Charles’ Law
Charles’ Law
discovered
by
French physicist,
Jacques Charles
in 1787
first
person to
fill balloon with
hydrogen gas
and make solo
balloon flight
Temperature vs. Volume
If P is constant, gases expand when
heated.
When T increases, gas molecules move
faster and collide with the walls more
often and with greater force.
To keep the P constant, the V must
increase.
Charles’ Law: T and V
Charles’
Law states that the
volume of a fixed mass of gas
varies directly with temperature at
a constant pressure.
V
= kT or k = V/T
k
is a constant for a certain
sample of gas that depends on the
mass of gas and its pressure.
What
kind of graph is V vs. T?
Charles’ Law
If
we have a set of new
conditions for the same
sample of gas, they will
have same k so:
 V1/T1 =
k = V2/ T2
 V1/T1 =
V2/ T2
PROBLEM…
If
we use the Celsius
temperature system,
we could end up with
negative values when
using Charles’ gas
law.
SOLUTION…
To
use Charles’ Law we need a
temperature scale that has no
negative values; this is the Kelvin
Temperature Scale.
starts at -273.15 ° C =
absolute zero = 0 Kelvin (K)

The lowest possible
temperature for this system is

Example: Charles’ Law

A gas with a volume of 600 mL has a
temperature of 30 0C. At constant pressure
the gas is heated until the gas expands to
1,200 mL. What is the new temperature of
the gas if the pressure remains constant?
SOLUTION
1.
2.
3.
4.
The first step is to convert the temperature
from Celsius to Kelvin: 273 + 30 = 303 K
Rearrange Charles’ law to solve for the
new temperature: T2= V2 T1 / V1
T2 = 1200mL X 303 K = 2 X 303K =
600mL
T2 = 606K