1. WATER IN THE AIR

2. Investigation 6- Water in the Air
Enduring Understanding:
Humidity is the water vapor in the air
Learning Goals:
I will use ice water to cool air to produce condensation.
I will measure changes in temperature due to evaporation.
I will determine dew point by cooling water in a container until condensation occurs on the container.
I will observe changes in temperature due to pressure change.
I will use pressure to produce a cloud in a bottle.
I will explain how dew and clouds form when humid air cools to its due point and condenses.
I will predict could formation by analyzing radiosound sound data.

3. QUESTION
Now we know water vapor is in the air.
How does water vapor get into the air though?

4. CUP DEMONSTRATION (RESEARCH)
Dampen a small area on the back of both hands.
Gently blow on the wet spot on your left hand to simulate wind.

5. RESEARCH What effect does wind have on the wet spot?
Where did the water go that was on your hands?
Why did the wet spot feel cold?

7. Materials Available Cup of water Two pieces of muslin Two Thermometers
Two rubber bands
A paper towel (from the sink area)

9. RESULTS
Water can change from a liquid to vapor only when energy is available.
Evaporation requires energy.
Energy in the form of heat in the environment is usually the source of energy to make evaporation happen

10. Condensation= when water changes from a gas to a liquid.
WORD BANK
Condensation= when water changes from a gas to a liquid.

11. WORD BANK
Evaporation= process where liquid water becomes a gas called water vapor.

12. HUMIDITY Water vapor in the air is called humidity.
When there is a lot of water vapor in the air, the air is humid. Humid air usually makes you feel sticky.

13. HUMIDITY
The amount of water vapor in the air changes as the temperature changes.
The warmer the temperature, the more water vapor the air can hold. As air gets colder, it holds less water vapor.

14. HUMIDITY
When air contains as much water vapor as it can, it is saturated. It takes a lot of water vapor to saturate warm air, but only a little bit of water vapor to saturate cold air.

15. RELATIVE HUMIDITY
Meteorologists often describe the amount of water vapor in the air in terms of relative humidity.
Relative humidity is measured in percentages. Relative humidity compares the amount of water vapor in the air to the amount of water vapor needed to saturate the volume of air.

16. RELATIVE HUMIDITY
You might hear that the humidity today is 50%. That means that the air contains 50% of the amount of water vapor needed to saturate the air at today’s temperature.
For example, 1kg of air at 25 degrees C can hold 20g of water vapor. If it’s holding 10g of water vapor, the relative humidity is 50%