2. Water is the most abundant substance on
earth.
Like any other substances, water has its own
unique characteristics.
3. A. Physical Characteristics of Water
1. Water can exist in three states:
a. Solid b. Liquid c. Gas
5.1 Physical Characteristics of Water
4. 2. At room temperature, pure water is a
a. colourless,
b. odourless and
c. tasteless.
5.1 Physical Characteristics of Water
5. liquid solid
Freezing point of water is the temperature at
which water freezes into ice.
5.1 Physical Characteristics of Water
Freezing Point of Water
1.Water changes from liquid to solid at its freezing
point.
6. 2. The freezing point of pure water is 0 oC.
3. The temperature remains constant at 0 oC until water
freezes completely.
5.1 Physical Characteristics of Water
7. 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!
5.1 Physical Characteristics of Water
8. liquid gases
Boiling point of water is the temperature at
which water boils and becomes steam.
5.1 Physical Characteristics of Water
Boiling Point of Water
1. Water boils at its boiling point.
9. 2. The boiling point of pure water is 100 oC.
3. The temperature remains constant at 100 oC until
water boils completely.
5.1 Physical Characteristics of Water
10. 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!
5.1 Physical Characteristics of Water
11. 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.
5.1 Physical Characteristics of Water
12. 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.
5.1 Physical Characteristics of Water
14. Hydrogen Oxygen
5.2 Composition of Water
Composition of Water
1. Water is a compound. It is made of two different
elements.
Water
15. 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
5.2 Composition of Water
16. Hydrogen is
released at the
cathode
Oxygen is
released at the
anode
5.2 Composition of Water
3. The volume of hydrogen released is always
twice the volume of oxygen released.
17. Hydrogen atoms
Each water molecule consists of one atom of oxygen and
two atoms of hydrogen.
5.2 Composition of Water
Water is made up of one part of oxygen and two parts of
hydrogen.
Oxygen atom
4.
18. 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
5.2 Composition of Water
19. 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
21. 1. What is a solution?
• A solute is the
substance that dissolves.
• A solvent is the
substance that the solute
dissolves in.
5.4 Solution and Solubility
22. 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
5.4 Solution and Solubility
2. Depending on the amount of solutes in
solutions, there are three types of solutions.
Solution
23. 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
5.4 Solution and Solubility
24. 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.
5.4 Solution and Solubility
25. 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
5.4 Solution and Solubility
26. 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.
5.4 Solution and Solubility
27. 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.
5.4 Solution and Solubility
28. 1. What are the factors affecting the rate
of dissolving a solute?
a. Temperature
b. Rate of stirring
c. Size of solute particles
5.4 Solution and Solubility
29. 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.
5.4 Solution and Solubility
30. 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.
5.4 Solution and Solubility
31. 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.
5.4 Solution and Solubility
32. 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.
5.4 Solution and Solubility
33. 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.
5.4 Solution and Solubility
34. • Alcohol • Turpentine • Acetone
5.4 Solution and Solubility
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:
35. 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
5.4 Solution and Solubility
36. 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).
5.4 Solution and Solubility
37. 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
39. 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
40. 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
41. 1.
2.
An alkalis is hydroxide or metal oxide that
dissolves in water.
Example: potassium hydroxide, sodium
hydroxide, calcium hydroxide, ammonium
hydroxide solutions.
43. 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
44. 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
45. a. Most pure
b. Has very little dissolved substances and a
little dust
46. a. Not clean
b. Has a lot of dissolved substances and dirt
such as microorganisms and silt
48. a. Has the most substances of salt
b. Has the most of dirt.
49. 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
54. 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.
56. 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.
57. c. Boiling and
chlorination
Only kills
microorganisms in
water
Water is free from
dangerous
microorganisms
Water still has
dissolved
substances and
suspended
substances.
58. 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.
