4. Air, a Gas:  Investigation 15

What are some properties of air? (2)

Plan Investigation 15

Particle Magnifier for Air and Water

At the macroscopic scale, air is common and familiar. At the particle scale, it remains such a mystery. In the seemingly still air of a room, countless particles (molecules) of nitrogen, oxygen, water vapor and other gases move faster than the speed of sound, constantly colliding with one another.

In today's investigation, students discuss two annotated drawings that explain the difference in compressibility between air and water. They use their experience with the Particle Magnifier to reason why water is not compressible. In discussion, they generate ideas about a particle explanation for the compressibility of air. This sets the stage using the Particle Magnifier to look at the particle model of air, a gas.

By the end of this investigation, students will understand that air is composed of particles too small and spread out to see. They will understand that because the particles are spread out, there is space for them to move closer together when air is compressed. Students will also know that air is a mixture of gases.

Learning Goals

  • Understand that air is made of particles too small and spread apart to see
  • Understand that air is a mixture of different gases, including water vapor
  • Understand that the relative compressibility of air and water can be explained in terms of the configuration of their particles
Sequence of experiences
1. Discuss annotated drawings Discussion 20 Mins
2. Show the Particle Magnifier All Class 15 Mins
3. Add to Properties of Air chart All Class 10 Mins

Materials and Preparation

For the class:

Prepare for use in Investigation 16:

  • Create bubble mix with the following ingredients. Mix these liquids, cover, and let sit for at least 12 hours prior to Investigation 16.
    • 80cc water
    • 40cc Joy dishwashing liquid
    • 10cc glycerin