1. Aim: How does measuring air pressure tell us about the Weather?
Do Now: Answer the following questions in your notebook.
1. What happens to the air molecules when heat is added?
2. How does adding heat to the air change the density?
3. How does adding heat to the air change the air pressure?
4. What would happen to the air molecules if heat were to be removed?
5. What substance can be added to air to make it less dense?

2. What happens to the air molecules when heat is added?
2. How does adding heat to the air change the density?
3. How does adding heat to the air change the air pressure?
4. What would happen to the air molecules if heat were to be removed?
5. What substance can be added to air to make it less dense?
They move faster and spread out
The air become lighter (less dense)
Since the air is less dense and rising it creates less pressure
They would move slower, their density would increase and the air would sink
WATER VAPOR!!!!!!!!!!!!!!!!!!!!!!!

3. warm air = less dense therefore, less pressure
I. Air Pressure
- the pressure exerted by the weight of air (molecules)
Warm Air Cold Air
warm air = less dense therefore, less pressure
cold air = more dense therefore, more pressure
How does the density of cold and warm air differ? How does this affect the pressure

4. II. Temperature Changes Air Pressure
SINKS
RISES
What type of pressure does warm and cold air create?
Cold air
- More dense causing the air to sink (high pressure).
B. Warm air
- Less dense causing the air to rise (low pressure).

5. III. Measuring Air Pressure
What instrument measures air pressure?
barometer
As air pressure increases the liquid rises in the barometer.
As air pressure decreases the liquid lowers in the barometer.
What can be added to the air to make the air pressure decrease?
water vapor makes air less dense.

6. What would the barometer show us about these two different types of air?
A decreasing barometer (low pressure) means the weather will be cloudy and wet.
An increasing barometer (high pressure) means the weather will be dry and sunny.
WET
DRY
List some of the difference between these two pictures (think about the information we have discussed so far)

7. What can we label the purple arrow in this picture?
IV. Winds
- Differences in air pressure creates wind.
Air moves from high pressure areas to low pressure areas (H L).
WIND
What can we label the purple arrow in this picture?

8. Closely spaced isobars indicate high winds (steep gradient)
V. Pressure gradient:
- Drawn using isobars. (just like contour lines!)
Closely spaced isobars indicate high winds (steep gradient)
Widely spaced isobars indicate light winds (gentle gradient)

9. On which side of the country would the strongest winds exist?
What do you look for to answer this question?

10. Barometric Pressure Reading for March 31 2017 (Friday)
Closure 1:
Barometric Pressure Reading for March (Friday)
High pressure = happy weather (rising barometer)
Low pressure = lousy weather (falling barometer)
Using the chart above, describe; 1) how the chart shows the weather was nice in the morning? 2) how the chart shows the weather was bad during the evening? 3) What changed in the air?
1) Pressure was high (rising) from midnight to 6am
2) Pressure was low (falling) from 7an- midnight.
3) More water vapor was entering the air, making the pressure decrease and causing lousy weather.

11. Closure 2:
From the back table, take the worksheet on pressure and complete this working with your partner.