for class vii standard.

2. CHAPTER # 3
WATER

3. 3.2.3 Recognize the boiling and freezing point of
water
3.3: TYPES OF WATER
3.3.1 Define soft water
3.3.2 Describe hard water
3.2: PROPERTIES OF WATER

4. At the end of the class you all will be able to:
• boiling and freezing point of water
• soft water
• hard water

5. Liquids have a characteristic
temperature at which they
turn into solids, known as
their freezing point.
When a liquid is heated, it
eventually reaches a
temperature at which the vapor
pressure is large enough that
bubbles form inside the body of
the liquid. This temperature is
called the boiling point.

6. The
normal boiling
point of water is
100oC ( 373.15 K,
213°F)
Freezing point for water
is0°C (273.15 K, 32°F ).

7. Soft water:
The water which gives lather with
soap water is called soft water. It contains
lower concentrations of minerals such as
calcium and magnesium. It contains sodium
ions. Example of soft water is rainwater and
distilled water.

8. HARD WATER:
Hard water does not form lather
with soap easily, but it has a
pleasant taste and is good for the
bones and teeth, as it contains
dissolved calcium compounds.
There are two types of hardness:
• Temporary hardness
• Permanent hardness

9. • Hard water is unfit for washing as it is difficult to
form lather with soap.
• Scum may form in a reaction with soap, wasting
the soap.
• Furring of tea kettles will take place due to the
formation of carbonates of calcium and
magnesium.
• Hard water blocks hot water pipes.
Disadvantages of hard water