1. Science We need cotton balls Do Now: 3/12 Can you bring some?
HW: Read 16-1 and study for quiz
1. Clear your table for the quiz
Today
~ TTK 16:1 quiz and check
~ Complete PPT w/notes: Water in the Air

2. The Water Cycle
The transfer of water between the atmosphere and Earth’s surface.
Water evaporates from plants and bodies of water
Water condenses in the atmosphere and forms clouds
Clouds become saturated and water falls as precipitation to the surface
Water runs off surface into lakes, streams and oceans.

3. What is Humidity? The amount of water vapor in the air.
As water evaporates it becomes water vapor.
Water vapor is invisible.
Warm air can
hold more
water vapor

4. What is Relative Humidity?
Amount of water vapor in the air compared to the amount of water the air can hold.
A percentage %
Air holds all the water vapor it can
= Saturated = 100% RH

5. Figuring Relative Humidity
_actual water vapor content (g/m³)__ X 100 = RH
saturation water vapor content(g/m³)
1 m³ of air at 10ºC has 5g of water vapor
but, at this temperature it can hold 8g
Calculate RH g X 100 = 63%
8 g
Air holds 13g but can hold 25g
13 g X 100 = 52%
25 g

6. Factors Affecting Relative Humidity
The amount of water vapor
The temperature
If the water vapor stays the same:
Temperature goes down RH%  up
Temperature goes up RH%  down

7. How does that work??? Temperature ºC Saturated g 15 10 20 25
At 20 ºC with 15g of water vapor RH = 100%
Temperature goes up to 25 ºC air could hold 20g
So…
15g (what it has) X 100 = 75%
20g (what it could have)

8. Measuring Relative Humidity
1. Measured with a psychrometer
2. Has two thermometers
* 1 wet bulb
* 1 dry bulb
Use the dry bulb temp and the chart

9. Determining Relative Humidity
Use your book; page 484
Determine the relative humidity for the following days
Day
DryºC
WetºC
DifferºC
RH %
Mon 16 18
Tue 20
Wed 21

10. Determining Relative Humidity
Day
DryºC
WetºC
DifferºC
RH %
Mon 16 18 2 81
Tue 20 4 63
Wed 21 3 73

11. Condensation 1. Water vapor becomes a liquid
2. Happens when air is saturated
3. Air cools to 100% relative humidity

12. Dew Point
Temperature at which the air is saturated & condensation occurs
Where does the water on the outside of a glass
come from???
The cold liquid in the glass cools the air outside of the glass
Air next to the glass reaches its Dew Point
Water vapor in the air condenses on the glass!
Quick Lab: pg 485
What is the dew point temperature in the classroom today?

13. Clouds A collection on millions of tiny water droplets or ice crystals
Warm air rises  cools to dew point
water vapor condenses to a liquid/solid
Altitude and form/shape

14. Forms of Clouds Cumulus: Fluffy white with flat bottoms
Stratus: Form in layers, cover large
areas of sky
Cirrus: Thin, feathery form at high
altitudes

15. Altitude of Clouds Cirro – forms at high altitude made of ice crystals
Alto – middle altitudes
made of ice crystals & water droplets
Low altitudes have no special prefix