Chapter5 water and solution FORM 2

HAPPY
Chapter 5
Water and Solution

Water is the most abundant substance on
earth.
Like any other substances, water has its own
unique characteristics.

A. Physical Characteristics of Water
1. Water can exist in three states:
a. Solid b. Liquid c. Gas
5.1 Physical Characteristics of Water

Physical characteristics of water
PURE WATER IS COLOURLESS,
ODOURLESS, TASTELESS
LIQUID

liquid solid
Freezing point of water is the temperature at
which water freezes into ice.
Freezing Point of Water
1.Water changes from liquid to solid at its freezing
point.

When the temperature drops, the water
particles move slower.
Therefore, the forces of attraction among the
particles grow stronger.
At 0 oC, the forces of attraction are so great
that the water particles are held in fixed
positions.
Waterfreezes into ice!

2. The freezing point of pure water is 0 oC.
3. The temperature remains constant at 0 oC until water
freezes completely.

liquid gases
Boiling point of water is the temperature at
which water boils and becomes steam.
Boiling Point of Water
1. Water boils at its boiling point.

2. The boiling point of pure water is 100 oC.
3. The temperature remains constant at 100 oC until
water boils completely.

When the temperature rises, the water particles
move faster and further apart.
Therefore, the forces of attraction among the
particles grow weaker.
At 100 oC, water particles move so fast that
they overcome the forces of attraction and
leave the liquid’s surface.
Waterbecomessteam!

5. Water conducts heat slowly. Water is a poor
thermal conductor.
6. Water is also a poor electrical conductor.
7. The density of water varies with temperature.
Pure water has the maximum density of 1 g
per cm3 at 4 oC.

B. Effects of Impurities on the Physical
Characteristics of Water
1. Impurities in water can change the
physical characteristics of water. Sometimes
the change is noticeable and sometimes it is not.

Physical
characteristic
Example
Taste Purewateristastelessbutseawaterissalty.
Odour Purewaterisodourless.Waterwithdecayedmatterhasanunpleasant
smell.
Colour Purewateriscolourlessbutmuddywaterisbrownishincolour.
Density Purewaterislessdensethanseawater.
Electricalconductivity Purewaterwithafewdropsofsulphuricacidcanconductelectricity.
Freezingpoint o
Purewaterfreezesat0Cbutseawaterfreezesatalower
temperature.
Boilingpoint o
Purewaterboilsat100Cbutseawaterboilsatahighertemperature.
2. Here are some examples:

Hydrogen Oxygen
5.2 Composition of Water
Composition of Water
1. Water is a compound. It is made of two different
elements.
Water

2. Water can be broken down to its elements
through electrolysis.
A method to break down a compound by passing
an electric current through its liquid or solution

Hydrogen is
released at the
cathode
Oxygen is
released at the
anode
3. The volume of hydrogen released is always
twice the volume of oxygen released.

Hydrogen atoms
Each water molecule consists of one atom of oxygen and
two atoms of hydrogen.
Water is made up of one part of oxygen and two parts of
hydrogen.
Oxygen atom
4.

5. Therefore, scientists represent water with the
following formula:
H2O
H – Represents the hydrogen atom
2 – Shows that there are two atoms of hydrogen
O – Represents the oxygen atom

Applying the principle of water evaporation
In our daily life.
1. To drying clothes
2. To drying hair
3. To drying agricultural produce
4. To drying fish and prawn
5. To cooling the body
6. To producing the common salt

EVAPORATION BOILING
SIMILARITIES Liquid gas
Absorps heat
DIFFERENCES Occurs at any temperature Occurs only at boiling point
Occurs only on the exposed
surface of a liquid
Occurs throughout the liquid
No bubbles are formed Bubbles formed throughout the
liquid
Absorbs heat from the
surroundings when water
turns into gas
Requires heat supplied by a source
such as a lighted bunsen burner

Solution and Solubility
5.4 Solution and Solubility
solution
Solution and suspension
Factors affecting solubility
Rate of dissolving
Water as solvent
Organic solvents

1. What is a solution?
• A solute is the
substance that dissolves.
• A solvent is the
substance that the solute
dissolves in.

Dilute solution
Contains a little
dissolved solute
Can dissolve a lot
more solute
Concentrated solution
Contains a lot of
dissolved solute
Can dissolve a little bit
more solute
Saturated solution
Contains the maximum
amount of dissolved solute
Cannot dissolve any more
solute
All these solutions have a clear appearance
2. Depending on the amount of solutes in
solutions, there are three types of solutions.
Solution

1. What is a suspension?
A suspension is a mixture containing insoluble
substances.
2. There are many suspensions around us.
Muddy water, fruit juices, chocolate drink, blood

1. What is ‘solubility’?
The solubility of a solute is the maximum amount of solute in
grams that will dissolve in 100 g of solvent at a given
temperature.
For example, the solubility of sodium chloride is 38 g per 100
g of water at 20 oC.
This means that you can dissolve not more than 38 g of sodium
chloride in 100 g of water at 20 oC.

2. Factors Affecting the Solubility of a Solute
a. The nature of the solvent
b. The nature of the solute
c. The temperature of the solvent

i. The nature of the solvent
- The solubility of a solute differs in
different solvents.
Example:
Only a little iodine can dissolve in water. Iodine can
dissolve very well in alcohol.

ii. The nature of the solute
Different solutes have different solubility
in the same solvent.
Example:
At the same temperature, sodium chloride has a
lower solubility in water compared to copper chloride.

1. What are the factors affecting the rate
of dissolving a solute?
a. Temperature
TEMPERATURE
RATE OF STIRING
SIZE OF SOLUTE PARTICLES

i. Temperature
The higher the temperature of the solvent, the higher the
rate of dissolving.
:
We use hot water to make
tea. One reason for this is
that hot water increases
the rate of dissolving of
certain substances in the
tea leaves.

ii. Rate of stirring
The higher the rate of stirring, the higher the rate of
dissolving.
:
The faster you stir the
soup, the faster the salt
dissolves in it.

iii. Size of solute particles
The smaller the size of the solute particles, the higher the
rate of dissolving.
Smaller pieces of palm
sugar can dissolve in water
faster than a big piece of
it.

Water is a good solvent. Almost everything can dissolve in it to
produce solutions. Therefore, water is also known as the
universal solvent.
Water acts as a medium in many chemical reactions in
our body.
Water dissolves and transports many substances in our
body such as digested food and waste products.
Water dissolves cleaning agents such as soap powder,
dishwasher liquid and toilet cleaner.

Water dissolves various substances. This enables us to
use water in cooking and making drinks.
Water is used extensively in food industry as a solvent.
Water is used to prepare traditional and modern liquid
medicines.
Farmers use water to dissolve pesticides.
Water is needed in plants to transport food and
dissolved minerals.

• Alcohol • Turpentine • Acetone
Some substances cannot dissolve in water but they can
dissolve in organic solvents.
What are organic solvents?
Organic solvents are carbon compounds that are used
as solvents.
Examples:

1. We use many organic solvents in various products.
To produce lacquers and varnishes
Alcohol
Turpentine
Acetone
To produce various types of ink
To prepare iodine solution (as an antiseptic)
To produce perfume
To produce paints
To remove paint stains
To produce nail polish
To remove nail polish

2. Organic solvents are very useful to us.
a. They are volatile. Therefore, products such as
paints, lacquers, varnishes and inks become dry in a
short period of time.
b. They can dissolve many solutes that do not dissolve
in water.
3. However, products containing organic solvents
should be handled carefully.
a. They are flammable and should be stored away
from heat.
b. They are toxic and carcinogenic (likely to cause
cancer).
Solution
and
solubility

1.
2.
An acid is a substance that has a hydrogen
atom, which can be replaced by a metal
or ammonium.
Acid can be divided into two groups and
differences are shown below

ACID
Organic acid
Example
Acetic acid
Formic acid
Lactic acid
Malic acid
Citric acid
Tannic acid
Tartaric acid
Inorganic acid
Example
Sulphuric acid
Nitric acid
Hydrochloric acid
Carbonic acid

3.An acid exist in three state which are
a. solid – tartaric acid
b. liquid – ethanoic acid
c. gas – hydrogen chloric
4. The properties of acids
a. Taste sour
b. Are corrosive
c. Change blue litmus paper to red
d. Have pH values of less than 7
e. React with carbonates to release carbon dioxide
and form salt and water
acid + cabonates salt + water + carbon dioxide

f. React with active metals to release hydrogen and form
salt.
g. React with alkalis to form salt and water
acid + metal salt + hydrogen
acid + alkali salt + water

1.
2.
An alkalis is hydroxide or metal oxide that
dissolves in water.
Example: potassium hydroxide, sodium
hydroxide, calcium hydroxide, ammonium
hydroxide solutions.

1 2 3 4 5 6 7 8 9 10 11 12 13 14
neutral
Acidity increases Alkalinity increases

acid + alkali  salt water+
Note:
Neutralisation
Neutralization is a process where
Where acid reacts with alkali, salt and water are formed.
Different kinds of acids and alkalis will form different types of salt.
5.5 Acid and Alkali

Natural Sources of Water
Natural Sources of Water
From Ocean
• Salty
• Not suitable for
human consumption
From lakes, streams,
rivers, ground water
(well) and rain
• Fresh Water
• But not pure, need to be purified
5.6 Water Purification

a. Most pure
b. Has very little dissolved substances and a
little dust

a. Not clean
b. Has a lot of dissolved substances and dirt
such as microorganisms and silt

a. Has microorganisms and dissolved
substances
b. Cleaner than river

a. Has the most substances of salt
b. Has the most of dirt.

Usage of Water
Usage of Water
Domestic Use
of Water
• Drinking
• Washing
• Watering
Plants
Agricultural Use
of Water
• Irrigation
• Aquaculture •
•
•
Direct Use of
Rivers and
Streams
Generate
Hydroelectric
Power
Recreation
Transportation
Industrial Use
of Water
• Cooling
• Washing
• Disposal
of Waste
5.7 Water Supply System

Chlorine solution
METHOD OF PURIFICATION
Chlorination

Filtration
Muddy water
Fine sand
Coarse sand
Pebbles
Gravel
filtrate

Distillation
Muddy
Water
Water
out
Water in
Liebig
condenser
Distilled
water

1. Water from natural sources have various
impurities such as microorganisms, dissolved gases,
mineral salts and silt.
2. Water from natural sources must be purified so that it
save to drink and use.
3. Table shows the advantage and disadvantage of
water purification.

Waterpurificationmethod advantage disadvantage
a. Filtration
Onlyremoves
impuritiesthatare
coarsesuchas
suspendedsubstances.
Sandfiltersare
commonlyused
Waterisclear
andfree
suspended
particlesonly
Waterstillhas
microorganisms
anddissolved
substances
(suchas
mineralsalts)

b. Distillation
 Prepares pure or
distilled water
 Water is free
from all
suspended
substances,
microorganisms
and dissolved
substances.

Water does
not make
good
drinking
because it
does not
contain
dissolved
mineral
with our
body need.

c. Boiling and

chlorination
Only kills
microorganisms in
water
 Water is free from
dangerous
microorganisms
 Water still has
dissolved
substances and
suspended
substances.

WATER TREATMENT PLANT
1. Refer to your text book pg. 36 and draw figure 5.34
PRESERVATION OF WATER QUALITY
1. Find out the ways to control water pollution on page 41.

Chapter5 water and solution FORM 2

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Chapter5 water and solution FORM 2