The elephant toothpaste reaction is a chemical reaction that produces a large foamy mess that looks like toothpaste squirting out of a tube, hence the name. The reaction is caused by the rapid decomposition of hydrogen peroxide (H2O2) using potassium iodide (KI) or yeast and warm water as a catalyst. The reaction produces oxygen gas, water, and iodine, which is why the foam has a yellow color. The foam is oxygen-filled bubbles that result from the hydrogen peroxide being broken down into water (H2O) and oxygen (O2). Adding a little dish soap provides additional surface tension, allowing the bubbles to get trapped and creating lots of foam. The reaction is exothermic, meaning that it releases heat as it occurs. The elephant toothpaste reaction is often used as a fun and engaging science experiment for children to observe a chemical change by combining a yeast mixture with hydrogen peroxide and dish soap.