What’s Really Happening?

When the chalk touches the vinegar, tiny bubbles begin to appear.

Those bubbles are carbon dioxide gas — evidence that a chemical reaction is taking place.

Chalk is mostly made of calcium carbonate. The acid in vinegar reacts with the calcium carbonate, producing new substances and gradually breaking down the chalk.

That is why the chalk can lose mass, become smaller and develop a rougher surface.

Why Does This Matter?

Calcium carbonate is also found in limestone and marble, materials used in buildings, monuments and statues.

Rain is normally only slightly acidic, so it does not attack stone as dramatically as vinegar does.

But over many years, repeated exposure to acidic water can slowly wear calcium-carbonate stone away.

Scientists study these changes to understand weathering and how pollution and the environment can affect buildings, statues and natural landscapes.

Curious Minds Want to Know…

• Would lemon juice change the chalk too?

• Does temperature affect how quickly the reaction happens?

• Does a stronger acid cause a bigger change?

• What happens if the chalk is exposed for longer?

Try next

• See the same calcium carbonate reaction in a much more dramatic explosion → [The Volcanic Eruption]

• Find out what acid does to the calcium inside an actual bone → [The Bone Bender]