Sience

1. Chapter 5: water and
solution
Index 5.1 physical characteristic of water

2. Learning outcome
By the end of the lesson, student are able to:
1. list the physical characteristic of pure water
2. Write the definition of surface tension and capillary action
3. write the effect of absorption and release of heat on the state of water
4. list factor affecting the rate evaporation of water

3. Physical characteristic of water
•Water is basic need of all life in earth
Boiling point = 100ͦc
Freezing point = 0 ͦC
Density = 1 gcm-3
You need to remember all
this three value

4. Physical
characteristic
of pure
water
colorless
odorless tasteless
Liquid at room
temperature
High surface
tension
Adhesive and
cohesive
force

5. Cohesive force and adhesive force
•Cohesive force is attraction of water molecule to each other
•Adhesive force is attraction of water molecule to other molecule or surface
•Allow capillary action in xylem tube
•Capillary action is process that water
is being transport from the roots to
the leaves of plants.
Adhesive force which
attraction between
water molecule and
cell wall
Cohesive force
which attraction
between same
water molecule

6. High surface tension
•Surface tension is occur because of cohesive force which is
attraction or interaction between same water molecule at the
surface.
•Insect able to walk on surface of water
due to high surface tension.

7. Absorption and release of heat to state of water
Blue arrow show heat is
release
Red arrow show heat is
absorbed

8. Composition of water
• Water is compound that made up of two hydrogen atom and one
oxygen atom
• Chemical symbol for water is H2O

9. ELECTROLYSIS OF WATER
 Electrolysis is method used to
determine the composition of
element in water molecule.
 It shown that oxygen gas release at
anode while hydrogen gas release at
cathode
ANODE CATHODE
 Anode is electrode that connect to
positive terminal of battery
 Cathode is electrode that connect to
negative terminal of battery

10. Effectof impuritieson melting andboiling pointof water
The freezing point and melting point of pure water is 0°C while the boiling of pure
water is 100°C.
pure water or distilled water do not contain any dissolve substances
 When impurities like common salt (sodium chloride) is added into the pure water,
the boiling point of the impure water will be higher than 100°C and its freezing point
or melting point will be lower than 0°C (Impure water is water contains dissolve
substances)
Impurities (salt) lower the
melting point
and higher the boiling
point

11. Evaporation of water
• Evaporation is process where water is changes into water vapour which happen at surface of water and occur at
any temperature.
The molecule of water at surface
have high kinetic energy, they
become energetic (move faster)
and escape into the air

12. Factor that affecting the rate of evaporation of water

13. Humidity
• Humidity is water vapour
contain in the air.
• Dry air can hold more water
molecule escape from surface
of water
• When dry air (low humidity) ,
rate of evaporation increase
Surrounding temperature
• Increase in surrounding
temperature, increase rate of
evaporation
• water molecule at surface gains
more energy, move faster and
easy escape into air
Exposed surface area of water
• Large surface area, rate of
evaporation increase
• Allow more water molecule
to escape
Movement of air
• High speed of wind, increase
rate of evaporation
• Sweep away water vapour in
the air which cause air at
water surface to dry