Water Vapor and Humidity
Main Idea: Water on Earth’s surface and in the atmosphere changes
form and affects the weather
Water Vapor- water in the form of a gas.
o It is invisible, colorless, odorless, and tasteless.
Humidity- the amount of water vapor in the air
o Two factors determine the amount of humidity
1. water available to evaporate
2. the warmer the temperature the faster the water
evaporates.
Evaporation- the changing of a liquid into a gas.
Condensation- the changing of a gas into a liquid.
Relative humidity- comparison between how much water vapor is
in the air and how much the air can hold.
o Affects how you feel
What Happens When Warm, Moist Air Cools?
(3) Things can happen
1. Air can cool by being pushed upward over mountains by winds.
2. Heating the air causes it to rise. When sun heats the ground, air
above the ground warms and rises. When it rises, it expands (gets
bigger) and cools.
3. Air can be pushed up when cooler air and warmer air meet. When
they meet, THEY DON’T MIX. The lighter warmer air is pushed over
the heavier cold air. Because of this, the warm air that was pushed
up into the atmosphere, cools.