coke and mentos eruption

Explanation

There are various theories that are debated as to the exact scientific explanation of the phenomenon; all scientists claim that it is a physical reaction and not a chemical one.To form a new bubble, water molecules must push away from one another. It takes extra energy to break this surface tension. So, in other words, water resists the expansion of bubbles in the soda.

Each Mentos candy has thousands of tiny pores all over its surface. These tiny pores function as nucleation sites for carbon dioxide bubbles to form. As soon as the Mentos enter the soda, bubbles form all over their surface. They quickly sink to the bottom, causing carbon dioxide to be released by the carbonated liquid with which they come into contact along the way.

The reaction was the subject of an August 9, 2006 episode of MythBusters, a popular television program on the Discovery Channel. They concluded that the caffeine, potassium benzoate, aspartame, and CO2 gas contained in the Diet Coke and the gelatin and gum arabic ingredients of the Mentos all contribute to the jet effect. In addition, the MythBusters theorized that the physical structure of the Mentos is the most significant cause of the eruption. When flavored Mentos with a smooth waxy coating were tested in carbonated water, no reaction occurred, whereas standard Mentos added to carbonated water formed a small eruption, by their claim, affirming the nucleation-site theory. This was further supported when rock salt was used as an effective substitute for Mentos. The experiment was also repeated in an episode of Numb3rs. (source:www.wikipedia.com)