Pre-lesson assignment (Diver’s Nightmare)
1)Describe what atmospheric pressure is and the common units it is
measured in. Show the conversion of the units for pressure.
:The gases in the atmosphere exert a force or weight uniformly on all
surfaces,the resulting pressure is called atmospheric pressure.It
common units are atmosphere(atm), pascal(Pa), milimeters of
mercury(mmHg), torr, pounds per square inch(Ib/in2 or psi)& bar.
1tor=1mmHg=1/760atm=101.325/760kPa=133.322Pa
2)What is partial pressure?
:Partial pressure is the portion of the total pressure contributed by a gas
in a mixture of gases.
3)List the types and amounts (volume %) of the four most abundant
gases in the atmosphere, excluding water. Calculate partial pressure
of O2 (g) and N2 (g) in atmospheres.
: Nitrogen-78%
Oxygen-21%
Argon-0.93%
Carbon dioxide-0.039%
Partial pressure for oxygen=1atm*(21%/100%)
=0.21atm
Partial pressure for nitrogen=1atm*(78/100)
=0.78atm
4)How does gas molecules or atoms exert pressure?
:The gas molecules or atoms collide with each other and also with the
surface of everything continuosly.When a molecule collides, it will exert
a small force.The sum of all the collision forces is the pressure exerted
by the gas.