Cooling by expansion: Jar with water compressed with air.

Cooling by expansion: Fog made in jar with water and released compressed air. About 1 inch of water is placed in the bottom of the bottle, and a gas flame is introduced into the neck to supply ions. A rubber stopper is placed firmly onto the bottle. Compressed air is introduced into the bottle. The stopper is quickly removed. The sudden pressure drop causes heavy fog to condense. Ions from a bunsen burner are introduced into a large thick-walled glass bottle with an inch of water at the bottom. Compressed air is forced into the bottle through a stopper fitted with an air hose. A quick release of pressure will cause a drop of temperature in the bottle. This cooling causes fog drops to form around the ions and produce a dense cloud in the bottle. BOYLE'S LAW.