Wikijunior:Big Book of Fun Science Experiments/Explosive foam

You really need a proper science lab and a trained presenter to do this experiment. It is more of a demonstration than a participatory exercise.

Ingredients

 * A tub which holds about 1 gallon
 * Water
 * Soap
 * A beaker or test tube
 * A stopper with a hole
 * Glass elbow and rubber tubing
 * Hydrochloric acid
 * Magnesium ribbon
 * A lighter

What to do

 * Step 1: Fill the tub with very soapy water
 * Step 2: Fill the beaker or test tube about half way with hydrochloric acid
 * Step 3: Attach the glass elbow and the hose to the stopper
 * Step 4: Place the other end of the hose in the tub of soapy water
 * Step 5: Add a small amount of the magnesium ribbon to the beaker and quickly cover the top with the stopper; hold the beaker so it is lower than the tub and there are no kinks in the hose
 * Step 6: Bubbles will appear in the tub
 * Step 7: Pick up some bubbles with your hand and light them with the lighter; they should go up quite spectacularly without burning your hand
 * Step 8: When you get tired of playing with the bubbles, you can light the ones left in the tub all at once. FWOOSH!

Principle
Magnesium and hydrochloric acid react to create hydrogen gas and magnesium chloride. The chemical equation looks like this:

Mg (s) + 2HCl (aq) --> H2 (g) + MgCl2 (aq)

Because Hydrogen gas is lighter than air, it travels up the tube and bubbles through the water. Hydrogen gas burns at a relatively low temperature and shouldn't harm your hand when you light it.