Wet and dry
Chemistry · Early Years · The School
Wet or dry
Some things are WET and some things are DRY. A puddle is wet. A towel out of the wash is wet. Sand at the top of the beach is dry, and sand at the edge of the sea is wet. You can tell by touching, and you can often tell by looking — wet things usually look darker.
Some things drink it up
Pour a little water on a paper towel and it soaks straight in. Pour it on a plastic tray and it sits in a puddle on top. Materials that soak water up are ABSORBENT. Sponges, cloths, paper and cotton are absorbent. Plastic, metal and glass are not, so we use them to hold water.
Getting dry again
Wet things become dry when the water goes into the air. That is why washing dries on a line, and why a wet coat dries near a warm radiator. It happens faster when it is warm, and faster when it is windy. The water has not disappeared — it has gone into the air where we cannot see it.
Put a saucer of water inside a large glass jar and screw the lid on tight. Put it somewhere sunny. Over a day the water in the saucer drops — but droplets appear on the inside of the glass, and if you tip them back you get water again. Nothing could get in or out of the sealed jar, so the water never disappeared. It went into the air and came back on the cold glass.