Science in Motion
Lab Time: 15 – 20 minutes, 30 – 40 minutes with extension
Grade Level: 8 – 12, physical science, chemistry, and physics
Objective: In this experiment, students will:


Study the relationship between the temperature of a gas sample and the pressure it exerts.
Determine from the data and graph, the mathematical relationship between the pressure and absolute temperature of a confined gas.
 Find a value for absolute zero on the Celsius temperature scale.
Major Concepts:
Students should have a basic understanding of the kinetic molecular theory and the motion of molecules in the gas phase. An understanding of temperature and absolute units are essential.
Students should know several of the common units used in pressure measurement such as atmospheres, Torr, mmHg and KPa. This lab can be easily incorporated as an inquiry based introduction, a core illustration lab or an end of the chapter review lab.
Preparations:
1. To save lab time, set up the computer, the interface and the probes.
2. The default calibration for this experiment has units of kPa (kilopascal). You can also select other pressure units (mm Hg or atm) when using Logger Pro program.
3. In order to save time, you may prefer to prepare hot water baths ahead of time. If 1-liter beakers are in short supply, students can share the ice water bath and room temperature baths.
For safety reasons, the hot and boiling water baths should not be shared.
4. Water baths do not have to be done in the order stated in the procedure, however, students
should NOT do the Boiling water consecutively with the Ice water bath.
5. The rubber stopper must fit tightly into the 125 mL flask. Leaks will cause errant pressure
readings.
Pressure vs. temperature (K) Absolute zero determination
Lab #802, Pressure-Temperature Relationship of Gases , (5/29/08) Advancing Science Program, Gettysburg College, Gettysburg, PA 17325, www.advancingscience.org
Science in Motion

Teacher Notes Science in Motion
Pressure
(kPa)
96.5
Temperature
(°C)
0.0
Temperature
(K)
273.0
Constant, K
(P / T)
0.354
102.3
110.7
19.9
44.2
292.9
317.2
0.349
0.349
130.8
Answers to Questions:
99.7 372.7 0.351
1. In order to perform this experiment, what two experimental factors were kept constant?
Volume of the gas and number of molecules were kept constant.
2. Based on the data and graph that you obtained for this experiment, express in words the relationship between gas pressure and temperature.
Pressure varies directly with the absolute temperature, if the volume and number of gas molecules are kept constant.
3. Explain this relationship using the concepts of molecular velocity and collisions of molecules.
An increase in temperature causes molecules to move at a higher velocity. Faster-moving molecules have more collisions with the walls of the container, resulting in a higher pressure.
4. Write an equation to express the relationship between pressure and temperature (K). Use the symbols P, T, and k.
P/T = k (or T/P = k)
5. One way to determine if a relationship is inverse or direct is to find a proportionality constant, k, from the data. If this relationship is direct, k = P/T. If it is inverse, k = P • T. Based on your answer to Question 4, choose one of these formulas and calculate k for the four ordered pairs in your data table (divide or multiply the P and T values). Show the answer in the fourth and fifth columns of the Data and Calculations table. How “constant” were your values?
P/T was a constant. The average value was 0.351 kPa / K (see values in the sample results).
6. According to this experiment, what should happen to the pressure of a gas if the Kelvin temperature is doubled? Check this assumption by finding the pressure at -73°C (200 K) and at 127°C (400 K) on your graph of pressure versus temperature. How do these two pressure values compare?
Pressure is expected to double if absolute temperature doubles. The pressure at 200 K is ~ 70
kPa and the pressure at 400 K is ~140 kPa. The second pressure is double that of the first.
Boyles Law: Pressure – Volume Relationship of Gase was adapted from (Lab #6) Chemistry with Computers , by Dan Holmquist and Donald
Volz. The lab was adapted by Jack Sipe for the Advancing Science Program at Gettysburg College, Gettysburg, PA 17325 http://www.advancingscience.org
2T
Lab #802, Pressure-Temperature Relationship of Gases , (5/29/08) Advancing Science Program, Gettysburg College, Gettysburg, PA 17325, www.advancingscience.org
Science in Motion