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

2. 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

3. Changes of state of Water
Heat absorbed
Heat released

4. 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)

5. 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!

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

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

8. 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

9. 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.

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

11. 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.