces reflect the heat emitted from the body back to the person, and also emit less radiation than if it was a dark, matt surface

Question 30

What factors determine the rate of thermal energy transfer?

Answer 30

Temperature Difference, Thickness of Material, Thermal Conductivity of material.