Diet Coke and Mentos Explosion: How does it work?
Although there are a few different theories around about how this experiment works, the most favored reason is because of the combination of carbon dioxide in the Diet Coke and the little dimples found on Mentos candy pieces.
The thing that makes soda drinks bubbly is the carbon dioxide that is pumped in when they bottle the drink at the factory. It doesn't get released from the liquid until you pour it into a glass and drink it, some also gets released when you open the lid (more if you shake it up beforehand). This means that there is a whole lot of carbon dioxide gas just waiting to escape the liquid in the form of bubbles.
Dropping something into the Diet Coke speeds up this process by both breaking the surface tension of the liquid and also allowing bubbles to form on the surface area of the Mentos. These candy pieces are covered in tiny dimples (kind of like golf balls), which increase the surface area and allows a large amount of bubbles to form.
Vinegar and Alka-Seltzer tablets: How does it work?
Carbon dioxide gas builds up so much pressure inside the film canister that the lid is forcibly launched. With an Alka-Seltzer tablet, the CO2 is produced as a result of a chemical reaction.
The fizzing you see when you drop an Alka-Seltzer tablet in water is the same sort of fizzing that you see when you mix an Alka-Seltzer tablet and vinegar. The acid mixes with the sodium bicarbonate (baking soda) to produce bubbles of carbon dioxide gas. If you look at the ingredients of Alka-Seltzer, you will find that it contains citric acid and sodium bicarbonate (baking soda). When you drop the tablet in vinegar, the acid and the baking soda react to produce carbon dioxide gas. The gas keeps building up until finally the top pops off. The lid of the canister is the path of least resistance for the gas pressure building up inside, so it pops off instead of the stronger sides or bottom of the canister bursting open.
When the build up of carbon dioxide gas is too great and the lid pops off, Newton's Third Law explains why the film canister flies across the room: for every action there is an equal and opposite reaction. The lid goes one way and the film canister shoots out of the tube in the opposite direction.
Elephant Toothpaste: How does it work?
Foam is awesome! The foam you made is special because each tiny foam bubble is filled with oxygen. The yeast acted as a catalyst (a helper) to remove the oxygen from the hydrogen peroxide. Since it did this very fast, it created lots and lots of bubbles. Did you notice the bottle got warm. Your experiment created a reaction called an Exothermic Reaction - that means it not only created foam, it created heat! The foam produced is just water, soap, and oxygen so you can clean it up with a sponge and pour any extra liquid left in the bottle down the drain.
This experiment is sometimes called "Elephant's Toothpaste" because it looks like toothpaste coming out of a tube, but don't get the foam in your mouth!
Below, use evidence to show what kind of change each of these demonstrations was. Use as many pieces of evidence that you observed.
Diet Coke and Mentos Demonstration:
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Alka-Seltzer and Vinegar Demonstration:
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Elephant Toothpaste Demonstration:
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