Slides about the evaporation of water - process - factors affecting rate of evaporation - application in daily life

1. Evaporation
of Water
Chapter 5 : Water and Solution
KSSM Science
Form 2

2. • Evaporation of water is the
process that happens at the
surface of water that
changes water to water
vapour.
• This process occurs at any
temperature.

3. Why molecules of water
can evaporate?
• The molecules of
water at the surface
have higher kinetic
energy
• The molecules of
water can move faster
and escape into the air.
Process of
evaporation of
water

4. •When you hang a wet
clothes under the hot
sun, the water
evaporate, leaving the
clothes to dry
•This is evaporation

5. FACTORS AFFECTING RATE OF
EVAPORATION:
HOW FAST WATER CAN EVAPORATE?
There are four factors affecting
the rate of evaporation of water
• humidity
• surrounding temperature
• exposed surface area of water
• movement of air

6. FACTOR: HUMIDITY
• Dry air contains less water vapour.
• So, dry air can hold more water molecules that escape from the surface of
water.
• Thus, the rate of evaporation of water increases.
• Dry air (like in a desert)  less water vapour  low humidity  rate of
evaporation increase (water evaporate faster)
• Humid air (like after raining) high water vapour  high humidity  rate of
evaporation decrease (water evaporate slower)

7. FACTOR: SURROUNDING
TEMPERATURE
• When the surrounding
temperature increases,
• the water molecules at the
surface gain more energy,
• water molecules move faster
and escape into the air easily
• Thus, the rate of evaporation
of water increases.

8. FACTOR: EXPOSED
SURFACE AREA OF
WATER
• Exposed surface area of
water that is larger
allows more water
molecules to escape
• thus increasing the rate
of evaporation of
water.
• the larger the surface
area, the faster water
molecules evaporate
Which of these cloth will dry faster?
A?
B?
C?
D?
E?
A B C D E

9. FACTOR: MOVEMENT
OF AIR
• Movement of air sweeps
away water vapour in
the air.
• High speed of wind
causes the air at the
surface of water to dry
• This increases the rate of
evaporation of water.
Eh!!

10. Applications of
Evaporation of
Water in Daily Life
• Clothes hung on clothes lines
have large exposed surface
areas. So, the clothes will dry
faster.
• Hair dryer that blows
hot air increases the
temperature, thus
increasing
evaporation of water
(from wet hair)

11. Applications of Evaporation
of Water in Daily Life
Sea salt is obtained from the evaporation
of seawater.
Seafood that is dried can be kept longer
as microorganisms cannot survive
without water.

12. NOTE!
•Please read additional information
about evaporation from any reference
books and internet