Gas LawsGas Laws

PSquiresPSquires

20112011

Properties of GasesProperties of Gases

Gases expand to fill the container.Gases expand to fill the container. Gases take on the shape of the Gases take on the shape of the

container.container. Gases are highly compressible. Gases are highly compressible.

(Can be liquefied at high (Can be liquefied at high pressure).pressure).

Gases have low densities.Gases have low densities. Gases mix uniformly.Gases mix uniformly.

1. Molecules are in constant random motion1. Molecules are in constant random motion

2. A gas is mostly empty space2. A gas is mostly empty space

Kinetic Molecular Theory

3. No intermolecular forces3. No intermolecular forces

4. Collisions are elastic. 4. Collisions are elastic. No change in energy.No change in energy.

Use Kelvin degrees!Use Kelvin degrees!

Temperature conversionTemperature conversion

K =K = C +C + 273273

Pressure MeasurementsPressure Measurements

Standard sea level pressure is…Standard sea level pressure is…

1.00 atmospheres (atm)1.00 atmospheres (atm)760. mm Hg760. mm Hg760. torr (from Torricelli)760. torr (from Torricelli)101.3 kilopascals (kPa) 101.3 kilopascals (kPa) 14.7 lb/in14.7 lb/in22

Boyle’s LawBoyle’s Law

At constant temperature, pressure is At constant temperature, pressure is inverselyinversely proportional to volume. proportional to volume.

Pre

ssur

e

Volume

Boyle’s LawBoyle’s Law

At constant temperature, pressure is At constant temperature, pressure is inverselyinversely proportional to volume. proportional to volume.

1/P

ress

ure

Volume

Boyle’s LawBoyle’s Law

At constant temperature, pressure is At constant temperature, pressure is inverselyinversely proportional to volume. proportional to volume.

PP11VV11 = P = P22VV22

Boyle’s Law Problem:Boyle’s Law Problem:

PP11VV11 = P = P22VV22

The pressure of some NThe pressure of some N22 gas is gas is

4.53 atm when the volume is 4.53 atm when the volume is 30.0 mL. What is the pressure 30.0 mL. What is the pressure when the volume is increased to when the volume is increased to 150. mL at a constant T?150. mL at a constant T?

Charles’ LawCharles’ Law

At constant pressure, volume is At constant pressure, volume is directly proportional to temp.directly proportional to temp.

Vol

ume

Temperature

Charles’ LawCharles’ Law

At constant pressure, volume is At constant pressure, volume is directly proportional to directly proportional to temperature.temperature.

VV11

TT11=

VV22

TT22

Charles’ Law Problem:Charles’ Law Problem:A quantity of oxygen gas A quantity of oxygen gas has a volume of 50.0 mL has a volume of 50.0 mL at 30.0 C. Find the at 30.0 C. Find the volume of Ovolume of O22 gas when gas when

the temperature is the temperature is increased 150.0 C at a increased 150.0 C at a constant pressure.constant pressure.

VV11

TT11=

VV22

TT22

Combined Gas LawCombined Gas Law

The combined gas law is the The combined gas law is the combination of Boyle’s Law and combination of Boyle’s Law and Charles’ Law.Charles’ Law.

PP11VV11

TT11

=PP22VV22

TT22