Page 78 - ICSE Chemistry 6

Activity 4.3

Aim: To study the presence of dissolved impuri es in natural water
Materials required: 2 China dishes, some rainwater, some sea water
Procedure

• Take samples of rainwater and sea water in separate China dishes.
• Keep the China dishes in sun. Allow the water to evaporate.
Observa on: The amount of residue in rainwater is negligible and maximum in case of sea water.

Conclusion: This shows that amount of dissolved impuri es vary from source to source.

Sources of Water

Rainwater Surface water Groundwater

• Important part of the • Water collected under the
water cycle Oceans and Rivers, lakes, streams ground
• Purest form of water seas and ponds • Water containing
• Replenishes other sources dissolved salts and free
of water • Saline water Water containing from suspended par cles
• Unfi t for drinking, dissolved salts and • Found in wells and springs
washing, irriga on suspended impuri es • Drawn by handpumps,
and agricultural tube wells or bore wells
prac ces

STATES OF WATER

Water exists in all three states of ma er—solid, liquid and gas.
In solid state, water exists as snow or frost. This happens on cooling water. When snow gets compact, it
forms ice.
In liquid state, water exists as a free-fl owing liquid. This happens at room temperature.
In gaseous state, water exists as water vapour or steam. This happens on boiling water.
The molecules of ice, water and steam are exactly the same. The three states of water can be interchanged
by changing the temperature as follows.

Ice Hea ng Water Hea ng Steam or water vapour
(0°C or less) Cooling (Room temperature) Cooling (100°C or more)

Water Cycle
The con nuous circula on of water from the earth to the atmosphere and back again to the earth is
called water cycle.

Water in various water bodies such as oceans, seas, rivers, lakes, ponds and streams evaporates due to
heat of the sun and forms water vapour. A large amount of water is also given out by the leaves of plants
during transpira on.

64