1. By: Group 1 By: Group 1

2. At daytime, sunlight warms the Earth. Through conduction, air near the ground warms up.conduction conduction between the air and the ground

3. Warm air expands and becomes less dense. Expanding air

4. Being less dense than the surrounding air, the warmed air rises … rising air

5. Decreasing air pressure at higher altitudes causes the rising air to expand even more. Decreasing air pressure

6. Expansion causes the rising air to cool. At the same time, the relative humidity(RH) also increases.relative humidity(RH) Cooling of rising air

7. As the air rises, its RH increases. it expands, cools, and

8. At a certain height, the RH of the rising air reaches 100%. The air is now saturated. The resulting condensation of water vapor forms a cloud.

9. References: 1.http://www.mtc.com.my/publication/library/drying/ch21.htmhttp://www.mtc.com.my/publication/library/drying/ch21.htm The source for the hygrometer illustration. Downloaded last February 2003. 2. “Conduction," Microsoft® Encarta® Encyclopedia 2001. © 1993- 2000 Microsoft Corporation. All rights reserved. 3. “Humidity,” Microsoft® Encarta® Encyclopedia 2001. © 1993-2000 Microsoft Corporation. All rights reserved.

10. At daytime, sunlight warms the Earth. Through conduction, air near the ground warms up.conduction Conduction is the transfer of energy between objects in contact due to a difference in temperature. Conduction is the transfer of energy between objects in contact due to a difference in temperature.

11. Expansion causes the rising air to cool. At the same time, the relative humidity(RH) also increases.relative humidity(RH) Relative humidity(RH) is the ratio of the actual water vapor content of air to the water vapor content of air that is saturated with water vapor at the same temperature. When RH is 100%, the air is said to be saturated. RH is measured with an instrument known as a hygrometer (shown here). Relative humidity(RH) is the ratio of the actual water vapor content of air to the water vapor content of air that is saturated with water vapor at the same temperature. When RH is 100%, the air is said to be saturated. RH is measured with an instrument known as a hygrometer (shown here).