Popcorn Dance

Not just a snack with a bounce, this activity explores some weighty gases

Australian Curriculum links

• Science > Chemical Sciences > Year 6 > ACSSU095
• Science > Chemical Sciences > Year 9 > ACSSU179

You’ll need

• Clear plastic cup
• Bicarbonate of Soda
• Popcorn kernels
• Vinegar
• Water
• Spoon

Try this

1. Half fill the cup with water and add roughly 1/4 cup of vinegar.
2. Drop about a dozen popcorn kernels into the water and vinegar mixture.
3. Add 1–2 teaspoons of bicarbonate of soda and stir briefly.
4. Watch what happens.

What’s happening?

The popcorn kernels seem to dance, sinking to the bottom of the cup and then rising to the surface again before falling back down. This happens because bicarbonate of soda and vinegar undergo a chemical reaction, producing carbon dioxide gas. Small bubbles of carbon dioxide stick to the uneven surfaces of the popcorn kernels. These carbon dioxide bubbles are less dense than the liquid that surrounds them, so they rise to the surface of the cup (less dense liquids and gases float above more dense liquids and gases). Eventually, enough bubbles will form on a popcorn kernel to pull the popcorn to the surface. When the popcorn reaches the surface the carbon dioxide is released into the air and the popcorn sinks back down to the bottom of the cup again.