Zosia made the ice cube herself. She froze water in a tray.

So the ice cube was water, frozen.

Now it has melted. The liquid in the cup is water: the same water.

Zosia puts the cup in the freezer. The water freezes: ice again.

Ice melts into water. Water freezes into ice. The same water, round and round.

Now she lets the water evaporate. It is water vapor in the air: still water.

The water vapor touches a cold window and condenses: drops of water again.

Ice, water and water vapor: the same stuff, water, going round. Melting, freezing, evaporating, boiling, condensing.

Ice, water and water vapor are the same stuff: water. Scientists say the same matter.

Bertie was not right. Melted ice is plain water.