PROPERTIES
OF GASES
II
PRESENTATION 2
2014
Properties of Gases
1. Gases have mass – find mass of empty balloon
2.
3.
4.
5.
6.
and filled balloon
It is easy to compress gases – squeezed gas
reduces its volume; car air bags
Gases fill their containers completely –
Different gases can move through each other quite
rapidly – diffusion (body spray, body gas, etc)
Gases exert pressure – ear drums “popping”,
filled balloon
The pressure of a gas depends on its temperature
↑ temp = ↑ pressure; ↓ temp = ↓ pressure
Properties of Gases and the Air
we Breathe
 How will we do it:
 Main Ideas
(in no order):
 Atmospheric
 Notes
Pressure
 Volume
 Temperature
 Kinetic
Molecular
Theory
 Composition of Air
 Labs
and Activities
 Worksheets
 Practice Problems
and Questions
MEASURING GASES
 Four Variables:
Amount
of gas
Volume
Temperature
Pressure
AMOUNT OF GAS (n)
 Quantity of gas in a given sample is
expressed in terms of moles of gas
n =mass
= m (g)____
molar mass M (g/mol)
One mole of NaCl,
= mass of 58.45 g.
One mole of the liquid,
= mass of 18.0 g and
occupies a volume of
18.0 mL.
One mole of the gas,
= mass of 32.0 g and
occupies a balloon
whose diameter is 35 cm
VOLUME (V)
 Gas uniformly fills any container in
which it is placed
 Volume of gas = volume of its container
 Metric unit = L
1
L = 1000 cm3
TEMPERATURE (T)
 Measured with thermometer in degree
Celsius (˚C)
 Must be converted to Kelvin temp scale

No negative temps
T
(K) = T (˚C) + 273
PRESSURE (P)
 Outward force of gas spread over the
area of the container is called pressure
 P = Force
Area
Pressure =
Pascal (Pa)
ATMOSPHERIC PRESSURE
 Gases of atmosphere also exert pressure on
everything come into contact with
(gas) density = Mass (of gas)
Volume
P=m
V
Atmospheric Pressure decreases with height
Pressure of Atmosphere
 Can Crushing
http://www.youtube.com/watch?v=QVayky_b-6U
 55 Gallon Drum
http://www.youtube.com/watch?v=Uy-SN5j1ogk
Pressure Measuring Devices
 Weather Prediction
 Barometer
 http://www.youtube.com/watch?v=jmQ8FWnM0fA&list=RD
QeAp3CuGjk8
 Regulation of gas flow
 http://www.youtube.com/watch?v=QeAp3CuGjk8
Units of Pressure
1 atmosphere (atm) = 101,325 Pa
1 atm = 760 mm Hg = 760 torr
1 atm = 14.70 lb/in2
1 bar = 100,000 Pa = 0.9869 atm
Sample Problems
 Mercury (Hg) column in barometer is 745 mm above
the mercury reservoir at the bottom. What is the
atmospheric pressure in pascals?
745 mm Hg x 101,325 Pa = 99,300 Pa
760 mm Hg
Practice Problem
The air pressure inside the cabin of an airplane is
8.3 lb/in2 What is this pressure in atmosphere
units?
Practice Problem 2
Pressure is considered the most accurate measure of
storm strength, with lower pressure indicating a
stronger storm. One of the lowest recorded
pressures in the Western Hemispheres is 88.86 kPa.
How high a column of mercury would be balanced by
this atmospheric pressure?
Pressure Conversions
STP means standard temperature and pressure
1 standard atmosphere = 1.000 atm = 760.0
mm Hg = 760.0 torr =101,325 Pa = 14.69 psi
***all of these equal each other!***
Temperature: 0 ˚C or 273 K