D R A F T
Gas Laws
The gas laws are defined by the relation PV = nRT. For a sealed container, the values of n and R are constants, so for any two states we can say that (P
1
V
1
)/T
1
=(P
2
V
2
)/T
2
. In this lab you will explore this relationship.
Purpose:
To verify the gas laws by holding each of the three parameters constant and then determining the relationship between the other two parameters
Equipment:
Pasco Heat Engine
Vernier Gas Pressure Sensor
Vernier Temperature Sensor
String with attached Mass Hanger
Slotted masses
Water containers (2)
Vernier Rotary Motion Sensor
Vernier LabPro Interface
Ring Stand i-Book computer
Ruler
Cautions:
This equipment is delicate. Everything should go together with the lightest of touches.
Do not force anything!
You may find that some of the setup procedure has already been done for you. Check each step to make sure that it is done properly. The success of your work depends upon correct setup!
Procedure to set up the heat engine
1.
Prepare two containers of water, one at room temperature and one with ice.
Rotary
Motion
Sensor
2.
Place the heat engine on the ring stand base.
3.
Attach the rotary motion sensor to the ring stand at the top of the rod, extending over the heat engine.
4.
Loosen the thumbscrew holding the heat engine piston, lift the piston to a point where the bottom of the piston is at the 50mm mark on the scale, and retighten the thumbscrew.
Tighten this screw lightly, just enough to hold the piston in position .
5.
Wrap the hook end of the string once clockwise around the middle pulley of the rotary motion sensor, hook the hook under the tray of the heat engine. There is a small hole
Hanging
Mass
(35g)
Pressure
Sensor
Ring
Stand
Mass
Platform
Hook
Heat
Engine
Aluminum Air
Chamber
TOPS_Thermo_Gas Laws 07_08.doc (Lyle, Adler) -- DRAFT Page 1

D R A F T in this tray to accept the end of the wire hook. Allow the mass holder to hang freely.
6.
The mass holder should be approximately 15cm below the pulley. You may lower the position of the rotary motion sensor on the ring stand a little to get close to the
15cm dimension.
7.
Adjust the heat engine so that the string from it to the pulley is vertical.
8.
Connect the tube from the aluminum air chamber to one port of the heat engine. Push and twist slightly to lock the tube in place.
9.
Connect the tube from the pressure sensor to the other port of the heat engine. Push and twist slightly to lock the tube in place.
10.
Connect the gas pressure sensor to the “CH 1” port of the LabPro interface.
11.
Connect the temperature sensor to the “CH 2” port of the LabPro interface.
12.
Connect the rotary motion sensor to the “DIG/SONIC “1 port of the LabPro interface.
13.
Connect the LabPro interface to the iBook computer with the USB cable. Either port will do.
14.
Plug the LabPro into a power outlet. After a short pause, it will beep merrily.
15.
Plug the i-Book computer in with its power adapter.
16.
Turn on the i-Book and wait for it to boot up.
17.
Log on to the computer with the username “student” and password “student”.
18.
Launch the “Ideal Gas Law” Activity by double-clicking it.
19.
A Sensor confirmation window will appear. Make sure that all three sensors have a green check mark, then click on OK to confirm.
Verification of temperature/pressure relationship at constant volume (Gay-Lussac’s
Law):
1.
Immerse the aluminum air chamber and the temperature sensor in the ice water bath.
2.
Wait one minute for the aluminum air chamber to cool down properly.
3.
Disconnect, then reconnect, one of the tubing connectors on the front of the heat engine apparatus. Turn the connector slightly counterclockwise and pull it out.
Reverse these steps to reconnect. This puts the entire apparatus at atmospheric pressure.
4.
Click on the zero button near the top of the screen on the iBook computer.
5.
Make sure the rotary motion sensor is selected and the gas pressure and temperature sensors are not.
6.
Click on OK to zero the rotary motion sensor.
Read steps 7-11 completely before performing them.
7.
Start the data collection process by clicking on the Collect button.
8.
Once data begins to show on the computer screen in the data table, move the aluminum air chamber and the temperature sensor from the ice water bath to the room temperature water bath.
9.
Wait until approximately 10 seconds have elapsed.
10.
Move the aluminum air chamber and the temperature sensor from the room temperature water bath to the ice water bath.
11.
The computer will automatically stop collecting data after 30 seconds, be sure that you have completed the procedure in that time.
TOPS_Thermo_Gas Laws 07_08.doc (Lyle, Adler) -- DRAFT Page 2

D R A F T
Recording your constant volume data
Copy the three curves on the display onto the axes below. Be as accurate as possible in reproducing the shapes of the curves:
P t
T t
V
Anal yzing your data
Looking at the graphs above, what is the relationship between pressure and temperature at constant volume? t
TOPS_Thermo_Gas Laws 07_08.doc (Lyle, Adler) -- DRAFT Page 3

D R A F T
Verification of temperature/volume relationship at constant pressure (Charles’
Law):
1.
Immerse the aluminum air chamber and the temperature sensor in the ice water bath.
2.
Wait one minute for the aluminum air chamber to cool down properly.
3.
Disconnect and reconnect one of the tubing connectors on the front of the heat engine apparatus. Turn the connector slightly counterclockwise and pull it out. Reverse these steps to reconnect. This puts the entire apparatus at atmospheric pressure.
4.
Loosen the thumbscrew on the heat engine. This frees the piston.
5.
Click on the zero button.
6.
Make sure the rotary motion sensor is selected and the gas pressure and temperature sensors are not.
7.
Click on OK to zero the rotary motion sensor.
Read steps 8-12 before performing them.
8.
Start the data collection process by clicking on the Collect button.
9.
Once data begins to show on the computer screen in the data table, move the aluminum air chamber and the temperature sensor from the ice water bath to the room temperature water bath.
10.
Wait until approximately 10 seconds have elapsed.
11.
Move the aluminum air chamber and the temperature sensor from the room temperature water bath to the ice water bath.
12.
The experiment will stop collecting data after 30 seconds, be sure that you have completed the procedure in that time.
TOPS_Thermo_Gas Laws 07_08.doc (Lyle, Adler) -- DRAFT Page 4

D R A F T
Recording your constant pressure data
Copy the three curves on the display onto the axes below. Be as accurate as possible in reproducing the shapes of the curves:
P t
T t
V
Anal yzing your data
Looking at the graphs above, what is the relationship between volume and temperature at constant pressure? t
TOPS_Thermo_Gas Laws 07_08.doc (Lyle, Adler) -- DRAFT Page 5

D R A F T
Verification of volume/pressure relationship at constant temperature (Boyle’s Law):
1.
Immerse the aluminum air chamber and the temperature sensor in the ice water bath.
2.
Wait one minute for the aluminum air chamber to cool down properly.
3.
Disconnect and then reconnect one of the tubing connectors on the front of the heat engine apparatus. Turn the connector slightly counterclockwise and pull it out.
Reverse these steps to reconnect. If the bottom of the piston is not at the 50mm mark, reset it while the connector is disconnected. Do not tighten the thumbscrew. This puts the entire apparatus at atmospheric pressure.
4.
Click on the zero button.
5.
Make sure the rotary motion sensor is selected and the gas pressure and temperature sensors are not.
6.
Click on OK to zero the rotary motion sensor.
7.
Start the data collection process by clicking on the Collect button.
8.
Once data begins to show on the computer screen in the data table, slowly push the platform down until the piston reaches the bottom of the cylinder, then slowly allow the piston to return to its original position.
9.
The experiment will stop collecting data after 30 seconds, be sure that you have completed the procedure in that time.
TOPS_Thermo_Gas Laws 07_08.doc (Lyle, Adler) -- DRAFT Page 6

D R A F T
Recording your constant temperature data
1.
Copy the three curves on the display onto the axes below. Be as accurate as possible in reproducing the shapes of the curves:
P t
T t
V
Anal yzing your data
Looking at the graphs above, what is the relationship between pressure and volume at constant temperature? t
TOPS_Thermo_Gas Laws 07_08.doc (Lyle, Adler) -- DRAFT Page 7

D R A F T
Introduction:
The gas laws can be condensed into a single equation: PV = nRT. For a fixed quantity of gas, this equation becomes (P
1
V
1
)/T
1
=(P
2
V
2
)/T
2
for changes between any two states.
All values must be in absolute form for this equation to work.
Experimental goals:
After completing this experiment, students will be able to:
1.
Describe the effect on pressure of varying temperature with volume held constant.
2.
Describe the effect on volume of varying temperature with pressure held constant.
3.
Describe the effect on pressure of varying volume with temperature held constant.
California Science Standards addressed in this laboratory activity:
Content:
2(b) Students know how to calculate changes in gravitational potential energy near Earth by using the formula (change in potential energy) =mgh (h is the change in the elevation).
3(a) Students know heat flow and work are two forms of energy transfer between systems.
Investigation & Experimentation:
1(a) Select and use appropriate tools and technology (such as computer-linked probes, spreadsheets, and graphing calculators) to perform tests, collect data, analyze relationships, and display data.
1(b) Identify and communicate sources of unavoidable experimental error.
1(c) Identify possible reasons for inconsistent results, such as sources of error or uncontrolled conditions.
1(d) Formulate explanations by using logic and evidence.
1(l) Analyze situations and solve problems that require combining and applying concepts from more than one area of science.
TOPS_Thermo_Gas Laws 07_08.doc (Lyle, Adler) -- DRAFT Page 8

D R A F T
Equipment:
Pasco Heat Engine
Vernier Gas Pressure Sensor
Vernier Temperature Sensor
Vernier Rotary Motion Sensor
Vernier LabPro Interface
Ring Stand
String with attached Mass Hanger
Slotted masses
Water containers (2) i-Book computer
Ruler
Key words : pressure, volume, temperature, Charles, Gay-Lussac, Boyle, gas, laws
Procedure notes:
Each lab group needs a minimum of 2 students
Students must complete the experiment in a timely fashion. Waiting too long for any part of the experiment will result in degraded results.
Answers to questions:
At constant volume, the temperature and pressure curves should be of the same general shape. Pressure is proportional to temperature,
At constant pressure, the temperature and volume curves should be of the same shape.
Volume is proportional to temperature.
At constant temperature, the pressure and volume curves should be mirror images of each other. Pressure is inversely proportional to volume.
References
Pasco equipment guide
Vernier probeware guide
California Science Standards
TOPS_Thermo_Gas Laws 07_08.doc (Lyle, Adler) -- DRAFT Page 9