Air and water notes

WATER

•      Like air, water is also essential for life.

•      Water is the only substance on Earth that is in liquid form at the temperatures commonly found on the surface of our planet.

Figure 6: Water is in liquid state on the surface of the Earth

•      Water is a universal solvent, i.e. most of the substances can be easily dissolved into it.

•      This allows water to carry nutrients to cells, and carry waste away from them.

•      In addition to this, water has the unique property of expanding as it freezes.

REMOVING IMPURITIES FROM WATER

•      Water purification is the process of removing undesirable chemicals, biological contaminants, and suspended solids from contaminated water.

•      Water is purified for human consumption (drinking water) but water purification may also be designed for a variety of other purposes.

Removing Insoluble Impurities:

•      Insoluble impurities such as sand can be separated by:

Sedimentation:

•      Sedimentation is a physical water treatment process used to settle out suspended solids in water under the influence of gravity.

CITY WATER SUPPLY

•      To make water from lakes and rivers fit for drinking, it is purified in big purification plants before it is made available to homes.

Figure 14: Water supply system in city

•      The city water supply system includes all the processes.