Elephant's toothpaste

Elephant toothpaste

This experiment shows the decomposition of hydrogen peroxide catalyzed by Potassium Iodide. Hydrogen peroxide (H2O2) decomposes into water and oxygen gas, but normally the reaction is to slow to be easily perceived or measured: 2H₂O₂--->2H₂O_(l)+O_2(g)

odide ion from potassium iodide acts as a Catalyst– it speeds up the reaction without being consumed in the reaction process. The iodide ion changes the mechanism, by which the reaction occurs:
H₂O₂ + I^- ---> H₂O + IO^-
H₂O₂ + IO^- ---> H₂O + O₂ + I^-
________________________________
2H₂O₂ ---> 2H₂O_(l) + O_2(g) ΔrH°=-196 kJ/mol

Oxygen quickly leaves the system causing strong foaming of the detergent, so the foam erupts out. Steam rising from the foam shows that the reaction is exothermic (gives off heat). Minimum quantities of iodine are being liberated and can be detected by its color if the experiment is done without dyes.

Ingredients and Procedures

Ingredients
-Around 80 ml hydrogen peroxide (30% concentrated is good)
-40 ml of Dawn dish detergent
-10 to 15 ml of potassium iodide
(measurements vary upon how concentrated the ingredients are, try to use different measurements and see for yourself)

Procedures

-Pour the hydrogen peroxide and the detergent into the cylinder and mix them. If desired, add a few drops of food coloring.
-This is the tricky part. Tip the iodine into the cylinder and stand back. The reaction will take place very quickly, shooting out hot foam.
-Once the reaction has taken place and the foam has cooled, Clean it up with water. (you can also use small embers for fun, the extra oxygen from the experiment makes it glow a lot)

Kid Friendly Way

A more kid-friendly, though less dramatic version can can be created with common household hydrogen peroxide, a packet of dried yeast and dish soap. The reaction takes place more slowly, but it doesn't produce as much heat, and is safe for kids to play with.

External Links

http://chem-toddler.com/factors-affecting-reaction-rate/catalyst/elephant-toothpaste.html
http://www.youtube.com/watch?v=ezsur0L0L1c