Zinc is a bluish-white metal used to galvanize iron, and is also found in alloys, batteries, and rubber. Sulfur is a yellow, brittle nonmetal; it can also be found in a powered form. Zinc and sulfur react with each other violently to produce zinc sulfide; the reaction is accompanied by a vigorous evolution of gas, heat, and light:
| Zn(s) + S(s) ——> ZnS(s) | [one of the easier chemical equations to balance!] |
The products of the reaction also include small amounts of zinc oxide (ZnO) and sulfur dioxide (SO2).
This reaction produces enough hot gas to propel small rockets; this was one of the model rocket propellants described by Homer Hickam in his book Rocket Boys (Delacorte Pr; 1998) [filmed as October Sky (Universal Studios, 1999)].
In the first demonstration below, powdered zinc and sulfur are mixed in a porcelain evaporating dish and heated with a flame; the mixture burns with a yellowish-green flame, and leaves a residue of yellow zinc sulfide in the dish. In the second video clip, a larger sample is ignited in an evaporating dish, which shatters; and in the third clip, a similar mixture cracks a large porcelain crucible.
Video Clip 1: REAL, 3.33 MB
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Video Clip 2: REAL, 1.41 MB
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Video Clip 3: REAL, 2.62 MB
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!!! Hazards !!!
This reaction produces a great deal of heat energy; clear the area of flammable materials.
This reaction must be performed in a fume hood or some open, well-ventilated area. If you do this in a fume hood, be prepared to spend some time wiping zinc sulfide powder off all of the surfaces in the hood.
Procedures
Bassam Z. Shakhashiri, Chemical Demonstrations: A Handbook for Teachers of Chemistry, Volume 1. Madison: The University of Wisconsin Press, 1983, p. 53-54.
References
John Emsley, The Elements, 3rd ed. Oxford, Clarendon Press, 1998, p. 120-121, 198-199.
David L. Heiserman, Exploring Chemical Elements and their Compounds. New York: TAB Books, 1992, p. 65-69, 122-124.
Martha Windholz (ed.), The Merck Index, 10th ed. Rahway: Merck & Co., Inc., 1983.
