Blow up a balloon with Alka Seltzer – valentine style

This fun Valentine’s Day themed science experiment is a fun twist on the traditional blowing up a balloon with Alka Seltzer activity.

The idea is that you add something that produces gas to a bottle with a balloon on top. The gas first fills the bottle and then the balloon, blowing it up.

It’s a great way to demonstrate how gases spread out to fill all the available space!

I used an Alka Seltzer, but effervescent vitamin tablets also work really well.

How to blow up a balloon with Alka Seltzer

What you need

Small bottle

Alka Seltzer

Water

Balloon

Felt tip pen/sharpie

Method

Blow up the balloon first and then let the air out, and draw a small heart on the balloon.

Fill the bottles or jars with water, leaving a gap at the top.

Drop the Alka Seltzer into the bottle and quickly place the balloon on the top.

Watch as the balloon blows up and your heart grows.

 

Extension tasks

Can you think of anything else you could use instead of Alka Seltzer? We tried to blow up a balloon with popping candy with some interesting results, but baking soda and vinegar would be another good investigation.

Why does the balloon blow up?

Alka Seltzer contains sodium bicarbonate ( baking soda ) and citric acid. When you drop a tablet into water, it forms sodium citrate, water and carbon dioxide, which are the bubbles of gas you see. The bicarbonate of soda reacts with the citric acid. This is an acid–base reaction like we see when we add vinegar to baking soda.

Acid-Base Reactions

 If you place an acid and a base together, they react to neutralise each other, producing a salt. The H(+) cation of the acid combines with the OH(-) anion of the base to form water.

More experiments using alka seltzer

Make a fizzy lava lamp. These are great as they can be used over and over again.

A film canister rocket is a brilliant science activity. They fly up with a lot of force, so remember to stand back!

Last Updated on January 30, 2025 by Emma Vanstone