If you had a high-speed camera that could capture a photograph of the billions of billions of speeding molecules in a cubic centimeter of air, there would not be much to see. The actual air molecules take up only one tenth of one percent of the space they occupy. At room temperature, most of that cubic centimeter of air, 99.9%, is actually vacuum. Heat up that one cubic centimeter of air and the percent that is vacuum would increase.

Today students observe the effects of heating and cooling 1,000 cubic centimeters of air. They make annotated drawings that explain these effects in terms of heating and cooling air at the particle level. They complete the list of properties of air they began in Investigation 13.

By the end of this session students will understand that air expands when it is warmed and contracts when it is cooled and these phenomena can be explained in terms of the motion of particles.

Learning Goals

• Understand that air expands when it is warmed and contracts when it is cooled and these phenomena can be explained in terms of the particles that make up gases
• Understand the connection between change in temperature and change in particle speed

Sequence of experiences
1. Ask the question	All Class	5 Mins
2. Use the Particle Magnifier	All Class	5 Mins
3. Make annotated drawings	All Class	10 Mins
4. Discuss annotated drawings	All Class	15 Mins
5. Add properties	All Class	10 Mins

Materials and Preparation

For the class:

• Post the investigation question in a place where all students can see it.
• Properties of Air chart (from Investigations 14 and 15)
• Annotated Drawing Poster (See Resource Quick Links, also used in Investigation 6)
• The Particle Magnifier (Water-Air), using a classroom computer and projector or Smart Board
  [Launch Particle Magnifer (Water-Air) in a new window]
• Bubble mix (prepared earlier)
• 1 12oz plastic cup
• 1 1-liter plastic bottle
• 2 1gal buckets 1/2 filled with hot and cold water