How to blow up a pumpkin

How to blow up a balloon with alka seltzer

What you need to blow up a pumpkin balloon

Small bottle

Alka seltzer


Orange Balloon

Black Sharpie


Blow up the balloon first and then let the air out, draw a pumpkin face on the balloon.

Half fill your bottle with water.

Drop an alka seltzer into the bottle and place the balloon on top.

Watch as the balloon blows up and your pumpkin grows.

Blow up a pumpkin

Why does this happen?

Alka Seltzer contains contain  sodium bicarbonate ( baking soda ) and citric acid. When placed in to 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 just like we see when we add vinegar to baking soda.

AcidBase 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.

Extension Ideas

Can you compare the alka seltzer with an effervescent vitamin tablet? Which blows up the biggest balloon? Think about how you can make this a fair test.

You could also try popping candy or baking soda and vinegar.

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