Water’s Changes of State WATER is the most important gas when it relates to weather processes! Who is Stan Hatfield and Ken Pinzke

Mr. Fetch's Earth Science Class Moisture: Change of State MELTING Uses Heat FREEZING Gives off Heat Sublimation Deposition EVAPORATION Uses Heat CONDENSATION Gives off Heat Energy is absorbed or released during a change in state. This is called LATENT HEAT. Mr. Fetch's Earth Science Class

Changes of state of Water Heat absorbed Heat released

What happens to molecules and heat during a change of state? Heat absorbed = molecules move apart (density decreases) Heat released = molecules move closer (density increases)

What are humidity and saturation? Humidity = amount of water vapor in air Saturation = when air holds the most water vapor possible depends on temperature and pressure example: warm air holds MORE water than cold air!

Mr. Fetch's Earth Science Class Warm air holds more moisture than cold air. Mr. Fetch's Earth Science Class

What is relative humidity? Relative Humidity = ratio of air’s actual water content v. air’s capacity (saturation) RH = actual content X 100 capacity

What can change the relative humidity of air? It can be changed by adding or removing water vapor If the water vapor is kept constant Temperature relative humidity Temperature relative humidity

What is Dew Point?  Dew Point The temperature at which water vapor turns to liquid High dew points indicate moist air Low dew points mean dry air.

Dew on a Spider Web Makes no sense without caption in book

Measuring Humidity A hygrometer is an instrument to measure relative humidity. A psychrometer is a hygrometer with dry- and wet-bulb thermometer. Water evaporates from the wet bulb and the air temperature appears lower than the dry bulb. The two temperatures are compared to determine the relative humidity.