Gases expand to fill their container, take the shape of the container, and are highly compressible. Gases have low densities and mix uniformly. According to the kinetic molecular theory, gas molecules are in constant random motion with mostly empty space between them and no intermolecular forces. Boyle's law states that at constant temperature, pressure and volume are inversely proportional. Charles' law says that at constant pressure, volume is directly proportional to temperature. The combined gas law incorporates both Boyle's and Charles' laws.

1. Gas Laws
PSquires
2011

2. Properties of Gases
 Gases expand to fill the container.
 Gases take on the shape of the container.
 Gases are highly compressible.
(Can be liquefied at high pressure).
 Gases have low densities.
 Gases mix uniformly.

3. Kinetic Molecular Theory
1. Molecules are in constant random motion
2. A gas is mostly empty space
3. No intermolecular forces
4. Collisions are elastic. No change in energy.

4. Use Kelvin degrees!
K = C + 273
Temperature conversion

5. Pressure Measurements
Standard sea level pressure is…
1.00 atmospheres (atm)
760. mm Hg
760. torr (from Torricelli)
101.3 kilopascals (kPa)
14.7 lb/in 2

6. Boyle’s Law
Pressure
Volume
At constant temperature, pressure is inversely
proportional to volume.

7. Boyle’s Law
1/Pressure
Volume
At constant temperature, pressure is inversely
proportional to volume.

8. Boyle’s Law
At constant temperature, pressure is inversely
proportional to volume.
P1V1 = P2V2

9. Boyle’s Law Problem:
The pressure of some N2 gas is
4.53 atm when the volume is
30.0 mL. What is the pressure
when the volume is increased to
150. mL at a constant T?
P1V1 = P2V2

10. Charles’ Law
Volume
Temperature
At constant pressure, volume is
directly proportional to temp.

11. Charles’ Law
At constant pressure, volume is
directly proportional to
temperature.
V1 V2
T1 =T
2

12. Charles’ Law Problem:
A quantity of oxygen gas
has a volume of 50.0 mL
at 30.0 C. Find the
volume of O2 gas when
the temperature is
increased 150.0 C at a V1 V2
constant pressure. T = T2
1

13. Combined Gas Law
The combined gas law is the
combination of Boyle’s Law and
Charles’ Law.
P1V1 P2V2
=
T1 T2