5.19 Superheated Steam

Chemical Concepts Demonstrated: Superheated steam, misconceptions about steam

Demonstration:

Boil the water inside the flask and heat the copper condensation coil. Hold a piece of filter paper or a long-stem match in the path of the steam.

Observations:

    The filter paper is charred where it touches the steam.  If a match is held in the steam, it ignites.

Explanation:

    Depending on what level class is being taught, the students might believe that steam is the fog that appears above boiling water.  To show that these clouds are recondensed water vapor, it should be noted that the superheated steam itself has no visibility to it.  This steam (due to the additional heat added to the copper coil) is well above the boiling point for water, and is hot enough to char filter paper and light matches.