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Exploring the Simple Gas Laws

When studying ideal gases, there are four different parameters to consider: pressure (P), temperature

(T), volume (V), and moles (n). The simple gas laws are described as “simple” because they focus on

the relationship between two of the parameters. This is accomplished by keeping the other two

parameters constant (unchanging) throughout the experiment. You will explore the simple gas laws

using the online Gas Properties PhET from the University of Colorado, Boulder.

1. Follow the link above to open the “Gas Properties” Simulation.

2. Click the “Ideal” tab.

Part 1: The Relationship Between Pressure (P) and Temperature (T)

In this part of the lab, you will explore how gases behave when you change the temperature of a system.

3. Look at the different parts of the simulation. Notice the Pressure Gauge, the “Heat/Cool” Bucket, the

thermometer and the pump.

4. Click and drag the handle on the tire pump one time. What happened in the simulation when you did

this?

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5. Next you will use the simulation to collect data to explore the relationship between the pressure of a

gas and the temperature of a gas. Do not add more particles to the system while collecting pressure data.

The number of particles (n) is held constant in this part.

Record the current temperature and pressure, then use the “Heat/Cool” Bucket to increase the

temperature of the system by approximately 100K. It is difficult to increase the temperature by exactly

100K. (See the sample data set below.) Record the new pressure. (The pressure will “jump” around.

Pick a pressure value that is “in the middle” of the fluctuating values.)

6. Repeat until you have obtained 5 data points. An empty data table is provided on the top of page 2.

Temperature

(K) Pressure (atm)

300 5.8

415 8.2

541 10.4

684 13.4

788 15.3

Sample Data Set for Part 1

https://phet.colorado.edu/en/simulation/gas-properties

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Your Data Table for Part 1

Temperature (K) Pressure (atm)

7. Using Excel or a similar program, prepare a graph of the data. Since temperature is the independent

variable in this experiment, it should be plotted on the x-axis. The graph should include a title and axis

labels, with the appropriate units. Don’t forget to save your work.

8. Reset the simulation by clicking on the orange button in the lower right-hand corner of the screen.

Reset button

Part 2: The Relationship Between Pressure (P) and Volume (V)

Next you will use the simulation to explore the relationship between the pressure of a gas and the

volume of a gas.

9. Add one or two “pumps” of gas molecules to the system. After this point, do not add more gas

particles to the system. The number of particles is held constant during the Part 2 experiment.

10. Temperature is also held constant during this part of the experiment. In the “Hold Constant” menu

on the right hand side of the screen, select “Temperature (T)” as shown below.

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11. Below the “Hold Constant” menu, click on the “Width” option. A value of 10.0 nm will appear

below the gas tank.

12. You will need to calculate the volume of tank. Assume that this first tank is a perfect cube with a

length and height of 10.0 nm. The length and height of the tank will remain constant throughout Part 2.

Only the width of the tank will change. The first volume can be calculated as follows:

𝑉𝑜𝑙𝑢𝑚𝑒 = 𝑙𝑒𝑛𝑔𝑡ℎ ∙ 𝑤𝑖𝑑𝑡ℎ ∙ ℎ𝑒𝑖𝑔ℎ𝑡

𝑉𝑜𝑙𝑢𝑚𝑒 = 10.0 𝑛𝑚 ∙ 10.0 𝑛𝑚 ∙ 10.0 𝑛𝑚

𝑉𝑜𝑙𝑢𝑚𝑒 = 1000 𝑛𝑚3

13. In the data table below, record the pressure associated with a volume of 1000 nm3. (The pressure

will fluctuate slightly so just record a “middle” value.)

Data Table for Part 2

Volume (nm3) Pressure (atm)

1000

14. Use the handle to make the tank about half as big. What happened to the pressure of the gas when

you decreased the volume of the tank?

15. Calculate the new volume of the tank, as shown below. The length and height remain at 10.0 nm.

𝑉𝑜𝑙𝑢𝑚𝑒 = 𝑙𝑒𝑛𝑔𝑡ℎ ∙ 𝑤𝑖𝑑𝑡ℎ ∙ ℎ𝑒𝑖𝑔ℎ𝑡

𝑉𝑜𝑙𝑢𝑚𝑒 = 10.0 𝑛𝑚 ∙ 5.0 𝑛𝑚 ∙ 10.0 𝑛𝑚

𝑉𝑜𝑙𝑢𝑚𝑒 = 500 𝑛𝑚3

16. Once the pressure stabilizes, record both the new volume and new pressure in the data table.

17. Expand the tank to a width of 15.0 nm. Wait for the pressure to stabilize and calculate the new

volume of the tank. Record these values in the data table.

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18. Collect two more data points. Adjust the tank to a new width. Calculate the new volume and record

the data. Repeat.

19. Using Excel or a similar program, prepare a graph of the data. Since volume is the independent

variable in this experiment, it should be plotted on the x-axis. The graph should include a title and axis

labels, with the appropriate units. Don’t forget to save your work.

20. Reset the simulation by clicking on the orange button in the lower right-hand corner of the screen.

Part 3: The Relationship Between Temperature (T) and Volume (V)

Next you will use the simulation to explore the relationship between the temperature and volume of a gas.

21. Add one or two “pumps” of gas particles to the system. After this point, do not add more gas

particles to the system. The number of particles is held constant in Part 3 of the experiment.

22. Since pressure will be held constant select “Pressure ↕V” from the “Hold Constant menu.

23. Click on “Width.”

Parameters for Part 3

24. As in Part 2, assume that the length and height of the tank are also 10.0 nm. Only the width of the

tank changes throughout the experiment. Record the temperature, in K, associated with the 1000 nm3

tank in the data table on the top of page 5.

25. Use the “Heat/Cool” Bucket to decrease the temperature of the system by approximately 50K. It is

difficult to increase the temperature by exactly 50K. The decrease does not have to be exact. Use the

new width to calculate the volume at the lower temperature. Record the new temperature and volume

values in the data table.

26. Decrease the temperature again. If you decrease the temperature too much, a pop-up (shown below)

will appear. If this happens, reset the simulation,

and begin Part 3 again.

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Data Table for Part 3

Temperature (K) Volume (nm3)

1000

27. Use the width to calculate the new volume at the lower temperature. Update the data table.

28. Now use the “Heat/Cool” bucket to increase the temperature to approximately 350K. Calculate the

new volume of the tank and record the data.

29. Collect one more data point at an even higher temperature. If a pop-up appears, reset the simulation

and begin Part 3 again.

30. Using Excel or a similar program, prepare a graph of the data. Since temperature is the independent

variable in this experiment, it should be plotted on the x-axis. The graph should include a title and axis

labels, with the appropriate units. Don’t forget to save your work.

31. Reset the simulation by clicking on the orange button in the lower right-hand corner of the screen.

Part 4: The Relationship Between Volume (V) and Moles (n)

In this part of the experiment, you will establish the relationship between volume and the number of gas

particles. The number of gas particles can be converted to moles by dividing by a constant, Avogadro’s

number. Since the only difference between the number of particles and moles is a constant, the

relationship between volume and the number of particles looks the same as the relationship between

volume and the number of moles.

32. Click on the “Width” option and reduce the width of the tank to 5.0 nm.

33. Click on the green plus symbol on the right-hand side of the screen. Use the single arrow to add 5

blue particles to the tank.

Click on the green button to open the

“Particles” menu.

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34. In the “Hold Constant” menu, select “Pressure ↕V” as pressure will be held constant throughout the

Part 4 experiment.

35. What is the temperature of the system? ____________________K

36. Calculate the volume of the tank. Assume that the length and width of the tank are both equal to

10.0 nm. Only the width of the tank will change.

Data Table for Part 4

Number of Particles Volume (nm3)

5 500

37. Add 1 or 2 more blue gas particles to the tank. Calculate the new volume and record this data in the

table above.

38. Keep on adding 1 or 2 blue gas particles to the tank. Record the number of particles and calculate

the new volume of the tank after each addition. Obtain 5 data points. It is important to note that in this

simulation you cannot exceed 15 total blue particles. In addition, you cannot reduce the number of

particles in the tank.

Add 5 “Heavy” particles to the tank

using the indicated button.

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39. What is the temperature of the system at this point? _____________________K Why is it

important to verify that the temperature did not change. (If it did, you will have to reset the simulation

and start Part 4 again.)

39. Using Excel or a similar program, prepare a graph of the data. Since the number of particles is the

independent variable in this experiment, it should be plotted on the x-axis. The graph should include a

title and axis labels, with the appropriate units. Don’t forget to save your work.

Questions

1. A direct relationship occurs when both variables move in the same direction. In other words, for a direct

relationship, as one variable increases, the other variable increases as well. An indirect relationship

occurs when the variables move in opposite directions. As one variable increases, the other variable will

decrease in an indirect relationship.

Complete this table. Use your notes, text, or the internet to research the name of each simple gas law.

The constants are the parameters (P,V, T or moles) that did not change over the course of the experiment.

Each part of the experiment had two variables (listed in the table) and two constants.

Relationship Direct or

indirect?

Constants Whose Law?

V vs P

V vs T

T vs P

Moles vs V

2. Using your results, explain each of the following scenarios. Make sure to refer to which graph (or simple

gas law) can be used as evidence for your answer.

a. Explain why bicycle tires seem flatter in the winter than in summer.

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b. Explain why a can of soda pop explodes if left in the hot sun.

c. A rigid container filled with a gas is placed in ice (ex. hydroflask). What will happen to the pressure

of the gas? What do you think will happen to the volume?

d. An infected tooth forms an abscess (area of infected tissue) that fills with gas. The abscess puts

pressure on the nerve of the tooth, causing a toothache. While waiting to see a dentist, the person

with the toothache tried to relieve the pain by treating the infected area with moist heat. Will this

treatment help? Why or why not?