LAB: Charles’ Law
Background: In this experiment you will check the validity of Charles Law by measuring
the volume of a sample of air at two different temperatures. Using Charles Law you will
predict the volume the gas should be at the lower temperature based on its volume at the
higher temperature. Then you will compare the predicted volume at the lower
temperature with the actual measured volume . Since Charles law predicts the ratio of
volume to temperature is constant, you will also calculate the volume to temperature
ratios for the two temperatures and see if they agree.
Suggested Materials:
Balloon
Thermometer
String
Hot-plate
Beakers of appropriate size
Problem: Design an experiment to test Charles’ law at the freezing point and boiling
point of water.
Pre-Lab:
1. Write the formula for Charles’ Law and state the relationship between volume and
temperature.
2. What gas variables are constant in your procedure?
3. Would you expect different results if you performed the procedure in Denver
where the atmospheric pressure is much less than in Simi Valley.
Experimental Procedure: Devise and write a step by step procedure to test Charles Law
to see how temperature affects the size of the balloon.
Data:
Ice bath
Room temperature
Steam
o
Temperature C
Temperature K
Calculated Volume cm3
Circumferance cm
Radius cm (from circ.)
Measured Volume cm3
Mass balloon empty (g)
Mass balloon full (g)
Calculations: Show your calculation set-up for the above table.
Graph: Create a line graph of volume (cm3) vs Temperature (K). Plot both your
measured and predicted volumes with 2 different lines.
Post-Lab
1. How did the circumference of the balloon change with the changing temperature?
2. Did your experimental volumes match your predicted values? If not explain why
the differences.
3. List possible sources of error in your experimental setup.
4. Perform a percent difference calculation at both freezing and boiling between the
predicted and measured values. Were they the same or different? Explain.
5. Plot the predicted data points for -100. oC and 200.oC on your graph. Does your
error get greater or less? Explain.
Going Further:
1. Using the current atmospheric pressure of 30.9inHg and calculate the moles of
gas present using the ideal gas law.
2. Calculate the molar volume using the combined gas law adjusting to STP.
3. Use the adjusted volume to determine the molar density of the gas (g/cm3)