comes from peat
or igneous rock
sources, such as
granite but may
also come from
sandstone sources,
since such
sedimentary rocks
are usually low in
calcium and
magnesium.
Permanently Hard
Water
Caused by the presence of
dissolved calcium sulfate
CAN BE SOFTENED BY:
Adding washing
powder (sodium
carbonate)
The added carbonate
ions react with the
calcium and magnesium
ions. The calcium and
magnesium ions are no
longer dissolved in the
water.
Running
water through
'ion exchange
columns'
The columns
have
sodium/hydrogen
ions and
exchange them
for the calcium
and magnesium
ions in the water
Hard Water
The scum produced
is insoluble
Forms scale when heated
Acts as a
thermal insulator
so a kettle (for
example)would
take longer to
boil
The build up
eventually
results in the
blocking of
pipes
This reduces
the efficiency of
the appliance,
therefore they
will need to be
regularly
replaced;
costing money
Calcium ions are good
for healthy teeth and
bones. People drinking
hard water are less at
risk of developing heart
disease
Calcium and
magnesium ions
make the water 'hard'
The calcium
and magnesium
ions are
dissolved from
rocks (such as
limestone, chalk
and gypsum) as
magnesium
sulfate and
calcium sulfate
Temporarily Hard
Water
CAN BE SOFTENED BY:
Adding washing
soda (sodium
carbonate)
The added carbonate ions react
with the calcium and magnesium
ions. The calcium and
magnesium ions are no longer
dissolved in the water
Running water through
'ion exchange columns'
The columns have sodium
(or hydrogen) ions and
exchange them for the
calcium and magnesium
ions in the water
Caused by the presence
of hydrogencarbonate
ions
Removed by boiling
The hydrogen-carbonate ions
decompose to form calcium carbonate
which is insoluble. This is called
limescale.