1. Transfer of Energy

2. The Sun
The heat that eventually causes the earth to warm actually comes from the sun.
The sun is a huge ball of gases, mainly hydrogen. The hydrogen is converted into helium through millions and millions of chemical reactions. The by-product of these reactions is heat.

3. Reaching the Earth
The heat released from the sun’s chemical reactions does not stay near the sun, but radiates away and into space.
So much energy is released through the reactions that some can still reach the earth, even though the earth is far away from the sun.

4. The energy reaches the earth in the form of light.
It can be in the form of radio waves, microwaves, visible light, ultraviolet rays, x-rays, or gamma rays.
The transfer of heat in this way is known as thermal radiation.

5. Heat Transfer
Some of the heat energy from the sun bounces back off the earth’s atmosphere, but some of it gets through and reaches the earth’s surface.
1. The energy that does reach the earth’s surface warms it.
2. The extra energy causes chemical reactions which give off heat as a by-product.

6. This heat is released through the same process of thermal radiation.
Some of the heat energy is trapped by the greenhouses gases in atoms, and the temperature of the earth rises.

7. The heat source for our planet is the sun.
1. Energy from the sun is transferred through space and the earth’s atmosphere to earth.
2. Some of this energy is heat energy.

8. Radiation
Radiation is the transfer of heat energy through space by electromagnetic radiation.

9. What are 2 examples of radiation?
1. Feeling warm by sitting near a fireplace.
2. Keeping food warm under heat lamps.

10. Radiation
Most of the electromagnetic radiation comes to the earth from the sun in the form of visible light which occurs at many frequencies. These different frequencies are interpreted into colors; red, orange, yellow, green, blue, indigo, and violet.

11. Lower frequency waves show red.
Higher frequency waves show violet.

12. Conduction
Conduction is the transfer of heat from one substance to another or within a substance.
Example:
A metal spoon getting hot sitting in a pot on the stove.

13. Conduction 2 Good Conductors 1. Copper 2. Silver 2 Poor Conductors
1. Wood
2. Plastic

14. Convection
Convection is the transfer of heat energy in a fluid.

15. What is happening in the process of convection?
The sun’s radiation strikes the ground, thus warming the rocks, as rock temperature rises due to conduction, heat energy is released into the atmosphere, forming a concentration of air warmer than surrounding air. This warm air rises. As it rises, it cools and will then sink because it is more dense.

16. One Example of Convection
Heat allowing a hot air balloon to rise.