1. The Nature of Gases Under Pressure!

2. Gas pressure on Earth is called Atmospheric Pressure.
How is atmospheric pressure measured? (Do you know the instrument name?)

3. Barometers measure atmospheric pressure.
When does atmospheric pressure change?
It changes depending on weather and altitude.

4. Early barometers were a glass tube filled with mercury that was placed in a dish with more mercury.
Draw a picture of a mercury barometer that was placed at the top of Mount Rainier.

5. Are there other ways to measure atmospheric pressure?
At sea level, atmospheric pressure is:
760 mm Hg (millimeters mercury, how many millimeters high the mercury column is on the barometer) – also can use Torr
101.3 kPa (kilopascals, pascal = 1 N/m2)
1 atm (atmosphere)
These are conversion factors to be able to convert from one unit of P to another.

6. So how much pressure are we under?
Earth’s atmosphere is pressing against you with a force of 14.7 pounds per square inch (psi).
Why doesn’t it squash you??

7. Comparing volumes of gases
To compare gas volumes, we use STP – Standard Temperature and Pressure
1 atm pressure and 0°C (273 K)