Elephant's+Toothpaste

Materials
= =
 * 2 - 1L graduated cylinders[[image:http://materialscience.uoregon.edu/GK12/elephantstp.jpg align="right" caption="Kari's Elephant's toothpaste demo"]]
 * 3% Hydrogen peroxide (Hmedia type="custom" key="4777263"Omedia type="custom" key="4777265")
 * 30% Hmedia type="custom" key="4777263"Omedia type="custom" key="4777265"
 * Potassium iodide (KI)
 * Dish soap
 * Gloves
 * Goggles
 * Lab coat/apron
 * Garbage bag(s)

=Safety=
 * 30% Hmedia type="custom" key="4777263"Omedia type="custom" key="4777265" will burn your skin! Use caution!

=Preparation=
 * Cover demo area with garbage bags or perform in a clear, plastic box. This demo can be messy!
 * Pour ~50-100mL 3% Hmedia type="custom" key="4777263"Omedia type="custom" key="4777265" into one graduated cylinder and ~50-100mL 30% Hmedia type="custom" key="4777263"Omedia type="custom" key="4777265" into the other.
 * Add a squeeze of dish soap to each. Swirl gently to mix.
 * Make a concentrated solution of KI and water.

=Demo=
 * Add ~20mL KI solution to 3% cylinder. Watch the bubbles slowly rise and spill out of the cylinder.
 * Add the same amount of KI to the 30% cylinder and stand back! This reaction goes much more quickly!

=Explanation= The potassium iodide catalyzes the decomposition of the hydrogen peroxide into water and molecular oxygen (Omedia type="custom" key="4777263"). Also, you may notice an orange/brown color appear when you do this reaction. The color is from the iodine (Imedia type="custom" key="4777263") that is formed when some of the peroxide oxidizes iodide ions. Because oxygen bubbles are formed during the reaction you can actually insert a lit (or freshly blown out) stick into the bubbles and watch it flare up slightly (sorry, no major explosions).

=Clean up=
 * Graduated cylinders can be rinsed in a sink using lots of water.
 * Trash bags can be thrown away.
 * This reaction produces iodine as a side product, so be sure to wipe up any spills quickly, before it can stain.