Freezing Water By Pumping

Purpose

To freeze water by reducing the ambient pressure.
 

Equipment

Freezing by pumping chamber with cellophane watchglass, water and eyedropper, vacuum pump.

 

Suggestions

Ask your students whether this ice is cold like regular ice. Then pass the ice around for them to feel it.
 

Setup Time

5 min.
 

    Images

    i4-32

    Description

    Place about four drops of water onto a cellophane "watchglass" in the vacuum chamber and evacuate the chamber with the vcacuum pump. Almost immediately the water will begin to bubble (boil), and within about one minute the boiling will subside and the water will freeze. When the water freezes it is clearly seen to become opaque on the overhead projector screen, as seen in the photograph on the right above. 
     

    References

    Haym Kruglak and Paul M. Loofboro, Freezing Water by Evaporation, AJP 12, 48 (1944). Julius Sumner Miller, Freezing Water by Evaporation - A Remarkable Situation, AJP 18, 238 (1950). Z. V. Harvalik, Vacuum by Freezing, TPT 2, 178-179 (1964). R. L. Wild and D. C. McCollum, Dramatic Demonstration of Change of Phase, AJP 35, 540-541 (1967). Robert N. Stoller, Apparatus for Teaching Physics: Freezing-by-Boiling Apparatus That Does Not Require Acid, TPT 14, 59-60 (1976).