Ch 17.2 Heating and the Atmosphere

Objectives:

How are heat and temperature related?

• Heat is the energy transferred from one object to another beacuse of a difference in their temperatures.
• Temperature is a measure of the average kinetic energy of individual molecules or atoms in a substance.

What are the three major mechanisms of heat transfer?

Conduction The transfer of heat through matter by molecular activity. The energy of the molecules is transferred by collisions from one molecule to another.

Convection is the transfer of heat by mass movement or circulation within a substance.  It occurs in fluids like the air and in the oceans.  It can also occur in solids like the Earth’s interior over time.

Radiation travels out in all directions from the source and can travel through the vacuum of space as it requires no medium.  Solar radiation reaches Earth by radiation.

There are four  laws governing radiation

1. All objects, at any temperature, emit radiant energy
2. Hotter objects emit more total energy per unit area than colder objects
3. The hottest radiating bodies produce the  shortest lengths of maximum radiation
4. Objects that are good absorbers of radiation are good emitters as well.

How is the atmosphere affected by each of the three heat transfer methods?

When radiation strikes an object, there are usually three different results:

1. Some energy is absorbed and converted into heat raising the temperature of the object
2. Transparent substances such as air and water vapor transmit the energy resulting in no energy change
3. Some energy may reflect (bounce off) the object without being absorbed or transmitted.

Know picture page 486

Reflection verses scattering

In reflection, the electromagnetic radiation “bounces” off an object with the same intensity that it strikes the object.

In scattering, many weaker waves are dispersed  in different directions.  Scattering explains why a room is sunlight even if it does not have direct access to a window.

See figure 13  page 486

Vocabulary:

• heat
• temperature
• conduction
• convection
• radiation
• reflection
• scattering
• greenhouse effect