Superheated Steam

Making fire with steam

We usually think of water as a substance used to put out fires… but what happens when water turns to steam and that steam gets superheated? Watch in amazement as the steam produced in the experiment is used to create – not extinguish – fire!

Experiment Materials

  • Bunsen burner or hot plate
  • Copper tubing
  • 500 mL flask
  • Water
  • One-hole rubber stopper
  • 2 blow torches
  • Matches
  • Tongs
  • Piece of black paper

Experiment

Making the Copper Coil

  1. Create a coil in the copper tubing about 8 cm (3 in) in diameter with approximately 8 cm of tubing left on either end of the coil.
  2. Create a right-angle in one end of the tubing and a small crimp in the other end – being careful to not completely close off any part of the tubing.
  3. Gently blow into one end of the tubing to make sure that the air is free-flowing. Important: If any part of the tubing is closed off an explosion can occur from the steam building up.
  4. If air flows freely through the tubing, insert the end with the bend into the hole in the rubber stopper.

Superheated Steam

  1. Pour 200 mL of water into the flask and put in the rubber stopper.
  2. Place the flask on the burner or hot plate and turn on the heat.
  3. Let the water boil until steam begins to form. You can see if steam is coming out of the copper tubing by putting a piece of black paper near the end of the copper tubing.
  4. Once steam begins coming out of the tubing, hold one blow torch above the tubing and have an assistant hold the other blow torch under the tubing until it reaches about 400 degrees Celsius (752 degrees Fahrenheit). The steam should no longer be visible at this temperature.
  5. Using the tongs, hold the match in front of the tubing.
  6. Instantly, the match will ignite!
  7. You can also use the tongs to put a piece of paper in front of the tubing and watch it scorch in the heat.

How Does It Work?

The boiling point of water is 100 degrees Celsius (212 degrees Fahrenheit).  When water reaches this temperature it starts to change from a liquid to a gas, creating steam. In order for water to change from liquid to vapor the molecules need energy.  For one gram of water it takes 540 calories of heat energy to convert the water to steam.  This conversion process is called the Heat of Vaporization.  During the Heat of Vaporization, water can exist in both a liquid and gas state because the temperature does not increase, just the amount of energy increases. The steam would have much more heat energy than the water because of the calories of energy it has absorbed. 

When the copper tubing is heated with the blow torch, the temperature of the steam increases greatly and energy is absorbed by the steam in the tubing.  However, the water in the flask stays at a constant 100 degrees Celsius.  Since the steam is superheated when it exits the copper tubing, it can easily light the match on fire.