1. Agenda : Water in the Air
- Water Cycle
- Humidity
- Condensation
- Dew Point Lab
TN STANDARD: Analyze and interpret data from weather
conditions, weather maps, satellites, and radar
to predict probable local weather patterns and conditions.

2. SOMEONE SAW A SNOWFLAKE
IN PORTLAND!

3. What is Weather? How does weather affect your daily life?
The condition of the atmosphere at a certain time and place.
Affected by amount of water in the air
To understand weather, you need to understand how water cycles through Earth’s atmosphere.

4. THE WATER CYCLE
For millions of years, WATER in whatever form, is constantly being recycled through the water cycle.
The water cycle is the continuous movement of water from sources on Earth’s surface - such as lakes, oceans and plants - into the air, onto and over land, into the ground, and back to the surface.
Can you name the 4 stages of the water cycle?

5. THE WATER CYCLE
Evaporation occurs when liquid water changes into water vapor, which is a gas.
Condensation occurs when water vapor cools and changes from a gas to a liquid. Clouds form by this process.
Precipitation occurs when the rain, snow, sleet, or hail falls from the clouds onto Earth’s surface.
Runoff is water, usually from precipitation, that flows across land and collects in rivers, streams, and eventually the ocean.

6. What is the water cycle?
Rain bump another neighbor to answer…

7. HUMIDITY
As water evaporates from lakes, oceans and plants, it becomes water vapor - invisible moisture in the air
The amount of water vapor in the air is humidity
As water evaporates & becomes water vapor, humidity increases
As temperature of air increases, air’s ability to hold water vapor increases

8. RELATIVE HUMIDITY
Relative humidity - the amount of water vapor in the air compared with the maximum amount of water vapor that the air can hold at a certain temperature
Relative humidity is given as a percentage
When air holds all the water that it can at a given temperature, it is said to be saturated
Saturated air has a relative humidity of 100%
Two factors that affect relative humidity are:
amount of water vapor and temperature

9. MEASURING RELATIVE HUMIDITY
A psychrometer is an instrument that is used to measure relative humidity.
Consists of two thermometers:
1. wet-bulb thermometer - covered with a damp cloth
2. dry-bulb thermometer
Difference in temperature readings between the 2 thermometers indicates the amount of water vapor in the air.

10. CONDENSATION
Have you ever seen water droplets form on the outside of a glass of ice water? Where did those water droplets come from?
The water came from the surrounding air, and droplets formed as a result of condensation.
Condensation is the process by which a gas, such as water vapor, becomes a liquid.
The air has to be saturated before condensation can occur.
Thinking back to relative humidity, do you remember what the % must be for saturation take place?

11. DEW POINT
Before Condensation can occur, the air must be saturated, which means that the air must have a relative humidity of 100%
Condensation occurs when saturated air cools
Air can become saturated when water vapor is added to the air through evaporation. Air can also become saturated when it cools to its dew point
The dew point is the temperature at which a gas condenses into a liquid
The ice in the glass of water causes the air surrounding the glass to cool to its dew point
Before water vapor can condense, it must have a surface to condense on like the outside of the glass

12. Answer the following questions
What is weather?
What are the 4 stages of the water cycle?
Humidity is the amount of _____________in the air.
When the temperature of the air cools to its___________, the air has reached saturation & condensation occurs.

13. Dew Point & Relative Humidity
Study Jams water cycle
Crash Course Kids
Teacher demo
Meteorologist
Dew Point
Storm Shield
Dewpoint
Dewpoint illustration
STANDARD: Interpret meteorological data to make predictions about the weather

14. Dew you get the Point? Dew Point Lab
Choose a Lab partner to share materials and complete lab sheet
You will need:
Lab sheet (one for each partner)
Tin can filled halfway with tap water
Glass thermometer
Apron for each person
Cup of ice cubes
Stopwatch

15. Directions – Experiment #1
We are measuring the dew point, which is the temperature the AIR must be cooled for the water vapor to condense to a liquid.
We will determine the dew point of the air in our classroom.
Fill can halfway with tap water
Record temperature of water in can
Record ROOM TEMPERATURE on wall thermostat
Observe the sides of the can, brush finger lightly across checking for moisture
PREDICT: Based on the water’s temperature, what degree do you think the air has to be cooled to form condensation? How long do you think this process will take?
Starting stopwatch, slowly add several ice cubes. Stir gently
Observe evidence of moisture forming on outside of can
Brush finger lightly across to check.
Record temperature and time DEW POINT occurred

16. Directions - Experiment #2
Empty can, rinse and fill again halfway with tap water
Refill supply of ice if needed
Record temperature of water in can
Place can near portable heater and record temperature of area near heater
Repeat previous steps: Predict time and temperature of dew point (water vapor beside can will condense to a liquid)
Slowly add ice cubes, observing evidence of moisture on side of can
Record time and dew point temperature

17. Conclusion What was the independent variable in our experiments?
What was the dependent variable?
How did the heat affect outcome?
Was the dewpoint different for each experiment or the same?
Were your predictions correct?
MAKE SURE YOUR INFO IS COMPLETE AND BOTH PARTNERS NAMES ARE ON THE LAB SHEET