Yeast Is Alive

Big question: How can a spoonful of yeast blow up a balloon?

Feed yeast warm water and sugar in a bottle, then watch the balloon your grown-up stretches over the top fill up by itself.

What you need

• 1 packet (2 1/4 teaspoons) active dry yeast
• 1 tablespoon sugar
• 1 cup warm water
• A clean, empty plastic bottle
• A balloon
• A funnel (a cone that helps you pour into a small opening)

What to do

1. Warm waterWash your hands first and check every ingredient with your grown-up. Your grown-up fills a cup with warm tap water. It should feel like a warm bath on your wrist, not hot.
2. Feed the yeastUse the funnel to pour the yeast, the sugar and the warm water into the bottle. Swirl it gently to mix.
3. Add the balloonHold the bottle steady on the table while your grown-up stretches the balloon over the top. Only your grown-up handles the balloon, and nobody puts it in their mouth. Set the bottle somewhere warm, like a sunny windowsill, away from the stove.
4. Watch and sniffCheck the bottle every 5 minutes. Look for bubbles and foam, and watch the balloon start to puff up. Leave the balloon on until the very end. Then your grown-up takes it off, and you can take a gentle sniff of the bottle for a bready smell.
5. See it riseAfter 20 to 30 minutes the balloon should stand up. Nobody blew into it, so what filled it?

What is happening?

Yeast is made of tiny living things, each far too small to see on its own. One packet holds a huge number of them. Warm water wakes them up, but hot water can kill them. They eat the sugar and give off carbon dioxide gas, which fills the bottle and pushes into the balloon. In bread dough, that gas gets trapped and makes the dough rise. Muffins rise faster from baking powder bubbles instead.

Do not drink the yeast water. Balloons can choke children under 8, so only your grown-up handles the balloon, and nobody puts it in their mouth. If it pops, your grown-up picks up every piece and throws it away at once. When you finish, your grown-up takes the balloon off and throws it away. Some balloons are latex, and some people are allergic to latex, so your grown-up checks for latex allergies first.

Try it

• 
  Little Helpers

  Vanilla Blueberry Muffins

• 
  Little Helpers

  Dairy-Free Vanilla Muffins

Check yourself