So far in this unit, we have begun to establish basic relationships between gas variables, and we have also agreed on conventions to use for modeling gas particles. In this lesson, we will focus exclusively on gas particle behavior.

Kinetic molecular theory explains microscopic particle behavior based on the macroscopic properties of gases. The goal of this lesson is to understand how gas particles move, and how their microscopic movement is connected to the macroscopic observations of temperature and pressure.

You will explore gas particle motion using the simulation below.

• Select the "Ideal" option at left.
• Pump the pump once and observe the gas particles enter the box. Describe the movement of the particles below.
• Now choose an individual particle to focus on. Follow that particle's movements. Describe the movement of that single particle below.

Imagine you were the computer programmer that wrote the simulation. The programmer had to provide a set of rules for the movement of the gas particles that they obey in every possible circumstance within the simulation.

The simulation is again shown at right, click on "Ideal", then pump a single pump of gas and let the simulation run.

• Together with your lab table group, you will write out a set of rules that you believe gas particles are following in the simulation. Be as specific as possible and be prepared to share your rules with the class.

Now you will use your rules for particle movement  from page 2 (they are referenced on this page below) to help you program your own simulation using NetTango.

NetTango is a tool that uses a programming language called NetLogo in preprogrammed blocks. You will be asked to use these blocks to create a working model that best reflects the movement of gas particles you observed in the PhET simulation.

Watch the video that demonstrates how to use the blocks to program gas particle behavior at right.

Start programming!

A few quick points:

• Click  to reset the model and click  to run your model.
• Your code should always start with the  block, or the model will not know what to do.
• Your code will be performed by the particles continuously.
  • For example, if you wrote that "each particle + moves zig-zag", each particle in the model will move one step forward doing a zig-zag movement and then move one more step forward the same way, and so on. This will keep going on as long as the GO button is pressed.

Kinetic Molecular Theory is a set of rules used to describe gas particle movement. Scientists assume that all gas particles behave in this manner unless stated otherwise. These rules are as follows:

• Gas particles are in constant random motion.
• Gas particles are so small that they may be considered to have no volume relative to the empty space that surrounds them.
• Collisions with the walls of the container are perfectly elastic. An elastic collision is one in which there is no overall loss of kinetic energy. This means that gas particles do not lose kinetic energy after they collide with the walls of their container.
• Collisions between particles are also perfectly elastic. Kinetic energy may be transferred from one particle to another during an elastic collision, but there is no change in the total energy of the colliding particles.

You will model each of these rules in the questions below.

On the previous page, you were asked to model the rules of Kinetic Molecular Theory. Below are images showing how those models should appear. Your responses from the previous page are included here so you can compare and contrast them with the correct models.

Rule 1:

Rule 2:

Rule 3:

Rule 4: