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 THE 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.