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The world around us
The amount of water on Earth never changes. But it does change state.
•
When we heat ice, which is solid water, it turns into liquid. This is called
melting
.
•
When we heat liquid water it turns into its gaseous state, which is called
water vapour
or
steam
. This
is called
evaporation
. When seawater evaporates into the atmosphere it loses its
salt
and becomes
fresh water vapour.
It can also change back by cooling.
•
When water vapour cools, it turns back into a liquid. This is called
condensation
.
•
When liquid water freezes it turns into ice, which is solid water.
These different states occur in the constant round of changes known as the
water cycle
.
Can we drink
seawater?
1
Test your partner.
a)
Name two places we find fresh water.
b)
Which are the different states of water
in the pictures?
R E A D & T H I N K
The hydrosphere
All the water on the Earth is called the
hydrosphere
. About 96% of the hydrosphere is salt water. Only 2.5%
of the Earth’s water is fresh water. There’s less fresh water, but it’s found almost everywhere! Fresh water
is the water we use for drinking and washing. It’s found in the atmosphere. We can see it in clouds.
We also find fresh water on the surface in the
ice caps
and in rivers and lakes. Fresh water is also found
under the ground in groundwater.
The ice caps are the Earth’s frozen areas.
ice caps
surface freshwater
water vapour
