Lab 2
The Ideal Gas Law and Heat Transfer
OBJECTIVES
1. Experimentally verify the Ideal Gas Law for air.
2. Determine Absolute Zero and the Universal Gas Constant.
3. Determine the fast way to cool a cup of hot water using heat transfer process of
conduction, convection, radiation and evaporation.
EQUIPMENT
DataStudio, absolute pressure sensor, temperature sensor, syringe, tubing, quickrelease coupling, metal canister with stopper, tubing-to-stopper connector
THEORY
Solid, liquid and gas are the most common states of matter found on this planet. The
only difference among all these states is the amount of movement of the particles that
make up the substance. The Ideal Gas Model allows one to make the following
statement: gases exert force on the walls of their containers by means of the continual
collisions of the gas molecules with the surface. The force per unit area is termed
pressure. Pressure depends on three parameters according to the kinetic-molecular
model of ideal gases: 1/Volume, temperature, and the number of moles.
From the ideal gas equation (pV = nRT), the absolute pressure is directly proportional to
the absolute temperature of the gas. If rewritten so as to plot the temperature vs.
pressure using the equation of a straight line, it reads T = (V/nR) p + 0K. The slope of
the line depends on the amount of gas in a container, but regardless of the amount of
gas, the intercept of the line with the temperature axis should be at absolute zero (or
273oC).
PROCEDURE
Part 1: Ideal Gas Law ― Pressure vs. Volume
a. Connect the syringe to the Capstone’s absolute pressure sensor using the tubing
and quick-release coupling. Set the initial syringe volume to 20.0 ml by disconnecting
the sensor from the coupling, moving the piston to the 20 ml mark, and reconnecting.
b. Measure the pressure at volumes of 20, 18, 16, 14, 12, and 10 mL. Use a pressure
vs. time graph to help identify constant pressure levels when making a
measurement.
c. Plot p vs. V and use Capstone’s curve-fitting tools to help determine whether your
data supports the ideal gas model. Interpret your plotted data and answer the
following questions:
 Interpret your plotted data and explain how the (i) pressure and volume behave
relative to each other and (ii) if temperature appears to be constant.
 Does the data agree with the Ideal Gas law?
d. Using this data, predicted the ratio (p2/p1)thy using the ideal gas law. Compare the
predicted (p2/p1)thy with the experimental value (p2/p1)expt using a percent difference.
How do they compare?
 Identify the sources of error in this experiment that may contribute significantly to
the percent error. How can you take the volume of the tubing into account? Does
this change the percent error?
 What happened to the pressure when the volume went from 20 mL to 10 mL?
Part 2: Ideal Gas Law ― Pressure vs. Temperature
a. Use a canister of air, a water bath and two sensors (absolute pressure and
temperature) to plot the pressure (kPa) vs. temperature (K) of air for different
temperatures in Capstone. Make sure that you have at least 10–15 data points that
span temperature ranges of about 20°C.
b. Apply a linear fit to your p-T data and determine the equation of the line.
c. From the slope of the fitted line, predict the Universal Gas Constant Rthy and
compare it with the accepted value of Raccepted = 8.31 J/mol∙K. How do they
compare? Hint: n/V = 42 mol/m3.
d. From the equation that fits your p-T data, calculate absolute zero, the temperature at
which the pressure goes to zero. Compare this to the accepted value Taccepted =
−273oC using a percent difference. How do they compare?
Part 3: What is the fastest method to cool a cup of hot water, if your only available
instrument is a spoon?
a. The only available equipment is a metal spoon, ice bath, breaker, Capstone
thermometer, and access to boiling water.
b. Design four different experiments and rank them in terms of which method of cooling
will be the slowest or fastest. Explain your reasoning!
c. To use the spoon, first dip the spoon into the ice bath and then into the hot water in
the breaker.
d. Do the experiments by measuring the temperature every 30 seconds for 8-10
minutes for each prediction. Plot all data on a single plot and interpret your results.