How to blow up a balloon...

How to blow up a balloon...

using yeast!

What you need:

  • A packet of fresh yeast (you can buy this at the supermarket)
  • A small, clear plastic bottle (washed)
  • 1 teaspoon of sugar
  • 2 inches of warm water

What to do:

Fill the bottle up with two inches of warm water. As yeast is a living organism it works best in warm temperatures - a bit like us!

Add all of the yeast and stir gently.

Add all of the sugar and stir gently. The sugar is food for the yeast to eat.

Stretch the balloon out slightly. Place the neck of the balloon over the neck of the bottle.

Leave the bottle in a warm place for around twenty minutes.

When you return it should have started to inflate!

This is because when the yeast feeds on sugar it produces carbon dioxide, which is a gas. The carbon dioxide inflates the balloon. This is the same process that causes bread to rise. You can find out more about yeast and our other microbe friends in our Mighty Microbes article.

If you want to investigate further...

Try leaving different bottles in different rooms. Which temperature produces the biggest balloon?

Try other sugary foods such as treacle, honey and syrup. Which food produces the biggest balloon?