Key Idea.
Section 1
Energy Turns Water into Gas
Phase changes are driven by energy. When liquid water absorbs energy from the sun, its molecules speed up and escape into the air.
This process is called evaporation. It transforms visible liquid water into invisible water vapor, a gas that rises into the atmosphere. This is the primary way water enters the air.
Section 2
Cooling Air Forms Clouds
The reverse process happens when energy is removed. As an air parcel rises and cools, the water vapor inside it loses energy and slows down.
It eventually changes back into liquid water through condensation. These billions of tiny liquid droplets cluster together to form a visible cloud. Thus, a cloud is evidence of cooling air.
Section 3
Energy Transfers for Equilibrium
Temperature changes in the atmosphere are driven by energy transfer. Energy always flows from warm areas to cool areas in an attempt to equalize the temperature.
When warm, moist air meets cooler surrounding air, energy leaves the warm parcel. This loss of energy is the trigger for phase changes like condensation.
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Section 1
Energy Turns Water into Gas
Phase changes are driven by energy. When liquid water absorbs energy from the sun, its molecules speed up and escape into the air.
This process is called evaporation. It transforms visible liquid water into invisible water vapor, a gas that rises into the atmosphere. This is the primary way water enters the air.
Section 2
Cooling Air Forms Clouds
The reverse process happens when energy is removed. As an air parcel rises and cools, the water vapor inside it loses energy and slows down.
It eventually changes back into liquid water through condensation. These billions of tiny liquid droplets cluster together to form a visible cloud. Thus, a cloud is evidence of cooling air.
Section 3
Energy Transfers for Equilibrium
Temperature changes in the atmosphere are driven by energy transfer. Energy always flows from warm areas to cool areas in an attempt to equalize the temperature.
When warm, moist air meets cooler surrounding air, energy leaves the warm parcel. This loss of energy is the trigger for phase changes like condensation.
Book overview
Jump across lessons in the current chapter without opening the full course modal.
Continue this chapter