Science Saturday - Make Your Own Mentos Fountain

Make Your Own Mentos Fountain

Supplies:

Two Index cards

Cellophane Tape

2-liter bottle of diet soda

Roll of Mentos candy - Use 5 candies from the pack.

Steps:

1. Roll one of the index cards into a tube as wide as the opening of the bottle. Tape the index card tube to hold it's shape. Open the bottle of soda and set the bottle on the ground outside; be careful not to tip it over.

2. Stack the Mentos in the index card tube. Place teh second index card on top of the tube and turn the tube upside down. Place both on top of the opening of the bottle so that the tube is just over the opening, with the flat index card in between holding the Mentos from falling in.

3. Pull out the index card and let the Mentos slide into the soda. Stand Back!

4. Try some variations. The fruit variety of Mentos is smoother that the mint; which makes a bigger fountain? Is there a difference between regular and diet soda? Do other candies work as well as Mentos?

What is Happening?

         Big chemical reaction, right? Probably not. That soda whooshing out of the bottle is likely not a chemical reaction at all. A chemical reaction happens when molecules break apart and combine into new ones, and that doesn't seem to be happening here. Changes can come from other physical forces, though.

Soda is bubbly because it contains carbon dioxide - a gas - dissolved in water. That carbon dioxide was dissolved into the soda at the factory under high pressure. Water molecules are strongly attracted to each other and they surround the carbon dioxide, preventing the carbon dioxide molecules from coming together to form bubbles. You can't see the carbon dioxide in a closed bottle, but when you open the bottle, you can see bubbles form because you have reduced the pressure, and the carbon dioxide comes out of the solution.

         When you shake the bottle, the carbon dioxide gas molecules can come together and form bubbles. Then, when you open the bottle, the carbon dioxide whooshes out of the bottle and takes some of the soda with it.

         The Mentos have a similar effect to shaking a soda bottle. They allow gas bubbles to form. Remember, the carbon dioxide molecules are surrounded by water molecules that trap them. Once a bubble forms, it can grow very quickly; the trick is for the bubble to form in the first place. The surface of an object provides a place where a few carbon dioxide molecules can get together away from the water molecules. Once a few come together, others quickly follow. If you could look at a Mentos candy under a microscope, you would see that its surface is very uneven, with lots of nooks and crannies. These are the perfect place for LOTS of bubbles to form.

         This isn't a chemical reaction where molecules are breaking apart and forming new ones. It's a physical process. The surface of the Mentos candy is simply helping the carbon dioxide gas molecules come together. There may also be some ingredients in the soda and Mentos that help this process ass well, but the main factor seems to be the surface of the Mentos. When you drop the Mentos candies into the soda, they fall to the bottom, forming bubbles along the way. The bubbles form very quickly and also rise to the surface very quickly, taking lots of soda with them. Whoosh!

Video:

If you are unable to do this experiment on your own then take a look at this video to see various reactions.

Have Fun . . .

http://youtu.be/iS2vG1o7Op4