Quick Experiment “Volcanic Diet Coke”

• 1 x Steve Spangler Geyser Tube
• 1 x Packet of Mentos
• Camera!

1. Unscrew the cap of a bottle of Diet Coke and attach the geyser tube.
2. Place the bottle on a level surface and pull the pin!
3. Watch how high the geyser goes.
4. How about try and compare two bottles of Diet Coke. One that is warm and the other that is cold. Does temperature affect how fast the gas is released (and thus the height of the geyser)?

• Be careful when moving away from the geyser. Don’t trip.

This experiment examines physical changes, pressure and how temperature affects the solubility of gases in a liquid.

The reason soft drink is fizzy is because there is carbon dioxide gas in the liquid. This gas is dissolved into the liquid under high pressure when the bottles are made. Undoing the top can cause the gas to come out and make the drink fizzy. BUT, small divots (called nucleation sites) on the side of the bottle also do this.

A Mentos tablet has sugar on its surface and this acts like tiny little divots (like a golf ball has divots or dimples). When the Mentos enters the soft drink, these dimples allow the formation of carbon dioxide gas. The sudden formation of carbon dioxide gas causes an increase in pressure inside the bottle which forces the drink out and up through the geyser tube.

Check out in more detail what is going on and how you can explore variables (temperature, liquid type, surface areas etc) in our Gigantic Mentos Geyser experiment guide. (supplied with purchase)