Physics: Lesson 29/ Ch 17: Water-A life Giving Liquid

What is Hard water?

What is soft water?

Hard water?

Soft Water?

Soft water is surface water that contains low concentrations of ions and in particular is low in ions of calcium and magnesium.

Therefore, rainwater that easily bubbles produced by soap is a soft water.

It has a large concentration of minerals, such as calcium and magnesium

Hard water is not suitable for washing clothes, as it does not lather well

Its not good for dyeing & photography as it causes changes of colors used.

Its not good for boilers because it will corrodes metals

see video

https://www.youtube.com/watch?v=bBYsfEHKYCk&t=72s

CAUSE

Generally contains dissolved salts such as chlorides, sulphates and bicarbonates of calcium and magnesium.

2 types of hardness (Temporary and Permanent)

It is caused by the presence of chlorides and sulphates of calcium and magnesium

This cannot be removed by boiling alone.

It can be removed by treating the water with washing soda(sodium carbonate).

By boiling hard water with washing soda the chlorides and sulphates of Ca & Mg get converted to NaCl and sodium sulphate and the insoluble precipitates are filtrated.

Population Growth

Wastage

Over exploitation of ground water

Urbanisation and Industrialisation

Global Warming

Deforestation

Repair a leaking tap immediately

Dams and reservoirs should be constructed to collect water and controls floods.

Farmers should use better methods of irrigation

Water from industries whould be recycled

More and more trees should be planted

Rainwater should be harvested