This document summarizes key information about water, including its physical characteristics, composition, states of matter, solutions, water purification methods, water supply systems, and sustainability. It describes water's unique properties like surface tension, capillary action, and boiling/freezing points. Water is made of H2O molecules and can dissolve many substances as the universal solvent. Solutions are classified by concentration levels. Water purification removes impurities through methods like boiling, filtration, distillation, and chlorination. Water supply systems involve treatment and distribution to consumers after collection from sources. Conservation and pollution control help ensure sustainable water resources.

1. Chapter 5-Water
and Solution
5.1 Physical Characteristics of
Water
What are the physical characterisitics of
water ?
Surface tension of water
Due to strong cohesive forces between the
molecules of water at the surface
Capillary action of water
Is due to cohesive forces between water
molecules and adhesive forces between
water molecules and the surface they come
in contact with
Capillary attraction
Example : A concave meniscus on the
surface of water
Capillary repulsion
Example : A convex meniscus on the
surface of mercury
Boiling point = 100 degree celsius
Density (at 4 degree celsius) = 1 g cm(
negative 3)
Odourless,tasteless and colourless
Freezing point = 0 degree celsius
Surface tension (at 10 degree celsius) = 0.
074 N m(negative 1)
Produces capillary action
Water changes its states when it absorbs
and releases heat
Composition of water
One molecule of water consists of two
hydrogen (H) atoms and one oxygen (O)
atom.
The chemical formula for water is H20
Water is a compound that can be broken
down by electrolysis
Electrolysis
During electrolysis , oxygen is released at
the anode whereas hydrogen is released at
the cathode
What are the effects of impurities on water
Lower the melting point of ice
Increases the boiling point of water
Increases the density of water
Increases the surface tension of water
Change the smell , taste and colour of water
Evaporation of water
Meaning : Process whereby water changes
to water vapour at any temperature lower
then the boiling point of water
Occurs only on the surface of water
What are the factors that affect the rate of
evaporation of water ?
Movement of air
Surrounding temperature
Humidity
Exposed surface area of water
What are the applications of evaporation of
water in everyday life ?
Drying wet hands
Cooling the body
Producing milk powder
Drying rubber sheets
Preserving food
Reducing evaporation of water from the soil
5.2 Solution and Rate of
Solubility
Solute,solvent and solution
Solute A substance that dissolves in a liquid
Solvent A liquid that can dissolve a solute
Solution
A mixture formed when a solute dissolved
in a solvent
Characteristics
Evenly dispersed
Homogenous
Physical methods
No residue
Transparent and clear
No sediment
Types of solutions
Dilute solution
Contains small amount of solute
Can still dissolve a lot more solutes
Does not contain undissolved solute
Concentrated solution
Contains a lot of solute
Can still dissolve small amount of solute
Does not contain undissolved solute
Saturated solution
Contains the maximum amount of solute
Cannot dissolve any more solute
Excess undissolved solute settles to the
bottom
Undissolved solutes in a saturated solution
can be dissolved by heating or adding more
solvent into the solution
Solution and suspension
The mixture of two substances can form
either a solution or a suspension ,
depending on the types of substances that
are mixed together
Solubility
It can be expressed in the unit of gram per
100ml of solvent (g/100ml)
Rate of solubility
The faster the solute dissolves,the higher
the rate of solubility
Factors
Temperature of solvent
Rate of stirring
Size of solute
What is a colloid ?
Meaning : Mixture of two or more solutes
that disperse evenly in a solvent
Types of colloids
Emulsion
Foam
Gel
Water is a universal solvent
Water can dissolve a lot of substances
compared to other types of solvents
Solutions that use water as solvent are
called aqueous solutions
What are organic solvents ?
Meaning : Organic solvents are non-water
based solvents.Organic solvents are carbon-
based solvents
Most of them have properties like volatile ,
carcinogenic , combustible , toxic
5.3 Water Purification and Water
Supply
Water purification method
Boiling
Kills harmful microorganisms
Filtration
Removes suspended particles
Distillation
Produce distilled water (pure water)
Chlorination
Kills microorganisms
Ozonisation
Kills microorganisms
Ultraviolet radiation
Kills microorganisms
Ultra-filtration
Remove impurities , suspended particles ,
viruses and bacteria
Methods to overcome water shortages
Recycling of water
1. Domestic wastewater is treated
2. Microfiltration removes microscopic
particles , including some bacteria
3. Reverse osmosis removes contaminants
in the water
4. Ultraviolet light kills microorganisms .
Then chemicals are added to restore the pH
balance of water
5. Recycled water
Harvesting water from fog and dew
Fog is condensed into liquid on the surface
of the nylon mesh
Obtaining freshwater from seawater
through reverse osmosis
Water supply sistem
Raw water is treated in a water treatment
plant
Filtration
Separates leaves , rubbish and fish
Oxidation
Removes unpleasent smell and taste
Coagulation
Alum coagulates suspended particles ,
whereas slaked lime neutralise the acidity
of alum
Sedimentation
Allows the lump of impurities to settle at
the bottom for removal
Filtration
Removes remaining suspended particles ,
algae , bacteria and some chemicals
through sand filters
Chlorination
Chlorine kills harmful microorganisms and
decolourises the water
Fluoridation
A fluoride compound is added to prevent
dental decay
Water pollution
Domestic wastes
Effects : Reduction of oxygen level in
water , Water becomes smelly
Ways : Upgrading sewerage and sanitary
systems , Aerating the water to get rid of
unpleasant smells
Industrial wastes
Rashes , Cancer
Treating chemical wastes before disposal ,
Enforcing laws
Agricultural wastes
Algal bloom kills aquatic life due to the lack
of oxygen in water , Increased population
of bacteria in water
Using biodegradable fertilisers , Using
biological methods to kill pests
Oil spills
Kills marine life , Ruins beautiful beaches
Improving air surveillance by Air Police
Unit , Using bioremediation method to clean
up oil
Siltation
Flash floods , Water becomes cloudy
Controlling deforestation , Deepening and
widening rivers
What are the ways to preserve the
sustainability of water ?
Using eco-friendly products
Treating sewage water
Conserving water
Reusing rainwater
Controlling pollution of rivers
To ensure the sustainability of water for
future generations