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Chemistry · Early Years · The School
Watching ice melt
Put an ice cube on a plate and watch. It goes from hard and cold to a puddle. Nothing was added and nothing taken away — the warmth of the room did it. Put a second cube somewhere cold and compare which melts first.
Water disappearing
Leave a saucer of water out for two days and some of it goes. It has not vanished; it has gone into the air, too small to see. That is why washing dries on a line. Warm, windy days dry washing fastest — ask why.
Still the same water
Ice, water and steam look completely different but they are all the same stuff, just warmer or colder. Freeze the puddle again and you have your ice cube back. Nothing new was made.
Put an ice cube in a saucer and draw round it. Come back in an hour: a puddle, the same water in a different form. Now put the saucer in the freezer and come back later: ice again, and about the same amount. Nothing was added or taken away at any point. If it had turned into something NEW, freezing it would not have brought the ice back.
Where the puddle goes
Water that dries has not disappeared and has not turned into something new. It has become water vapour, which is water spread out so thinly in the air that you cannot see it. You can catch it coming back: breathe on a cold window and the mist that appears is your breath's water turning back into a liquid on the cold glass. That is the same journey run backwards, and it is why a cold drink gets wet on the outside on a hot day — that water came out of the air, not through the glass.