chemistry homework’s
Chem 104
NAME_________________________
Homework #9
Due Monday 14 November 2022
The PhET Simulation “Gases Intro” will be used to explore gas laws.
Go to the following site: https://phet.colorado.edu/en/simulation/gases-intro and answer the questions.
Size vs Speed of Particles
1. Click on the Intro icon. Click the green + sign to open the Particle box. Pump 100 heavy, blue
gas molecules into the chamber. Explain their behavior. Do they move fast or slow? Do they
curve or move in straight paths? What happens when they touch other gas molecules?
2. Now click the red dot under the pump that represents the smaller gas particles. Pump in 100
light, red gas molecules into the chamber. Explain how their behavior is similar or different to
the heavy particles.
3. What is the relationship between the size of the particles and the speed of the particles?
4. What type of relationship is this: directly proportional or inversely proportional?
5. Sketch a graph that represents this relationship:
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Chem 104 – Gas Laws
Temperature (T) vs Pressure (P) of Particles
1. Click the heat control handle on the bucket below the gas chamber. Drag it upward to increase
the heat to 500 K (227 °C). What is the current pressure?
2. Now increase the heat to 1000 K (727 °C). What is the pressure at this temperature?
3. What is the relationship between pressure and temperature?
4. What type of relationship is this: directly proportional or inversely proportional?
5. Sketch a graph that represents this relationship:
Volume (V) vs Pressure (P) of Particles
1. Reset the system by clicking the orange circle with the curved arrow in the far right corner.
2. Click on the collision counter to open the Wall Collision window. Set Sample Period to 20 ps.
3. Click the green + sign to open the Particle box. Pump 100 heavy blue gas molecules into the
chamber, and then pump in 100 light red molecules. Allow the molecules to spread out equally
for 20 – 30 seconds.
4. Click the green GO arrow in the collision counter box to measure the number of collisions in 20
ps. Next click the green GO arrow a few more times. Notice how the number of collision
changes each time.
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Chem 104 – Gas Laws
5. Now select the Width ↔ check box at the top right. A dashed line with arrows will appear below
the chamber indicating the current width is 10.0 nm. Record the maximum chamber width, speed
of the particles, and current temperature and pressure below:
Chamber Width: ___________
Pressure: _____________
Temperature: _____________
Average Wall Collisions: ___________
6. Click on the gas chamber’s left side handle and drag the chamber wall to the left as far as it will
go. Record the maximum chamber width, speed of the particles, and current temperature and
pressure below:
Chamber Width: ___________
Pressure: _____________
Temperature: _____________
Average Wall Collisions: ___________
7. Click on the gas chamber’s left side handle and drag the chamber wall to the right as far as it
will go. Record the maximum chamber width, speed of the particles, and current temperature
and pressure below:
Chamber Width: ___________
Pressure: _____________
Temperature: _____________
Average Wall Collisions: ___________
8. What is the relationship between the number of wall collisions and the pressure?
9. What type of relationship is this: directly proportional or inversely proportional?
10. Sketch a graph that represents this relationship:
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Chem 104 – Gas Laws
11. What is the relationship between the volume of the chamber and the pressure?
12. What type of relationship is this: directly proportional or inversely proportional?
13. Sketch a graph that represents this relationship:
Temperature (T) vs Volume (V)
1. Click the LAWS icon at the bottom menu to switch tabs.
2. Click the green + sign to open the Particle box. Pump 100 heavy, blue gas molecules into the
chamber, and then pump in 100 light, red molecules. Allow the molecules to spread out equally
for 20 – 30 seconds.
3. In the HOLD CONSTANT menu, select Pressure
V. Now select the Width ↔ check box at
the top right. A dashed line with arrows will appear below the chamber indicating the current
width is 10.0 nm. Record the current chamber width, temperature and pressure below:
Chamber Width: ____________
Pressure: ____________
Temperature: ____________
4. Click the HEAT control handle on the bucket below the gas chamber. Adjust the temperature to
400 K (127 °C).
Record the current chamber width, temperature and pressure below:
Chamber Width: ____________
Pressure: ____________
Temperature: ____________
5. What happens when you try to increase the temperature to 500 K (227°C)?
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Chem 104 – Gas Laws
6. What is the relationship between the temperature and volume, when pressure is held constant?
7. What type of relationship is this: directly proportional or inversely proportional?
8. Sketch a graph that represents this relationship:
Number of Particles (n) vs Temperature (T)
1. Reset the system by clicking the orange circle with the curved arrow in the far right corner.
2. Click the green + sign to open the Particle box. Pump 100 heavy, blue gas molecules into the
chamber, and then pump in 100 light, red molecules. Allow the molecules to spread out equally
for 20 – 30 seconds.
3. In the HOLD CONSTANT menu, select Pressure
T. Now select the Width ↔ check box at
the top right. A dashed line with arrows will appear below the chamber indicating the current
width is 10.0 nm. Record the current total number of particles, chamber width, temperature, and
pressure below:
Total Number of Particles: __________
Temperature: __________
Chamber Width: __________
Pressure: __________
4. Now increase the number of particles to 1000 so that there are 500 heavy, blue particles and 500
light, red particles. Record the current total number of particles, chamber width, temperature, and
pressure below:
Total Number of Particles: __________
Temperature: __________
Chamber Width: __________
Pressure: __________
5. What is the relationship between the number of particles and temperature, when the pressure and
volume are held constant?
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Chem 104 – Gas Laws
6. What type of relationship is this: directly proportional or inversely proportional? _
7.
8. Sketch a graph that represents this relationship:
Number of Particles (n) vs Volume (V)
1. Reset the system by clicking the orange circle with the curved arrow in the far right corner.
2. Click the green + sign to open the Particle box. Pump 100 heavy, blue gas molecules into the
chamber, and then pump in 100 light, red molecules. Allow the molecules to spread out equally
for 20 – 30 seconds.
3. In the HOLD CONSTANT menu, select Pressure
T. Now select the Width ↔ check box at
the top right. A dashed line with arrows will appear below the chamber indicating the current
width is 10.0 nm. Record the current total number of particles, chamber width, temperature, and
pressure below:
Total Number of Particles: _________
Temperature: _________
Chamber Width: _________
Pressure: _________
4. Now add 50 more blue particles and 50 more red particles so that the total particle count is 300.
Click on the gas chamber’s left side handle and drag the chamber wall to the left until the
temperature matches the initial temperature reading from Question #3 above. Record the
current total number of particles, chamber width, temperature, and pressure below:
Total Number of Particles: _________
Temperature: _________
Chamber Width: _________
Pressure: _________
9. What is the relationship between the number of particles and volume of the chamber, when the
temperature and pressure are held constant?
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Chem 104 – Gas Laws
10. What type of relationship is this: directly proportional or inversely proportional? _
11. Sketch a graph that represents this relationship:
Ideal Gas Law
The ideal gas law combines the variables for Pressure (P), Volume (V), number of particles (n), and
Temperature (T) into one equation. Based on the data recorded in this activity, try to write an equation
for the ideal gas law. The gas law constant has already been added for your convenience. (Hint:
Variables on the same side of the equation are inversely proportional, and variables on opposite sides of
the equation are directly proportional.)
___ ___ = ___ R ___
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Chem 104 – Gas Laws
