Measuring Pressure

Unit 2 Worksheet 2 - Measuring Pressure
Problems 1 and 2. Calculate the pressure of the gas in the flask connected to the
The pressures
are equal.
3. What do we mean by atmospheric pressure? What causes this pressure?
Atmospheric pressure is the force per unit area exerted on a surface due to the weight of
air molecules above it. It is caused by the collisions of the air molecules with that surface.
4. How do we measure atmospheric pressure? Is atmospheric pressure the same
everywhere on the surface of the earth?
We measure atmospheric pressure using a barometer – the height of a column of mercury
indicates the pressure exerted by the air. It is not the same everywhere because
temperatures and altitudes are different.
5. Why is the fluid in a barometer mercury, rather than water or another liquid?
Atmospheric pressure would support a column of water roughly 10 m high. Because
mercury is more than 13 times as dense as water, the column of mercury in a barometer is
less than one meter high.
6. Explain why you cannot use a pump like the
one at the right to lift water up to the 3rd floor of
an apartment complex.
This type of pump works by removing air above the
column of water in the pipe. As the pressure above
the water is reduced, the surrounding air pushes
the water up the pipe. The maximum height of a
column of water supported by air pressure is about
10 m.
7. One standard atmosphere of pressure (SP) is equivalent to
760 mmHg.
8. Convert pressure measurements from one system of units to another in the
following problems.
1 atmosphere = 760 mmHg = 14.7 psi (pounds per square inch)
a. 320 mmHg
b. 30.0 psi x
c. The barometric pressure in Breckenridge, Colorado (elevation 9600 feet) is
580 mm Hg. How many atmospheres is this?