Adapted from: Meridian Creative Group, a Division of
Larson Texts, Inc. (1996). CBL Explorations in Chemistry for the
TI-82 and TI-83
- University of Virginia
- Physics Department
Determining Absolute Zero
A Physical Science Activity
2003 Virginia SOLs
For instructions on how to download the CBL programs necessary for this activity,
- use Calculator-Based Laboratory (CBL) equipment to measure temperatures
and pressures of gas samples;
- graph pressure vs. temperature plots;
- extrapolate graphs to determine the value of absolute zero.
- Is there a limit to how cold something can get? What would
make an object stop getting colder? What is this limit, and how
can we find it?
Temperature is a measure of the kinetic energy (or movement) of
particles inside of an object. If particles have a lot of kinetic
energy, the object will have a high temperature, and if particles
have less kinetic energy, the object will have a low temperature. So,
the lowest temperature an object can have happens when the particles
in the object are not moving at all. We call this temperature
absolute zero. This is zero Kelvin (the SI unit for
temperature), and -273 C° on the Celsius scale. When particles
in a gas stop moving and are at this point of absolute zero, the
pressure of that gas is also zero. If particles are not moving, they
are not bouncing around and hitting their container, so there is no
pressure being exerted. In this activity, students will measure
pressures and temperatures of gas samples, make a graph, and then
extrapolate the data to determine the temperature at zero pressure.
This should give them the temperature at absolute zero.
To print out the Student Copy only,
- TI-83 Graphing Calculator
- Link Cable
- CHEM-BIO program from Vernier loaded on the calculator
- Vernier Pressure Sensor with syringe and CBL DIN adapter
- Temperature Probe
- 2 rubber bands or tape
- Hot plate
- 4 beakers to be filled with water of different temperatures
- boiling water
- warm water
- room temperature/cool water
- ice water
- Graph paper
- Place 2 beakers of water on hot plate. Leave one on long
enough to get warm water and leave the other on long enough to
- Fill a third beaker with room temperature/cool water and a
fourth with cool water and ice.
- While water is warming up, set up the CBL, calculator, and
other equipment as in the following figure.
- Connect the CBL and TI-83 calculator with the black link cable. Use the
piece of tubing to connect the syringe to the pressure sensor and the CBL
DIN adapter to connect the pressure sensor to the CBL. Open the blue valve
on the pressure sensor to open the syringe to the outside air. Fill the syringe
to 10cc of air and then turn the blue valve to close off the syringe to the
outside air. Connect the pressure sensor to channel 2 (CH2). Connect the temperature
probe to channel 1 (CH1) on the CBL. Attach the temperature probe to the syringe
using the rubber bands or tape so that they will stay together when you are
- Once all of your equipment is connected, and the water baths
have reached appropriate temperatures, begin the data collection
- Turn on the TI-83 calculator and the CBL. Press the PRGM
button on the calculator to get a listing of your programs. Move
your cursor or press the correct number to select the CHEMBIO
program. Press ENTER again to start program. Follow the directions
on the screen until you reach the main menu for the program.
- Choose SET UP PROBES from the list. The CBL screen should have
three dashes across it (to signify communication between it and
the calculator) and the calculator should then give you a prompt
for the number of probes being used. In this case we are using the
pressure and temperature probes, so we will press 2 and ENTER.
- Next you will need to select the correct probes and channel
numbers. Remember the temperature probe is in CH1 and the pressure
probe is in CH2.
- The stored calibration for the pressure sensor should work. If you are getting
reasonable data, use it and ATM for the units. If you are getting bad data,
you may need to calibrate the pressure sensor. Select the manual entry option.
For atmospheres, the intercept is 0.729 and the slope is 0.271. If you wish
to use a different unit, you can find the calibration numbers on the Vernier
- You should now be back at the main menu for the program. Now
we want to choose COLLECT DATA and then choose MONITOR INPUT. At
this point, both the CBL and calculator should be showing readings
from the probes.
- Now we want to place the syringe and temperature probe into
the first temperature bath. Start with the ice water because it is
easier to warm up the temperature probe than it is to cool it
down. Make sure you do not get the pressure probe itself wet. Just
put the syringe into the water.
- Watch the readings on the calculator. Once they stabilize,
record readings of temperature (in Celsius) and pressure in data
- After these numbers have been recorded, move the syringe to
the room temperature/cool water bath. Again, wait for the readings
to stabilize and record them in the data table. Repeat these steps
for the warm water and boiling water baths.
- Once you have done all four baths, press the + button on the
calculator to stop the readings. Disassemble and clean up all of
- Convert temperature readings to Kelvin and record those in the
- Make a graph of pressure (Y-axis) vs. Kelvin temperature (X-axis), start
- Draw a line to best fit the shape of the graph. Continue this
line so that it passes through a pressure reading of zero (crosses
the x-axis). Read this temperature and record this as the value
for absolute zero.
To print out the Data Sheet only,
Temperature (°C) CH1
Pressure (atm) CH2
Room Temp/Cool Water
Absolute zero = ______________K
- Have students run the program on the calculator so that the points will
be plotted for them. Take them through the steps to find a best fit line and
have the calculator draw the line for them. They can then trace this line
to find where absolute zero occurs.
- Have students repeat the activity with a different gas. Some
suggestions are helium (used to fill up balloons) or carbon
dioxide from dry ice. The slopes of the lines should be different,
but they should all converge at absolute zero.
Students with Special Needs
All students should be able to participate in this activity.
Click here for further
information on laboratories with students with special needs.
- Walk around and check the students' graphs to make sure they
are doing them correctly.
- Have students write a conclusion to the experiment. They
should explain what absolute zero is and how they went about
determining the value of it. They should also explain what the
graph shows. What sort of relationship is there between pressure
and temperature? What is the lowest possible temperature we could
ever reach? What are some sources of error in the experiment? If
they had to do the experiment over, what are some changes they
could make for it to be more accurate?