How Do Variables Affect Pressure?
Introduction: In this activity you will investigate the relationship between volume, temperature, number of particles and pressure.
Go to http://phet.colorado.edu/en/simulation/gas-properties
Click “Run Now” or download the simulation
For the next 5 minutes become familiar with the simulation: Change various features, sliders, buttons, clickand-drag items, etc.
What are the two ways to add particles? How do you remove particles?
How do you release particles from the chamber?
How do you add heat?
How do you change volume?
While you are exploring, notice how the heat control affects the gas particles.
Next: Click “ Reset ” and conduct the following investigations.
Make sure the constant parameter is clicked on none .
Click the Heavy Species on the gas pump.
Set gravity to 0
Under Tools & Options , click on ruler and stopwatch
Your screen should look like the picture to right. This is considered “normal” conditions.
(Remember that any time you need to, you can use the on-screen
“Reset” button to return to the initial setup.)
Volume vs Pressure
How does changing volume affect pressure?
Volume
0 nm
2 nm
4 nm
6 nm
Pressure
Controlled Variables:
Amount of Gas: 50 aps
Constant parameter: temperature
Gravity: 0
Species: Heavy
Click and drag the scuba guy to the left as far as possible
Start the timer – stop at 20 p seconds
Record data – pressure and temperature
Repeat and move scuba guy 2 cm to the right each time
Number of Particles vs Pressure
How does changing the number of aps affect pressure?
Amount of Gas Pressure
250
350
450
550
Controlled Variables:
Volume: set as normal
Constant parameter: Temperature
Number of gps: 250 aps
Gravity: 0
Species: Heavy
Start timer – stop at 20 pseconds
Record data – pressure and temperature
Repeat by adding 100 more aps each time

Temperature and Pressure
How does changing temperature affect Pressure?
Temperature
400 K
600 K
800 K
1000 K
Pressure
Controlled Variable
Volume: normal
Number of particles: 100
Species: Heavy
Gravity: 0
Reset to normal conditions
Pump 100 particles into chamber
Add heat until temperature reaches ~400K
Start and run timer for ~20 p-seconds – record temp/pressure
Repeat, raising temperature by 200 K each time until 1000 K
Gravity
0
Gravity vs Pressure
How does changing gravity affect pressure?
½ way
Lots
Pressure
Controlled Variables
Volume: normal
Constant Parameter: temperature
Number of particles: 100 aps
Species: Heavy
Start with gravity at zero
Record temperature and pressure
Slide gravity to ½ across
Start and run timer for 20 pseconds, pause
Record temperature and pressure
Slide gravity to “lots”
Start and run timer for 10 pseconds, pause
Record temperature and pressure
1. Using the closest graph page in your science notebook, graph 3 of your data tables. Be sure to label the axis accurately and include the following titles:
Graph #1: Volume vs Pressure
Graph #2: Number of Particles vs Pressure
Graph #3: Temperature vs Pressure
2. Next to each graph, write a conclusion sentence. It should sound something like this: “
As _____________ increases, the pressure
_________________.”
3. Explain why bicycle tires seem more flat in the winter than in summer. Use evidence from your graphs to support your explanation.
4. Explain why a can of soda pop explodes if left in the hot sun. Use evidence from your graphs to support your explanation.
5. Describe: Under what specific condition will the lid be blown off the chamber? Is it possible to blow the lid with just one particle in the chamber?
6. Low-temperature physicists have not yet been able to cool anything to a temperature of absolute zero (0° K). a. Cool a simulated 50/50 sample (50 light and 50 heavy particles) gas sample to absolute zero. b. When the temperature hits absolute zero, are the particles shown to be at rest?
7. Use Scubie and the ice (“ Heat Control: Remove
”) to compress and cool a 50/50 sample to the smallest volume possible. Now use
Scubie to rapidly expand the volume of the chamber all the way out. a.
Describe what happens b.
Which species reaches the far side of the chamber where Scubie is first?