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When solids get hot enough, they melt
and become liquids. When liquids get
cold enough, they freeze and become
solid. This is called changing states and
it happens to all kinds of substances.
Changing states
Changing states of water
Water exists as a solid, liquid, or gas. You can find
all three forms of water in your home. They are ice,
water, and steam (water vapour).
Why does chocolate become soft and gooey in your mouth?
Science and technology
Liquid metal
Every substance melts
and boils at a particular
temperature (its melting
and boiling points). Most
metals are solid at everyday
temperatures because they
have a high melting point.
But mercury has such a low
melting point that it is liquid
even at room temperature.
Ice is solid water. It forms
when liquid is cooled until
it freezes. Each piece of ice
has a definite shape.
Rivers of iron
Iron must be heated in
a furnace to make it melt.
Molten iron is so hot it glows
white. It is poured into a
mould and left to harden
to make solid iron objects.
When ice is warmed, it melts
and becomes liquid and
takes on the shape of the
container holding it.
As water is heated, bubbles
of steam form. They rise to
the surface and burst, so
steam escapes into the air.
Condensation
As water vapour in the air
is cooled, it changes into
liquid water. This is called
condensation. You can see
it on the outside
of a cold bottle.
When water
vapour in the
air touches a
cold bottle, it
condenses into
tiny drops of
liquid.
