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Experimentbeginnerdraft

Yeast blows up a balloon

Also searched as: yeast experiment for kids, yeast balloon bottle

In short: Yeast makes so much gas that it can blow up a balloon.

Picture it

Like a tiny bellows made of billions of yeast cells: each one breathes a little, and together it is enough for a balloon.

Before · Afterstart
lukewarm water
cold water
Schematic
You need · 45 minutes
  • a packet of dried yeast
  • 2 tsp sugar
  • lukewarm water
  • a small bottle
  • a balloon

How it’s done

Sequence · Step 1 of 3
123

Put yeast and sugar in the bottle and add about a third of lukewarm water.

All steps as a list
  1. Put yeast and sugar in the bottle and add about a third of lukewarm water.
  2. Swirl, then pull the balloon over the neck of the bottle.
  3. Put it somewhere warm and wait.

What you see

After 20–40 minutes it foams in the bottle, and the balloon stands up and inflates.

Why it happens

The eats the sugar and gives off carbon dioxide. The same gas blows up the holes in bread dough. With cold water it takes much longer.

Related entries
Yeast fermentation
Sources · 1
  • Harold McGee: On Food and Cooking (2004)