Name
Lab Day
Charles’ Law
Introduction:
Matter in the gaseous state consists of molecules which are far
apart and in constant motion; their speed or molecular motion is directly
related to the temperature of the gas. From everyday life, when a gas is
heated, it expands and when cooled, the volume decreases. Tire inner
tubes and balloons are common objects which will readily show this
change in volume according to changes in temperature. The law of
Charles expresses this relationship between the volume of a given mass
of gas and the temperature, where the pressure is constant. Charles’ law
may be expressed as:
V  T or V = kT
Where V is the volume, T is the Kelvin temperature, and k is a
proportionality constant. If the volume of the same sample of gas is
measured at two temperatures, then solving for k gives:
k=
V
V
V
= 1 = 2
T
T1
T2
or
V2 =
V1 × T2
T1
The general plan of this experiment is to determine the amount of
contraction of the air in a flask when the temperature changes from that
of boiling water to that of a cold water bath (or ice water).
Procedure:
Set-up the apparatus shown below:
You can replace
the burner, wire
gauze, and ring
with a hot plate
2
The inside of the flask must be thoroughly dry. Insert the stopper and
tube, then mark the lower level of the stopper with a wax pencil. Now,
follow the following steps:
1.
Heat the water in the beaker to boiling and continue heating
it for about 10 minutes. You may assume that the air in the
flask is now the same temperature as the boiling water.
Record this temperature on the data sheet.
2.
While the flask is still in the boiling water, seal it by
clamping the rubber tubing tightly with a screw or pinch
clamp. Remove the flask from the boiling water bath and
invert it in a trough of cold water. Remove the clamp, letting
cold water flow into the flask. Submerge the flask, and keep
it submerged for at least 10 minutes, weighing it down if
necessary.
3.
Record the temperature of the cold water used to cool the
flask on the data sheet. Equalize the pressure within the
flask with the atmospheric pressure by raising the flask until
the water levels inside and outside the flask are the same.
Pinch the rubber tubing to close the flask. Remove the flask
from the cold water and set it upright on your lab bench.
4.
Remove the stopper assembly. Use your graduated cylinder
to carefully measure the volume of water that flowed into the
flask.
5.
Fill the flask to the wax pencil mark with water. Measure the
total volume of water in the flask.
6.
Repeat steps #1 – #4 again for a second trial (if you use a
different flask, you will also need to do step #5 again).
3
Name
Date
Report for Charles’ Law Experiment:
Data:
Run 1
Run 2
1. temperature of boiling water
K
K
2. temperature of cold water
K
K
3. volume of water collected in flask
mL
mL
4. volume of air at higher temperature
mL
mL
5. volume of air at lower temperature ( #4 – #3)
mL
mL
Calculations:
6.
Step #5 above is the actual volume of the cooled air. Calculate the
theoretical volume using Charles’ law:
Vcool air =
7.
Vhot air × Tcool air
Thot air
What is your percentage error?
% error =
Vtheoretical - Vactual
× 100 =
Vtheoretical
Vstep#6 - Vstep#5
Vstep#6
× 100