Summary

In this simulation, students will investigate three of the fundamental gas laws, including Boyle’s Law, Charles’ Law and Gay-Lussac’s Law. Students will have the opportunity to visually examine the effect of changing the associated variables of pressure, volume, or temperature in each situation. Also, students will analyze the gas samples at the particle level as well as manipulate quantitative data in each scenario. Finally students will interpret trends in the data by examining the graph associated with each of the gas laws. This lesson accompanies the simulation from the November 2015 issue of Chemistry Solutions.

Grade Level

High or middle school

Objectives

By the end of this lesson, students should be able to

• Understand that pressure and volume have an indirect relationship, when temperature is held constant, as shown with Boyle’s Law.
• Understand that temperature and volume have a direct relationship, when pressure is held constant, as shown with Charles’ Law.
• Understand that pressure and temperature have a direct relationship, when volume is held constant, as shown with Gay-Lussac’s Law.
• Accurately calculate the final values for volume, pressure or temperature of a gas sample based on a set of given conditions.
• Predict the spatial distribution of particles in the gas sample as variables are changed.
• Describe the interaction and motion of particles in the gas sample as variables are changed.
• Interpret trends in the data by examining the graph associated with each of the gas laws. 

Chemistry Topics

This lesson supports students’ understanding of

• Gas Laws
• Volume
• Temperature
• Pressure

Time

Teacher Preparation: 10 minutes

Lesson: 45–60 minutes

Materials

• Computer with internet access
• Calculator
• teachchemistry.org/gaslaws

Safety

No specific safety considerations are needed for this investigation.

Teacher Notes

• This simulation is designed so that students can interact with Boyle’s Law, Charles’ Law and Gay-Lussac’s Law separately. Tabs on the top on the screen will allow for selection of the particular law to investigate.
• This simulation is intended for students to practice completing the gas law calculations, as well as to connect specific particle behavior with the associated variable of volume, temperature or pressure.
• In addition, by clicking on the “Add Data” button, students can collect data to create a graph for each of the gas laws.
• Depending on the gas law chosen, the variable that is held constant will not be available to manipulate at any point on that particular screen.
• The arrows that appear near each variable should be clicked on to either increase or decrease the particular variable. The exact values will be displayed at the bottom of the screen in the variable list.
• Note that the Celsius temperature value can be shown on the thermometer, but the kelvin value is used for the calculations. When the Kelvin temperature exceeds 423K, the Celsius thermometer will appear to break, as it exceeds its capacity.

Answers to the student activity

Pre-lab Questions:

1. a. = 4.16
1. b. = 3.52
1. c. = 636

2. a. Volume- References the amount of 3-dimensional space that is occupied by the gas particles. Common units include L, mL, cm³.

2. b. Pressure- Commonly described as force per area. Although it is often difficult for students to explain, gas particles exert a force on any surface, so in turn this is known as pressure.  Gas particles exert force during a collision with other particles, as well as with the surface of a container. The more often the particles of a gas collide (with one another or with a surface), the higher the gas pressure will be. Common units include: atm, kPa, mmHg, psi.

2. c. Temperature – this is a measurement of the kinetic energy (motion, speed) of the gas particles. The faster the particles are moving, the higher the temperature will be. Common units include: K, ⁰C, ⁰F (in order to solve a gas law equation the Kelvin temperature value must be used).  

Answers to the student activity:

Boyle’s Law Activity Questions:

1.  Temperature

2. a) Space between particles decreases; the number of collisions between particles increases as well as the number of collisions with the surface of the container.
2. b) P₂ = 1.76atm
2. c) n/a

3. a) Space between particles increases; the number of collisions between particles decreases as well as the number of collisions with the surface of the container.
3. b) V₂ = 4.29L
3. c) n/a

4. a) b) c) Answers shown in completed data table below:

4. d) Volume will decrease.
4. e) Indirect relationship (student justification will vary)
4. f) The gas pressure inside the bottle will double. Since the variables in Boyle’s law are indirectly related, they will have opposite outcomes.

Charles’ Law Activity Questions:

1. Pressure

2. a) The particles should begin to move faster as the temperature increases, and the space between the particles should increase.

2. b) 4.46L

2. c) Direct relationship, as temperature was increased, the volume of the gas also increased.

3. a) As the volume is decreased the space between the particles decreases, and the speed of the particles decrease (because temperature is also decreasing). Since pressure remains constant the number of collisions between particles should not change.

3. b) T2=185K
3. c) n/a
3. d) -88⁰C

4. a) The graph should have a positive slope.

4. b) When the temperature of a gas increases, the volume will also increase, and vise-versa. When the temperature of a gas decreases, the volume will also decrease, and vise-versa.

5. The gas would need to expand its volume to twice its original amount, this may cause the sealed container to explode!

Gay-Lussac’s Law Activity Questions:

1. a) Charles’ Law.
1. b) Volume.
1. c) This means that Gay-Lussac’s law will also have a direct relationship between its variables.

2. a) b) c) Answers shown in completed data table below:

2. d) As the pressure of the gas is increased, the temperature of the gas also increases. This is a direct relationship between the variables.

3. a) The speed of the particles will decrease, and the number of collisions between the particles, as well as the number of collisions with the surface of the container will also decrease.
3. b) 0.530atm
3. c) n/a

4. The pressure would also decrease by half of its original value, as long as the volume remains constant.

Checking Comprehension Questions:

1. T₂ = 429 K

2. P₂ = 1.39atm (make sure to remind students to convert the temperature values to Kelvin before solving the problem).

3. V₂ = 2.70L