Water

1
Water

• CHEMISTRY 2

Additional Science
Chapter 8
2
The Importance of Water
Water is used widely as a coolant in industrial
processes
Water is essential to life on Earth
Additional Science
75 of the worlds surface is covered by water
Water is used widely as a solvent in industrial
processes
Chapter 8
3
The public water supply
Cl
35
17
Additional Science
Water from river, lake or underground well stored
in a reservoir
Chapter 8
This is the process that takes place to ensure
that we have a supply of drinking water. Some
water authorities add other chemicals to drinking
water e.g. many add fluoride ions which prevent
tooth decay at controlled levels.
4
Hard water
As rain water flows through rocks, it picks up
calcium and magnesium ions. The result is - hard
water.
Hard water forms scale (calcium carbonate) in
pipes, and restricts water flow.
Hard water mixes with soap to form calcium or
magnesium stearate which is insoluble this is
why soap scum forms.
Hard water doesnt produce soap suds easily.
Additional Science
Chapter 8
5
Types of hardness
Additional Science
Chapter 8
6
Disadvantages
Advantages
Hard water
Additional Science
Chapter 8
7
Solubility curves
Terms Solute the substance that dissolves
(sugar). Solvent the liquid doing the
dissolving (water). Solubility mass of solute
that dissolves in a certain mass of solvent.
water
sugar
The sugar doesnt dissolve in the water any
longer you have a saturated solution.
Usually the solubility of a solute increases with
an increase in temperature
Additional Science
Solubility curve
Chapter 8
sodium chloride
Can you think which solutes solubility is most
affected?
Solubility/ g per 100g of water
potassium chlorate
Temperature C