SCIENCECHAPTER 6 WEATHER

SECTION 1WATER IN THE AIR

PG 170-177

Weather• Condition of the atmosphere at a given moment.

(What is it like outside right now?)

Water Cycle•Water cycles through Earth’s atmosphere.

Water Cycle•Evaporation – water changes into water vapor (evaporates)•Condensation – water vapor changes from a gas to liquid (condenses)•Precipitation – liquid and/or frozen water falls from the sky•Runoff – water moves around Earth

Humidity•Humidity is the amount of water vapor in the air.

•As water evaporates, humidity of air increases

•Air with a higher temperature can hold more water vapor.

•Air that can’t hold any more water is saturated.

•Saturated air has 100% relative humidity

Factors Affecting Relative Humidity1) Changes to amount of water vapor in air

adding more water vapor increases relative humidity

2) Increase or Decrease of Air TemperatureAir that is colder has a higher relative

humidity Air that is warmer has a lower relative

humidity

Condensation•Process when water vapor changes into a liquid•Air must be saturated for condensation to occur.•Must be a surface for condensation to occur.

Dew Point•The temperature at which water vapor condenses to a liquid

Clouds•A collection of millions of tiny water droplets.

•Clouds are classified by form and altitude.

Precipitation•Water falls back to Earth as a liquid or solid.•Tiny water droplets combine to form a rain drop.•When the rain drop is too heavy, it falls.