Heat Transfer • The movement of heat from a warmer object to a cooler object is called heat transfer. • There are 3 types of heat transfer: • Radiation • Conduction • Convection
Radiation • The transfer of heat through empty space is called radiation. • There is no direct contact with the heat source and what is being heated. • The Sun warming the Earth is an example of radiation.
Conduction • The direct transfer of heat in solid materials is called conduction. • In conduction, the heated particles of a substance transfer heat to other particles through direct contact. • An example of conduction is when a spoon heats up in a hot pot of soup.
Convection • The transfer of heat by the movement of a heated fluid is called convection. • Fluids include liquids and gases. • During convection, heated particles of a fluid begin to flow, transferring heat energy from one part of the fluid to another.
When a liquid or a gas is heated the particles move faster. • Heat transfer by convection is caused by differences in temperature and density within a fluid. • As they move faster, they spread apart. • Since they are farther apart, they occupy more space and are now less dense. • As the fluid cools, the particles move closer together and density increases. Please click on the graphic for a video demonstration.
Convection Currents • The heating and cooling of a fluid, changes in the fluid’s density and gravity combine to set convection currents in motion. • This flow that transfers heat within a fluid is called a convection current. • Convections currents continue as long as heat is added to a fluid.
Convection in Earth’s Mantle • When the material in the asthenosphere is heated, it becomes less dense and rises. While the cooler material is more dense tends to sink. • Circulating currents carry the warmer material up and the cooler material down. • These circular currents in the asthenosphere are called convection currents. • The circulating convection currents cause the plates of the lithosphere to move.