Temperature and Water
States of water and the water cycle
Tell the three states of water apart by how they behave, name the changes between them, and follow water round the water cycle.
Ice, water and water vapour look like three different things, but they are one substance wearing three faces. We call those faces states. Ice is the solid state, the water you pour is the liquid state, and water vapour — invisible, and already in the air around you — is the gaseous state.
Telling the three apart
Ice holds its own shape wherever you put it. Water has no shape of its own, so it takes the shape of its container. Water vapour does neither — it spreads out into the whole of the space it is given.
The four changes, by name
Solid to liquid is melting. Liquid to solid is freezing. Water to vapour is evaporation. Vapour back to liquid is condensation. Heating drives the first and the third; cooling drives the other two.
Have a play
The stages water passes through on its way from the ocean and back again.
Tap any part of the picture.
Worked example
A glass of cold water is left on the table, and after a few minutes its outside is wet. Where did that water come from?
Rule out the easy answer first: mark the water level inside the glass and watch it. It does not drop.
If the water had seeped through the glass, the level inside would have fallen. It did not, so the wetness came from outside the glass.
Try it together
Now work out why water kept in an earthen pot goes cold, when the same water in a steel pot does not.
An earthen pot has tiny gaps in its wall that a steel pot does not have. Take it a step at a time.
1.Water seeps into the pot's wall and reaches the outside surface, where the air gets at it. Which change of state happens to that water?
Have a go
Have a go on your own. The amount of water vapour held in the air has a one-word name, and the weather report gives it daily. What is it?
Ready to practise?
Eight questions on what you have just read. Nothing is timed, and you can play as many times as you like.