Transcript Air Pressure

Air Pressure
Air (barometric) Pressure
• The weight of air pressing down on Earth.
Air Pressure can change from place to
place, and this causes air to move, flowing
from areas of high pressure toward areas
of low pressure. It’s the same as
barometric pressure.
Density
• The measure of how tightly packed the
matter in an object is (hot air and low
pressure= less dense; cool air and high
pressure= more dense)
High Pressure System
• A whirling mass of cool, dry air. Because
cool air is heavy and denser than warm
air, it sinks. High pressure brings fair
weather, sunny skies, light winds, and
stable weather. High pressure systems
rotate clockwise.
High Pressure System
•
The air moving away from the
High pressure system leaves a
"hole" to be filled, so air from
above sinks into that "hole". As
the air sinks, water that was in the
condensed form (like clouds)
tends to evaporate into water
vapor. This means the water is not
in the condensed form needed to
make clouds and precipitation.
That's why many people see a H
on a weather chart and know good
weather and clear skies are
coming!
Low Pressure Systems
• A whirling mass or warm, moist air.
Because warm air is lighter and less
dense than cool air, it rises, and then
cooler air flows in underneath. Low
pressure systems bring storms, strong
winds, and changing, unstable weather,
low pressure systems rotate counterclockwise.
Low Pressure System
• Air moves into a Low pressure
system. It pushes any air that
was there up. As the air rises,
water vapor condenses into
clouds that can bring
precipitation. That's why many
people see a L on weather
chart and know there is a good
chance of "bad" weather cloudy skies and possibilities
of rain or snow.
Oh! The Pressure!
• We live at the bottom
of and “ocean of air”
called the
atmosphere. This
ocean is about 350
miles deep. Most of
the weather you
experience takes
place in the bottom 3
miles of this ocean.
Did You Know…
• Air pressure changes a lot as you go up in
elevation. But, air pressure can change
right here on the ground. Usually changes
in air pressure happen too slowly for most
people to feel. You probably have noticed
something that a change in air pressure
causes- WIND!
Our Experiment!
• We are going to observe what happens to
the air in a bottle when we submerse it in a
tub of cold water and a tub of hot water.
• Put the balloon over the mouth of a bottle.
• Put the bottom of the bottle into the warm
water first. What happens?
• Put the bottom of the bottle into the cold
water. What happens?
Create!
• Create a five-cornered star on the next
available sheet in your science notebook.
• Don’t waste paper! Use fronts and backs!
• Like this:
Conclusion/
Problem/Focus Questions
Why did it happen?
Hypothesis
Results/What happened?
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Materials/
Procedures
Step #1 Problem/ Focus
Questions
What happens to molecules in air when air is
heated?
What happens to molecules in air when air is
cooled?
What does this have to do with weather?
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Step #2 Materials/Procedure
Add the materials/procedures to your star
second! Here’s what you’re going to do:
1. Place the balloon gently over the lip of the
bottle.
2. Place the bottle into a pan of hot water and
observe what happens.
3. Place the bottle into a pan of cold water and
observe.
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Step #3 Hypothesis
• What do you think will happen when you
place the bottle in the hot water?
• What do you think will happen when you
place the bottle in the cold water?
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Step #4 Results/What happened?
• In the “Results” section of your star, tell
what you saw!
• Create a diagram that shows what you
saw, too!
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Step #5 Conclusion/Why did it
happen?
• Was your hypothesis correct?
• Answer the focus questions!
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Video – Explanation
www.discoveryeducation.com
• Watch the video at the link below for more
information about what happens when air
is heated.
• You can change your conclusion based on
this new information, if you like.
• http://player.discoveryeducation.com/index
.cfm?guidAssetId=9760A447-0E1F-4E729C360C2897A108A8&blnFromSearch=1&produ
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ctcode=DSCE
Think about this…
• What happened?
• Why did the balloon Inflate when dipped in
the warm water?
• Why did the balloon Deflate when dipped
in the cold water?
• What does this tell us about air pressure
and how it works?