P2.1 - Conduction.

Question 1

Metals conduct energy better than..

Answer 1

non-metals do

Question 2

Copper is a better conductor than..

Answer 2

steel

Question 3

Glass conducts better than..

Answer 3

wood

Question 4

The best insulators are…

Answer 4

• non-metal materials

- eg wood/fibre glass

Question 5

Conduction of energy depends on..

Answer 5

the material

Question 6

The greater the thermal conductivity of a material…

Answer 6

the more energy per second it transfers by conduction

Question 7

The bigger the temperature gradient…

Answer 7

the more thermal energy will be transferred

Question 8

Energy transfer per second through a layer of insulating material depends on:

Answer 8

• temperature difference across the material
• thickness of the material
• thermal conductivity of the material

Question 9

Good insulators have to have …

Answer 9

a low thermal conductivity

Question 10

Why do good insulators have to have a low thermal conductivity?

Answer 10

so energy transfer through them is very low

Question 11

Ways to increase insulation:

Answer 11

• thermal conductivity of material should be as low as possible
• thickness of material should be a thick as possible

Question 12

Why are metals good conductors?

Answer 12

• metal atoms have many free electrons
• these move around/vibrate
• energy is transferred to neighbouring electrons like this

Question 13

Why are metals cold to human touch?

Answer 13

because they are transferring the heat

• from you hand
• at a very fast pace

Question 14

Why are some metals better conductors than others?

Answer 14

• atoms have different sizes/atomic weights

- which changes the pattern of thermal conductivity

Question 15

Low thermal conductivity is caused by? (particles)

Answer 15

as there is less energy transfer between electrons

Question 16

The rate of energy transfer in houses can be reduced by? (5 points)

Answer 16

• loft insulation
• cavity wall insulation
• double glazed windows
• aluminium foil behind radiators
• external walls thicker bricks and lower thermal conductivity

Question 17

Loft insulation description

Answer 17

layer of insulating material over/under loft floor

Question 18

Loft insulation process

Answer 18

• slows convection (warm air rising to the top of the house)

- through ceilings and then from escaping to outside

Question 19

Convection

Answer 19

causes warm air to rise

Question 20

Cavity wall insulation description

Answer 20

insulating layer between inner/outer walls

Question 21

Cavity wall insulation process

Answer 21

-slows convection of heat from rooms to outside

Question 22

Example of trapped heat being a great insulator

Answer 22

• padded jackets

- maintain body heat

Question 23

Double glazing description

Answer 23

-2 panes of glass in window with air/vacuum in space between them

Question 24

Double glazing process

Answer 24

• as air is a great insulator
• slows conduction of heat from rooms to outside through windows
• vacuum prevents convection of heat

Question 25

Foil behind radiators description

Answer 25

-layer of reflective material on walls behind radiators

Question 26

Foil behind radiators process

Answer 26

• reflects radiation back into room

- reduces rate of heat loss by radiation from radiators towards wall

Question 27

Most common ways of heating homes:

Answer 27

• electric/gas heaters
• gas/oil-fired central heating
• solid fuel stores