07. P2 Energy Transfer by Heating Flashcards
What property describes how rapidly heat moves through a solid?
Thermal Conductivity
Explain why birds fluff up their feathers in winter.
Fluffing feathers traps air, air is a good insulator so less energy is as lost through conduction.
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?
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.
What is the name given to a poor conductor?
Insulator
State the name given to thermal energy transfer in the form of a wave?
Infrared radiation
How does the temperature of the object affect the amount of IR radiation given out?
Hotter = more radiation given out per second
What objects are the best emitters of IR radiation?
Black and Matt objects
What objects are the best absorbers of IR radiation?
Black and Matt objects
Which objects are the best reflectors of IR radiation?
White and shiny
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.
The temperature difference between the room and the cup of tea is at its greatest immediately after pouring it.
List the different places heat is lost from a house.
Roof, Walls, floor, windows, Draughts
State what can be added to a house to reduce heat loss through the house?
Loft insulation
State what can be added to a house to reduce heat loss through the walls?
Cavity wall insulation
State two things which can be added to a house to reduce heat loss through windows?
Double glazing and curtains
Describe how loft insulation reduces heat loss through the roof.
Loft insulation has air pockets trapped in it. Air is a good insulator so reduces heat loss by conduction
Describe how cavity wall insulation reduces heat loss through the roof.
Cavity wall insulation has air pockets trapped in it. Air is a good insulator so reduces heat loss by conduction
How does a sheet of aluminium foil between a radiatior panel and wall help reduce energy losses?
Radiation from the radiator is reflected away from the wall and so reduces the rate of energy transfer into the wall by radiation
How do double glazed windows help to reduce energy losses?
The air gap between the two panes of glass reduces heat loss by conduction, as air is a good insulator.
The energy transfer per second through a layer of insulating material depends on what three factors?
1) Temperature difference, 2) material thickness, 3)thermal conductivity of the material
Why do rescue teams use light-coloured shiny blankets when treating someone?
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
What factors determine the rate of thermal energy transfer?
Temperature Difference, Thickness of Material, Thermal Conductivity of material.
