For you to do
You'll put vinegar in a bottle and baking soda in a balloon, then tip the balloon up so they mix. The reaction makes carbon-dioxide gas that inflates the balloon by itself.
Grown-up help
All on your own — just work over a sink or tray.
Run it
- Pour a few centimeters of vinegar into the bottle.
- Use the funnel to put 2 spoons of baking soda into the balloon.
- Stretch the balloon over the bottle's mouth WITHOUT letting the powder fall in yet. Then lift the balloon so the baking soda drops into the vinegar.
Test a variable
Do it again with twice the baking soda, or twice the vinegar — change only one. Measure the balloon (wrap a string around it). What makes the biggest balloon?
What's happening
Baking soda and vinegar undergo a **chemical reaction**: their **atoms** rearrange into new **molecules**, including carbon-dioxide gas, which fills the balloon. Past a certain point adding more of one ingredient stops helping — because the other one runs out. Changing one **variable** at a time is how you find that point.