9) Transfer of Thermal Energy Flashcards
Define conduction.
Conduction is the process by which thermal energy is transmitted through a medium from one particle to another.
Explain how heat is conducted through a solid rod.
(in terms of the atoms inside solid)
1) When one end of the rod is heated, the atoms there gains energy and vibrate more vigorously.
2) These atoms collide with their less energetic neighbours.
3) Some of their energy is transferred to these neighbouring atoms, which in turn gain kinetic energy.
4) In this way, thermal energy is passed along the rod by the vibrating atoms.
State why conduction of heat is faster in metals compared to non-metals.
Metals contains free electrons which helps to conduct heat faster throughout the solid.
State one application for a good conductor of heat.
1) Used in pans and pots to allow food to be cooked faster.
2) Used in heat sinks to allow heat to be transferred away faster.
State one application for an insulator of heat.
1) Handles of pots and pans to allow them to be touched without burning.
2) Used in roofs and walls of house to keep the house cool in hot weather (keep the house warm in cold weather).
Define convection.
Convection is the process by which thermal energy is transmitted from one place to another by the movement of heated gas or liquid.
Describe how a land breeze is formed.
1) During the night, the land loses heat faster than the sea.
2) The air above the sea heats up faster than the air above the land.
3) The hot less dense air above the sea rises.
4) The cooler denser air above the land moves towards the sea forming a land breeze.
Describe how a sea breeze is formed.
1) During the day, the land heats up faster than the sea.
2) The air above the land heats up faster than the air above the sea.
3) The hot less dense air above the land rises.
4) The cooler denser air above the sea moves towards the land forming a sea breeze.
Describe how convection works to cool down a room using air conditioner.
1) The air near the top of the room is cooled by the air conditioner. They becomes denser and sinks.
2) The warmer, less dense air near the bottom of the room rises to the top.
3) This process repeats to create a convection currrent to cool down the room.
Describe how convection works to heat up a pot of water.
1) When the bottom of the pot is heated, the water near the bottom of the pot becomes heated and expand.
2) They becomes less dense and rises up to the top of the pot.
3) The cooler denser water near the top of the pot sinks.
4) This process repeats to create a convection currrent to heat up the pot of water.
Define radiation.
Radiation is the process by which thermal energy is transferred by electromagnetic waves.
State the type of surface that is a poor absorber of radiation.
A shiny and white surface.
State the type of surface that is a poor emitter of radiation.
A shiny and white surface.
State the type of surface that is a good emitter of radiation.
A dull and black surface.
State the type of surface that is a good absorber of radiation.
A dull and black surface.
Explain why the the radiator fins at the back of the fridge should be painted black.
Black surfaces are good radiators of heat.
Heat can then be transferred quickly away from the fridge keeping the fridge cold.
Explain why the thermal blanket used to cover a person who is cold has a shiny surface.
1) Shiny surfaces are poor radiators of heat.
2) Heat loss through radiation would be slower and thus keep the person warmer for a longer period of time.
