States of Matter — Answer Key
Part A: Sort the Words
Sort each word or number into the correct category box.
1. Decide if each change can be undone (reversible) or cannot be undone (non-reversible).
Reversible
water freezing into icebutter meltingice cream meltingchocolate melting Non-Reversible
egg cooking in a panpaper burningwood turning to ashbread toasting Freezing and melting can be undone by heating or cooling. Cooking, burning, and toasting change the item forever.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. When water freezes into ice, the change is reversible.
Ice can melt back into water, so freezing is a change you can undo.
2. Cooking an egg is a non-reversible change that cannot be undone.
Cooking changes the egg forever, so it cannot return to its raw form.
3. Melting butter on toast is a reversible change.
Butter melts when warm and becomes solid again when it cools, so it can go back.
4. When paper is burned, it turns into ash and smoke.
Burning releases smoke (a gas) and leaves ash behind, which cannot become paper again.
5. Ice cream melting in the sun is a reversible change.
Melted ice cream can refreeze into a solid, so the change can be reversed.
Part C: True or False?
Read each statement. Circle True or False.
1. Freezing and melting are reversible changes.
True False
You can switch between solid and liquid many times by heating and cooling.
2. Toasting bread can be undone to make fresh bread again.
True False
Toasting is non-reversible because the bread is changed by heat forever.
3. Melted chocolate can harden again when it cools.
True False
Chocolate melts with heat and becomes solid when cool, so it is reversible.
4. Burning wood is a reversible change.
True False
Burning is non-reversible; wood turns to ash and smoke that cannot become wood again.