CONVECTION CURRENTS AND THE MANTLE 1 Heat is

CONVECTION CURRENTS AND THE MANTLE

1. Heat is always transferred from a WARMER substance to a COOLER substance.

2. Cold is the absence of HEAT.

3. There are three types of heat transfer:

A. RADIATION –the transfer of energy through EMPTY SPACE.

SUNLIGHT is radiation that warms Earth’s surface.

Radiation takes place with no DIRECT CONTACT between a heat source and an object.

Other familiar forms of radiation include the heat you feel around FLAME or OPEN FIRE.

B. CONDUCTION – heat transfer by DIRECT CONTACT of particles of matter.

When a spoon sits in a hot pot of soup, particles near the bottom of the spoon VIBRATE faster as they are heated, so they bump into other particles and HEAT them.

Heat is transferred from the hot SOUP and the POT to the particles that make up the spoon.

C. CONVECTION – heat transfer by the MOVEMENT of a heated fluid.

Heat particles of fluid begin to FLOW transferring HEAT ENERGY from one part of the fluid to another one.

Convection is caused by differences of TEMPERATURE and DENSITY.

When a liquid is heated, the particles move FASTER and spread APART. This causes density to DECREASE.

When a liquid is cooled, the particles move more SLOWLY and settle together MORE CLOSELY. This causes density to INCREASE.

A constant flow begins as cooler soup CONTINUALLY SINKS to the bottom and warmer soup RISES.

4. WHAT ARE THREE THINGS THAT SET COONVECTION CURRENTS IN MOTION? - Heating and cooling of fluid - Changes in the fluid’s density - The force of gravity

5. HOW LONG DO CONVECTION CURRENTS CONTINUE? As long as heat is added

6. WHAT CAUSES A CONVECTION CURRENT TO STOP? When all of the material has reached the same temperature.

7. Convection currents flow in the Earth’s ASTHENOSPHERE. The heat source for these currents is heat from Earth’s CORE and from the MANTLE.