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# Air Pressure PowerPoint PPT Presentation

Air Pressure. Elbow Chat. What is weather? Describe the weather today. Write this in your notes!. Weather: condition of Earth’s atmosphere at a particular time and place . It can change day to day. Question:. Does air have mass? Prove it with our balloon lab. Review.

Air Pressure

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### Elbow Chat

• What is weather?

• Describe the weather today.

### Write this in your notes!

• Weather: condition of Earth’s atmosphere at a particular time and place.

• It can change day to day.

### Question:

• Does air have mass?

• Prove it with our balloon lab.

Review

• Air is made of individual molecules that each has their own mass

• Air has mass, which means it has “pressure”.

• Pressure: force pushing on an area

### Air also has DENSITY

• Density – the amount of mass per unit volume

• D = M/V

• As air pressure decreases, the density of air decreases.

### Elbow Chat

• The weight of the column of air above your desk is about the same as the weight of an entire school bus!

• Why does it not crush us?

• The air pressure does not crush us because air molecules push in all directions, not just down on us. So the pressure evens out.

### Elbow Chat

• Observe the device in this picture on the right.

• What do you think this is called?

• What do you think it is used for?

Write Barometer in weather factor chart (3E):

• Barometer: tool used to measure air pressure (AP)

• AP drops – stormy (Low pressure system) aka: Lousy weather

• AP rises – clear (High pressure system) aka: Happy weather

• Listen carefully to the following video. You and your elbow partner will have a few questions to answer at the end.

VIDEO

### Elbow Chat on the Video (answer the questions on your paper in complete sentences)

• 1. What force is pulling air down?

• 2. Can the weight of air change? Explain.

• 3. In which type of temperature (hot or cold) do molecules move faster?

• 4. Which direction does cold air travel (up or down)?

• 5. Does temperature affect air pressure? Explain.

Write everything from now on!

• Gravity

### Can the weight of air change? Explain

• Yes.

• Hot air – lighter Cold air - heavier

• Hot air

### Which direction does cold air travel (up or down)?

• Sinks down because it is more dense

### Does temperature affect air pressure? Explain.

• Yes.

• Hot air rises and cold air comes down to take its place.

• This makes the air move, which causes changes in weather.