Demos: 3E-04 Mist & Fog


A large, thick-walled flask, containing a small amount of water, is pressurized by the lecture desk air supply. When the pressure is quickly reduced back to ambient pressure, a fog appears in the flask and water droplets can be seen on the flask walls due to condensation.

Directions: Open the stop cock and attach the air supply hose to the flask. Turn on the air supply. The pressure will build to approximately 40 psi. Close the stop cock and remove the supply hose. With a bright light shining on the flask, quickly open the stop cock. A fog should be visible. (If there is a way to introduce smoke particles into the flask just before attaching the hose, the fog will be more pronounced. See the lab tech for details about doing this.)

Suggestions for Presentation: Discuss weather situations in which the air is saturated and there is a pressure drop. Clouds begin to form. Show this in the demo. The water condensing on the sides of the glass is like dew forming.

Applications: Low pressure systems in the atmosphere produce clouds and/or rain.

Add to Cart | View Cart
Last Updated: May 9, 2016 11:44 AM