100
WATER
- Unlike most compounds, water can exist in all
three states of matter, solid, liquid, and gas, within
Earth’s normal range of temperatures. - At sea level, water is liquid between 0 and
100°C (32–212°F), but below 0°C (32°F), it solidifies
into ice, and above 100°C (212°F), it becomes
gaseous water vapour. - Unlike most other substances, water is denser
when it is liquid than when it is solid – that is why
ice floats on the top of water instead of sinking. - When water freezes into ice, it expands by
nine per cent of its volume with a force that
can burst pipes and split rock. - Earth is the only place in the Solar System where
conditions allow water to exist in liquid form at the
surface. Some liquid water exists under the surface
of the moons of Jupiter and Saturn. - Water is essential for life, so astronomers look for
it when searching for life on other planets. - The body of an average adult man contains more
than 40 litres (70 pints) of water. - You need about 2 litres (4 pints) of water every
day to keep healthy. - About 30 per cent of the world’s population do
not have clean, safe running water at home. - Water is not a resource that can be used up
like oil. Water evaporates into the air, forms
clouds, and falls back to Earth as rain. In areas
of Earth that receive little rainfall, water can
be a scarce resource.
Water is a tasteless, odourless liquid.
Although it appears to be colourless, in fact
it is very pale blue. Each molecule of water
is made up of two hydrogen atoms and
one oxygen atom, giving it the chemical
formula H 2 O. Water is Earth’s most common
compound, found everywhere, from the
oceans that cover 71 per cent of the planet
to each cell of every living organism.100_101_Water.indd 100 03/01/19 12:10 PM