Success Homeschool

Year 7 Science · Reversible and irreversible changes

Name: ______________________

Date: ____________

1. Which change is reversible?
- ☐ (a) Burning toast
- ☐ (b) Melting ice
- ☐ (c) Frying an egg
- ☐ (d) Rusting a nail
2. Which is a sign that a new substance has formed?
- ☐ (a) A change of shape
- ☐ (b) Melting
- ☐ (c) Bubbles of gas being produced when two substances mix
- ☐ (d) Cutting into pieces
3. How can you get salt back from salty water?
- ☐ (a) Let the water evaporate
- ☐ (b) Freeze it
- ☐ (c) Stir it more
- ☐ (d) Add more water
4. Baking a cake is irreversible because…
- ☐ (a) It gets hotter
- ☐ (b) It changes shape
- ☐ (c) It gets softer
- ☐ (d) New substances form and you cannot get the eggs and flour back
5. Which pair are both reversible changes?
- ☐ (a) Burning and rusting
- ☐ (b) Melting and dissolving
- ☐ (c) Cooking and burning
- ☐ (d) Rusting and baking
6. Which gas makes the bubbles when bicarbonate of soda and vinegar mix?
7. Is burning a piece of paper reversible or irreversible?
8. Water freezing into ice is a reversible or irreversible change?

Answer sheet

1. Melting ice — Melted ice can be frozen again.
2. Bubbles of gas being produced when two substances mix — Gas being produced (when nothing is boiling) shows a new substance has formed.
3. Let the water evaporate — When the water evaporates, the salt is left behind.
4. New substances form and you cannot get the eggs and flour back — Baking makes new substances; the ingredients cannot be separated again.
5. Melting and dissolving — Melting and dissolving can both be reversed.
6. carbon dioxide — The reaction produces carbon dioxide gas.
7. irreversible — Burning forms ash, smoke and gases; you cannot get the paper back.
8. reversible — Ice can be melted back into water.