1. Elements of Weather Notes
Unit 4

2. What is weather?
Weather is the condition of earth’s atmosphere at a certain time and place

3. What is temperature? Temperature is how hot or cold something is
Measured using a thermometer : Celsius or Fahrenheit
Cold ---contracts, particles closer together
Warm---expands ,particles farther apart

4. What is humidity?
The amount of water vapor (gas) in the air is Humidity.
Relative Humidity: actual amount of water vapor in the air
amount of water vapor the air COULD hold at that temperature
95% Relative Humidity: 95/100 = 95%
10% Relative Humidity: 10/100 = 10%

5. Saturated vs Unsaturated
Saturation means the air is “full” of water vapor
The relative humidity would be 100% (100/100 = 100%)
When air is saturated, the rates of evaporation equals the rate of condensation

6. What are two ways to change the amount of water vapor in the air?
Add more water vapor by evaporation. Relative humidity ____________.
2. Cool the air so that more condenses
Relative humidity
______________.

7. What happens when the temperature cools and there is more condensation than evaporation?
The air reaches its Dew Point: the temperature at which more condensation than evaporation occurs
Gas Liquid
So what do we see???......Dew! Fog! Clouds!
Yes that’s right, a cloud is a liquid!
The bottom of the cloud represents the temperature at which the dew point is reached.

8. Review
As temperatures increase, the rate of _______________increases and therefore relative humidity __________________.
Cooler temperatures ________________ the amount of water vapor that can be in the air and therefore, relative humidity ___________________.
A cloud is a ________________ ( solid , liquid or gas)

9. What is air made up of? Air is particles of matter
You can change the motion of those particles by:
1. Changing Temperature
2. Changing Pressure

10. Demonstrations Plastic container Bottle of water In ice
What part of the box are molecules of air pushing on?
How do we know air is pressing on all sides equally?
What does the bottle look like before the experiment?
What will happen when the bottle with warm water is put in an ice bath?
Why does the shape of the bottle change?
So-the shoe box shows that air pressure acts in all directions.
The bottle shows how changing temperature changes pressure. So they know that cooling, contracts and decreases pressure.

11. What is Air pressure?
Air pressure is the FORCE of air molecules pushing on an area. Air pressure depends on the weight of the air above us.
Why don’t we feel like we are being pressed down by air?
Because the air pushes in all directions, the force of the air pushing down is equal to the air pushing up…lucky for us, on any given day we don’t implode or explode like a plastic bottle!

12. There are two ways to change Air pressure:
Temperature
Altitude
Water molecules that are warm move faster and expand in a container, hitting the walls of the bottle = high pressure
Cooler molecules move slower and don’t hit the walls as much = low pressure
What happens when you take a bottle of water or a bag of chips from Missouri to Colorado?
Pressure decreases as altitude increases
Pressure decreases as you increase altitude if you visualize living in an “ocean” of air. At higher altitudes, you have less air above you and thus less pressure acting on you. At sea level, you are deeper in the “ocean” of air and thus more pressure is acting on you.

13. Changing temperature

14. Changing altitude

15. Lets review High temperature = _______________ pressure
Low temperature = ________________ pressure
High altitude = __________________ pressure