Geyser Cola/ Mentos or Soda/ Candy

At first looks like a dangerous and silly prank, but if well done, on the right place is spectacular, and makes all adults want to be restless young minds.

Don't do this at home, chose an easy cleaning place!

What we need:

• 1 coke bottle, full,
• 1 Mentos pack,
• 1 cardboard, enough to "close" the bottle,
• 1 test tube... or a paper funnel,

How to:

1. Chose the place to this demonstration wisely, it will be messy, and you must be able to run away... fast;
2. Uncap the coke bottle;
3. Place all the Mentos (about 10) on the paper funnel, or test tube;
4. If you are using a test tube , place the cardboard on the top and turn the tube upside down;
5. If you are using the funnel close the end with the cardboard;
6. Place the tube/funnel on the bottle uncapped top;
7. Look around and chose a direction to run away;
8. Remove the card quickly, so the candies fall in the bottle.
9. Run!

"Parents friendly" alternative
You can do this on a smaller scale, without the amazing geyser but with same effect, and best of all, without the mess.

What we need:

• 1 glass,
• 1 Mentos pack,
• Coke or other carbonated drink.

How to:

1. Put the glass inside a bowl;
2. Fill half of the glass with your drink;
3. Throw 1 Mentos inside;
4. You don't need the running part.

Results:

Before any further conclusion, 

• What happens isn't a chemical reaction! its a physical phenomenum, witch results in the sudden production of carbon dioxide resulting in a massive bubbling;
•  If we look closer, Mentos surface is very rough... those irregularities are responsible for gas formation and sudden release.
• Soda is made up mostly of water and sugar.

Knowing, these 3 things, lets try to find out what happen:

Carbonic drinks, like coke and other sodas, contain, as its name indicates, dissolved carbon dioxide. This gas is in equilibrium  and under a certain pressure- that’s the key the pressure- ready to escape as soon as the pressure on the liquid surface lower. All we know that’s necessary to remove the cap of the bottle with careful, without shake the liquid, otherwise all the drink will come out the bottle.
Until you open the bottle, the gas remains in suspension on liquid, and it can expand to form bubbles.
Note that if you place the soda in a glass and submerge a toothpick on it, its surface will form bubbles immediately.

Why?
Water molecules attracted each other strongly, holding the gas bubble in a kind of water molecules net. To form a new bubble or to expand the existing bubbles the water molecules must to move away from each other. Extra energy is needed to break this surface tension! In other words the water shows resistance to soda bubble expansion.

In this demonstration Mentos candy is going to perturb the coke equilibrium, the surface tension, this allows the CO2 to escape.

How?
When you drop the Mentos on the bottle the surface tension is disturbed, and therefore the expansion and formation of new CO2 bubbles becomes possible. Mentos have thousands of micro holes on the surface those are called nucleation places- perfect places to form CO2 bubbles. As soon as Mentos touch the soda the bubble formation is initiated in its entire surface.
When all this CO2 is released from the bottle takes the liquid with it.

In conclusion:
This process depends greatly on CO2-under pressure- and on a element that disturb the tension -the element must be porous with nucleation holes), So we can conclude this demonstration can be done with any drink with bubbles like Sprite, beer, or even Red Bull.
We don’t know any other candy that works best then Mentos. They have thousands porous and heavy; they drown and don’t come out with the geyser.



Watch MithBusters movie "MythBusters - Diet Coke & Mentos":


Note that: Internet sources tells us that the use of diet coke works best because the low sugar ratio, witch delays the bubble formation

Sources:
Mentos e Coca-Cola- Ciência Hoje



Et voilá!

Enjoy!