Download 12.1 NOTES Where does water in the atmosphere come from

12.1 NOTES
Where does water in the atmosphere come from?
Objective: Explain how water gets into the atmosphere
Water in air is in the form of a gas called water vapor. Water changes state at
ordinary temperatures and pressures, allowing water to leave the oceans as a gas
and returning again as a liquid. Water is also found in the atmosphere as clouds
and fog. These are made up of tiny droplets of water or ice.
The amount of water vapor in the air differs from place to place over time.
Evaporation occurs when a liquid changes into a gas. Most of the water in the air
evaporates from the oceans. Water also evaporates from lakes, pond, rivers,
puddles, and soil. Winds carry this water vapor all over Earth’s surface.
Molecules in liquid are
always moving. When a
liquid is heated, its
molecules move faster,
allowing more to escape
from the surface.
Evaporation from the
oceans occurs most rapidly
around the equator where
the water receives more
direct rays from the Sun.
Living things add water vapor to the air through respiration. Plants also give off
water vapor through a process called transpiration. This occurs in the leaves of
plants through tiny openings called stomata.