Description

A small amount of water and a piece of an Alka-Seltzer^® tablet are placed in a plastic film canister. The lid is quickly snapped on and the canister turned upside down. Within a few seconds the canister explodes with a loud pop, sending the bottom of the canister flying through the air.

Explanation

Alka-Seltzer and other effervescent tablets contain sodium bicarbonate (NaHCO₃), a base, and citric acid (C₆H₈O₇), an acid. (They also contain acetylsalicylic acid (aspirin) as a pain reliever, but it is not involved in making the fizz.)

In the solid tablet the acid and base do not react, but when placed in water the sodium bicarbonate reacts with the citric acid in an acid-base neutralization reaction. One of the products is carbon dioxide gas, which causes the fizz.

NaHCO₃(aq) + C₆H₈O₇(aq)NaC₆H₇O₇(aq) + H₂O(l) + CO₂(g)

How can I do it at home?

An adult must be present. 

1. Put a small amount of water into a film canister (Fuji film canisters work better than Kodak) 
2. Put a small piece of an Alka-Seltzer^® tablet in the film canister.
3. Put the lid on, turn the canister upside down and STEP BACK!!!

What would happen if...

• you tie a ribbon to the canister, can you figure out how high it flies?
• you try adding more or less water?
• you try adding more or less Alka-Seltzer^®?
• you try adding hot water or cold water?

want to try some cool experiments with Alka-Seltzer? Click here.

still have questions?  email us!

explanation furnished by UCCS's Dr. David Anderson