Summary

In this activity, students will use a simulation to view both macroscopic and particle-level animations modeling real-world scenarios to demonstrate the relationships between volume, temperature, and pressure of a gas sample. For each set of animations, they will answer a series of questions to develop the particle-level reasoning for the qualitative relationships.

Grade Level

High School

NGSS Alignment

This activity will help prepare your students to meet the following scientific and engineering practices:

• Scientific and Engineering Practices:
  • Developing and Using Models
  • Analyzing and Interpreting Data
  • Engaging in Argument from Evidence

Objectives

By the end of this activity, students should be able to:

• Describe the relationships between volume, temperature, and pressure in a gas sample based on particle movement.
• Apply their understanding of gas laws to predict or explain how gases behave in real-world scenarios.

Chemistry Topics

This activity supports students’ understanding of:

• Gas laws
• Volume
• Temperature
• Pressure

Time

Teacher Preparation: minimal

Lesson: 30-40 minutes

Materials

• Computer, tablet, or phone with internet access
• Student handout
• https://teachchemistry.org/classroom-resources/the-behavior-of-gases

Safety

• No specific safety precautions need to be observed for this activity.

Teacher Notes

• The simulation can be found at the following link (note that students can access the simulation without an AACT login):
  • https://teachchemistry.org/classroom-resources/the-behavior-of-gases
• This simulation could be used as a first introduction to the gas laws, or as a review after they have been covered. It focuses on the general principles of each relationship (pressure-temperature, volume-temperature, and pressure-volume) and how changes in the movement of gas particles cause changes in the macroscopic measurements.
• Students are first introduced to the concepts of volume, temperature, and pressure as they relate to a closed sample of gas.
  • Note that the gas samples discussed in this simulation are not reacting chemically and the number of gas particles in a sealed container remains constant. Gases in this simulation are treated as ideal gases.
  • While this simulation does not explicitly discuss kinetic molecular theory, it could be used as an introduction to the topic. Throughout the explanations in this simulation, definitions of volume, temperature, and pressure as related to gases are referenced and could be tied back to some of the key assumptions of kinetic molecular theory, including:
    • Gases are very far apart from one another compared to their size. Gases are compressible (their volume can change) because of the amount of space between particles.
    • The average kinetic energy of gas particles is dependent on the temperature. On average, the particles move slower at lower temperatures and faster at higher temperatures.
    • Collisions between gas particles and between particles and the container walls are elastic and no kinetic energy is lost. Pressure is a result of the force of particles colliding with the walls of their container.
• The photos used in the introduction are representative of the effect of different temperatures on a gas sample: for a rigid container (the aerosol can), volume won’t change, and for a flexible container (the balloon), volume increases as temperature increases (from a cold winter scene to a warm spring scene to a hot desert scene). Pressure could be different as well. These photos are not meant to illustrate any particular set of conditions, merely that different conditions will affect the properties of gases in different ways.
• In the “Pressure” section of the introductory screen, it says “Particles in a rigid container can generally be considered unaffected by outside pressure conditions.” This is true to a point – however, if the pressure difference between the inside and outside pressures becomes greater than what the container material can withstand, it will eventually implode (if outside pressure > inside pressure) or explode (if inside pressure > outside pressure, as is the case with the aerosol can in scenario 1 of this simulation).
• This simulation addresses gas laws in general terms through the lens of real-life scenarios.
  • Scenario 1: An aerosol can gets hot (ex: left in a car in the summer, left close to a heat source) and eventually explodes/fails because the pressure increases as it gets hotter, showing the relationship between pressure and temperature.
  • Scenario 2: A balloon moves from a warm environment (ex: indoors) to a cold environment (ex: outside in winter, a freezer) and gets smaller, showing the relationship between volume and temperature.
  • Scenario 3: A balloon is placed in a bell jar attached to a vacuum pump, which removes air particles/decreases the pressure inside the bell jar and increases the volume of the balloon, showing the relationship between pressure and volume.
    • While Scenarios 2 and 3 could be replicated in real life for a classroom demonstration, Scenario 1 (heating an aerosol can) is very dangerous and should not be attempted. Students could be directed to news articles about the dangers of aerosol cans being left in hot cars or near heat sources for further discussion.
• Specific values for temperature, pressure, and volume are not given in the animations, as the focus of this simulation is a general understanding of the relationship between these variables.
  • Use AACT’s The Gas Laws Simulation for a more in-depth mathematical exploration of Boyle’s Law (pressure and volume), Charles’ Law (volume and temperature), and Gay-Lussac’s Law (pressure and temperature).
• For each scenario, assume the variable that is not explicitly changing is constant:
  • Scenario 1: volume is constant, temperature and pressure change
  • Scenario 2: pressure is constant, volume and temperature change
  • Scenario 3: temperature is constant, pressure and volume change
• Each scenario contains a macroscopic animation and question set followed by a particle-level animation and question set. The macroscopic questions focus only on readily observable properties (volume, mass, and temperature) while the particle-level questions also include questions about how the particles are moving and colliding. This should help students draw the connection between observable properties and particle behavior that cannot be seen directly.
  • Note that the macroscopic questions ask students to think about the volume, mass, and temperature of the particles but not pressure. In a real-life scenario, students would be able to conclude that the mass is not changing because the sample is in a sealed container, and changes (or lack thereof) in temperature and volume (container size) would be felt or seen easily. Pressure is not as obvious and is understood better at a particle level, which is why pressure is introduced only in the questions about the particle-level animations.
  • Encourage students to watch the particle-level animations carefully, and to rewatch them as many times as needed. It may not be obvious to them at first how the particle movement is changing.
  • Note that students will need to answer each set of questions correctly before they can move on to the next section of the simulation.
• The extension questions ask students to relate what they learned about gas particle behavior to the mathematical definition of pressure, . This is a great way to connect to math and physics concepts. Mathematical connections could also be made to density – anything that causes a change in volume would also change the density of a gas sample.
• Other gas simulations for further exploration:
  • The Concord Consortium:
    • Gas Laws simulation suite
    • Gas Laws and Weather Balloons activity module
  • PhET:
    • Gases Intro
    • Gas Properties
• Related classroom resources from the AACT Library that may be used to further teach this topic:
  • Simulation: The Gas Laws Simulation
  • Animation: Gases
  • Unit Plan: The Gas Laws
  • Activity: Understanding Gas Laws
  • Lab: Investigating the Power of Air Pressure
  • Demonstration: Inflate and Shrink Wrap a Student
  • Lab: Three Station Gas Lab
  • Lab: Exploring Gases