Steam and Superheated Steam
Water is boiled and the steam is collected and run through a coil of copper tubing. The steam at this point is shown not to ignite a match or react significantly with steel wool. The equation for the slow reaction of steam with iron is given.
When a gas burner heats the steam coil strongly, the steam becomes superheated and is at a high enough temperature to ignite a match and react quickly with steel wool. The equation for the fast reaction of superheated steam with iron is given.
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Keywords
applications - practical/real-life, descriptive chemistry, enthalpy/heat, iron, kinetic-molecular theory, phase change, safety, water
Multimedia
Steam
Play movie
(QuickTime 3.0 Sorenson, duration 48 seconds, size 3.3 MB)
This demonstration illustrates the characteristics of steam under two different temperature conditions. Initially, water is simply boiled in a flask and allowed to pass through a coil of copper tubing. When a beaker is brought near the end of the tubing, the water condenses to liquid in the beaker. If a match is placed into the steam coming out of the copper tube, nothing happens. If a piece of steel wool is placed into the stream there is no observable change in the steel wool.
 Steam does not ignite the match. |
 Steam does not ignite the steel wool. |
Additional still images for this movie
Chart: Slow Reaction
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| 2Fe + 3H2O(g ) |
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Fe2O3 + 3H2(g ) |
Superheated Steam
Play movie
(QuickTime 3.0 Sorenson, duration 52 seconds, size 3.6 MB)
Two burners are ignited below the copper coil. These burners heat the steam to a very high temperature. The steam still condenses to liquid water in a beaker. A match placed into the superheated steam ignites. When steel wool is placed in the superheated steam, the steel wool glows brightly and reacts with the steam. Reaction with superheated steam can cause metal pipes in electric power plants to corrode and wear out.
(When very hot steam is used, the steam will react readily with iron and cause the tubes and other components of the power plant to form iron oxide. This places an upper limit on the temperature of the steam, which also limits the efficiency of the power plant.)
 Superheated steam ignites the match. |
 Superheated steam ignites the steel wool. |
Additional still images for this movie
Chart: Fast Reaction
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| 2Fe + 3H2O(g ) |
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Fe2O3 + 3H2(g ) |
Discussion
In an electric power generating plant, steam is used to turn turbines that generate electricity. The hotter the highest temperature of the steam is, the more efficient the plant is. When very hot steam is used, the steam will react readily with iron and cause the tubes and other components of the power plant to form iron oxide. This places an upper limit on the temperature of the steam, which also limits the efficiency of the power plant.
Demonstration Notes, Warnings, Safety Information, etc.
Exam and Quiz Questions
1. What happens to a match when placed into a stream of ordinary steam? What if the match is placed into superheated steam?
2. What is superheated steam? How can it be made?
3. What happens to steel wool that comes in contact with superheated steam? Name some problems that this could cause in an industrial setting.