Science · Stage 6

Changes You Can Undo — and Changes You Can't

Melting, dissolving and bending can be undone. Burning, rusting and cooking make something new. How do you tell them apart?

✦ Science📘 Stage 6 · S6⏱ ~12 min🧒 Ages 10–12★ Free to start

I can tell reversible changes from changes that make a new substance.

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Kavi's Kitchen Experiments

In the kitchen, Kavi melts a chunk of chocolate 🍫 into a glossy puddle — then pops it in the fridge and, ta-da, it hardens right back! "That's a reversible change," hoots Kavi. "Same chocolate — I just changed it back." But when a slice of toast 🍞 pops up brown and crispy, Kavi frowns: "I can't un-toast this — the bread has turned into something new!" Some changes you can undo… and some make a brand-new substance. Come and learn to tell them apart!

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What your child will learn

1Reversible, or a new substance?In a reversible change the stuff stays the same — you can change it back. A new-substance change cannot be undone. Tap the right box for each one.

2Same stuff, or something new?Two changes caused by heat — but only one can be undone. Tap each card.

3Clues that a NEW substance has formedWhen a change makes something new, it usually leaves clues. Tap each clue to learn it.

4Can you get it back?Decide if each change can be undone, then tap to check. Tap Next test for more.

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A peek inside

Kavi melts a chocolate bar in a warm bowl, then puts it in the fridge until it is hard again. Is this a reversible change, or has a new substance been made?

The chocolate only went from solid to liquid and back to solid. No new substance was made — it is still chocolate — so the change can be undone.

Try this at home: What is a reversible change?

Ready to play and learn?

Start the free interactive lesson, or print the handout for screen-free play.

Start the free lesson →⬇ Download PDF

Part of Science · Stage 6 · S6 on KAVI Academy — a secular, whole-child learning platform for ages 5–12.