Unit 7 -Absolute Temperature
 The
kinetic theory of gases relates the absolute
temperature of a gas to the average kinetic energy
of its molecules or atoms.
KE = ½ (mass)(velocity)2
The faster the molecules move, the more the
kinetic energy they have, and thus the higher
temperature the substance has.
Absolute temperature is based on the idea that
at some temperature, all kinetic motion will stop.
This is known as absolute zero
Kelvin Temperature Scale

The Kelvin temperature scale was created to eliminate
negative temperature values.
 0 degrees Kelvin is considered absolute zero, or
where there is no molecular motion.
There is no temperature lower than 0 Kelvin, and
we can never get to 0 Kelvin.

0 Kelvin = - 273 oC
Kelvin = oC + 273
***All temperatures must be in the Kelvin temperature
scale when using the gas laws!
 Absolute
Zero video clip
P
-273oC
Temperature , oC
Charles’ Law
Volume and Temperature

The volume and the temperature of a gas are
directly proportional when the pressure and
number of moles remain constant.
V1 = V2
T1
T2
V
T (K)
 Temperature
is in Kelvin.
K = oC + 273
Charles’ Law
Charles’ Law Video
Sample Problem
The volume of a bubble is 1.5 liters. If its temperature
increases from 20 to 50 oC, what is its final volume?
V1
T1
=
V2
V1 = 1.5 L
T1 = 20oC
T2
V2 = ?
T2 = 50oC
First convert Temperatures to Kelvin!!!!
T1 = 20 + 273 = 293 K
T2 = 50 + 273 = 323 K
1.5 L
293K
=
V2
(293K)V2 = (1.5L)(323K)
323K
V2 = 1.65 L
Guy – Lussac’s Law
Pressure and Temperature
 The
pressure of a gas is directly
proportional to its temperature (when
volume and the number of moles
remain constant).
 P1 = P2
P
T1 T2
T (K)
 Temperature
in Kelvin
K = oC + 273
Sample Problem
 If
a child has a rigid ball with 25 atm of
pressure at 22 oC, what will the
pressure be at 0 oC?
P1 = P2
T1 T2
P1 = 25atm
P2 = ?
T1 = 22oC
T2 = 0 o C
First Convert Temperature to Kelvin!
T1 = 22oC + 273 = 295K
T2 = 0 oC + 273 = 273K
25 atm =
295K
P2
273K
P2(295K) = (25atm)(273K)
P2 = 23.1 atm
Why we can’t get to Absolute Zero