Calcium is a silvery-white metal; it is relatively soft, but much harder than sodium metal. Calcium is a member of the alkaline-earth metals (Group II on the periodic table); these metals react vigorously with water, although not as violently as the Group I metals such as sodium or potassium:
Ca(s) + 2H2O(l) ——> Ca(OH)2(aq) + H2(g)
In the following demonstration, a chunk of calcium metal is dropped into a beaker of distilled water. After a second or so, the calcium metal begins to bubble vigorously as it reacts with the water, producing hydrogen gas, and a cloudy white precipitate of calcium hydroxide. The presence of the hydroxide is demonstrated by the addition of a few drops of phenolphthalein indicator, which turns the solution pink, indicating that the solution is basic.
Video Clip: REAL, 4.31 MB
!!! Hazards !!!
Hydrogen gas is produced during the course of this reaction. If you are not collecting the gas, perform the procedure in a fume hood or a well-ventilated area to allow the gas to dissipate.
Producing Hydrogen Gas from Calcium Metal: Lee R. Summerlin, Christie L. Borgford, and Julie B. Ealy, Chemical Demonstrations: A Sourcebook for Teachers, Volume 2, 2nd ed. Washington, D.C.: American Chemical Society, 1988, p. 51-52.
John Emsley, The Elements, 3rd ed. Oxford, Clarendon Press, 1998, p. 48-49.
David L. Heiserman, Exploring Chemical Elements and their Compounds. New York: TAB Books, 1992, p. 84-87.
Martha Windholz (ed.), The Merck Index, 10th ed. Rahway: Merck & Co., Inc., 1983.