5.3 heat transfer Flashcards
(15 cards)
What is conduction?
Conduction requires a medium such as a solid, liquid, or gas to transfer heat.
When does conduction take place?
It takes place between two objects that are in contact.
What are good conductors of heat?
Metals, such as copper, aluminium, and iron.
What are insulators ( poor conductors ) of heat?
Non-metals, such as plastic, wood, and glass.
How does heat conduct in liquids and gases?
they are poor conductors of heat.
How do you use good conducters of heat?
A cooking pan is made of iron so that the heat transfers quickly to the food -> reduces cooking time.
How do you use poor conductors of heat?
A down / fur jacket keeps us warm by trapping air inside them.
What is convection?
Convection is the transfer of heat from one place to another by the movement of a liquid ( or a gas ). This kind of heat transfer cannot take place in solids.
How does convection occur in liquids and gases?
e.g. When the water on the bottom left corner of a convection tube is heated, the hot water rises. At the same time, the cold water in the tube sinks to take the place of the risen water -> forms a convection current of water.
Explain sea breezes.
During the day, land absorbs energy from the Sun faster than sea water and the land becomes hotter than the sea. Hot air rises from land and cold air blows in from the sea to replace the hot air that has risen -> sea breezes.
Explain land breezes.
At night, the land cools down faster than the sea and the land becomes colder. Hot air rises from the sea and cool air blows from land to sea -> land breezes.
What is radiation?
The transfer of heat from the Sun to the Earth. ( vacuum )
What are good absorbers of radiation?
Dull black surfaces.
What are poor absorbers of radiation?
Shiny silver surfaces.
How do you apply radiation in daily life?
e.g. The heat radiator behind a fridge is usually painted black so that it loses heat easily by radiation.
