The Gas Laws
What are the Gas Laws?

The gas laws deal specifically with volume,
temperature, and pressure.

Changes in volume, temperature, and
pressure have predictable effects on the
behavior of gases

Volume, Temp., Pressure, and the # of
particles in a container of gas all affect one
another
Pressure
 Pressure
is the result of a force distributed
over an area
 Pressure
(atm)
is measured in atmospheres
 Collisions
between particles of a gas and
the walls of the container cause the
pressure in a closed container of gas
Pressure in Airplanes

Before an airplane takes off, the plane must
regulate its air pressure inside the cabin

As the airplane takes off higher into the sky,
the pressure on the outside of the plane is too
dangerous, so the cabin must keep a safe,
regulated air pressure sealed inside

A difference in pressure is also why your ears
“pop”
Factors that affect gas
pressure
 Factors
that affect the pressure of an
enclosed gas are its temperature, its
volume, and the number of particles
 Remember:
in a gas the particles are
constantly moving and bumping into one
another
Temperature
 The
constant motion of particles in a gas
cause the gas to heat up, this is due the
gas’ kinetic energy.
 As
temperature rises, the average kinetic
energy of the gas particles also increases
Temperature cont.
 The
increase in the number particle
collisions, along with the increase in the
force of the collision causes an increase in
pressure within the container
 Raising
the temperature of a gas will
increase its pressure if the volume of the
gas and the number of particles are
constant (Stay the same)
Volume
 As
the volume in a container of gas is
decreased, particles of trapped air start
to collide more often with one another
and the container’s walls
Volume cont.
 Reducing
the volume of a gas increases
its pressure, as long as the temperature of
the gas and the amount of gas particles
remains constant (stays the same)
Number of Gas Particles
 When
you add more gas particles to a
container of gas, the pressure will start to
increase
 Think
about adding more air to a balloon
that is already full, the pressure increases
and eventually the balloon will pop
Number of Gas Particles Cont.
 Increasing
the number of particles in a
container of gas will increase the pressure
of the gas, as long as the temperature
and volume remain constant (stays the
same)
Charles Law
 Named
after French, physical scientist
Jaques Charles.
 His
 He
inventions include the helium balloon
is also known for his study on how
gases behave
Charles Law cont.
 Charles
law states:
“The volume of a gas is directly proportional
to its temperature (in kelvins, k) if the
pressure and the number of particles of a
gas are constant.”
Charles Law cont.
 To
convert Celsius to Kelvin, simply add
273 to the temperature in Celsius
 Example:
30°C = 273+30 = 303°K
Charles Law cont.
 The
this:
equation for Charles Law looks like
Boyle’s Law
 Robert
 He
Boyle was an Irish scientist
was the first to describe the
relationship between the pressure and
volume of a gas
Boyle’s Law cont.
 Boyle’s
Law states:
“The volume of a gas is inversely
proportional to its pressure if the
temperature and number of particles in a
gas remain constant.”
Boyle’s Law
 Boyles
Law is expressed like this:
The Combined Gas Law
 The
relationships described by Boyle’s Law
and Charles’ Law can be described by a
single law
 As
long as we know the number of
particles remains constant, we can use
the combined gas law
The Combined Gas Law cont.
 The
Combined Gas Law looks like this:
Combined Gas Law cont.
The Ideal Gas Law
 Now,
all this math and chemistry is
probably making your brain want to
explode
 Good
news, there is a simpler gas law!
The Ideal Gas Law
 The
Ideal Gas Law looks like this
PV
= nRT





R = 0.0821
P = Pressure
V = Volume
T = Temperature
n = number of moles in a substance
What is R?
R
will always be 0.082, it’s a constant
Crash Course, IGL
 Crash
Course