CurioXLStart free

Slow Changes: Rust and Brown Apples

What you’ll find out

Start this lesson — free

No sign-up and no real names. In the lesson you check your understanding as you read, run the experiment yourself, and practise until it sticks.

Changes that happen on their own

Some changes happen slowly, all on their own. Leave an iron nail in water for a few days and it turns orange-brown and flaky. That is rust. A nail kept dry stays shiny. Rust needs both water and air, and it cannot be undone.

Slowing a change down

Cut an apple in half and leave it out, and soon the cut side turns brown. Air is changing it. Squeeze lemon juice on another cut apple and it stays pale much longer. The lemon juice slows the change down.

Curriculum links: NGSS 2-PS1-4 · NGSS 5-PS1-4