Ch 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.
Used in pans and pots to allow food to be cooked faster.
Used in heat sinks to allow heat to be transferred away faster.
State one application for an insulator of heat.
Handles of pots and pans to allow them to be touched without burning.
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 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 air 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 abosorber 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.
