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

Physics: Lesson 19/ Ch 17: Water-A life Giving Liquid

Objectives

• Differentiate Hard and soft water

• Discuss the causes of Scarcity of Water

• Enumerate ways on how to conserve water.

HARD WATER AND SOFT WATER

Is water from all sources is same? What type of water do you have in your home?

• What is Hard water?

• What is soft water?

What type of water is rainwater? What happens if we wash our clothes using rainwater?

• Hard water?

• Soft Water?

SOFT WATER - is a water that lathers with soap

• 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.

HARD WATER- water that has not lather with soap

• 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

How to test soft and hard water

• see video

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

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Hardness of Water-Causes and Removal

• CAUSE

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

• 2 types of hardness (Temporary and Permanent)

1. Temporary Hardness- It is caused by the presence of bicarbonate of calcium and magnesium salts

-IT can be easily removed by boiling.

2.Permanent Hardness

• 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.

Multiple Choice

A rainwater is an example of what type of water?

• soft

• hard

• semi-hard

• very hard

Multiple Choice

__________ hardness is caused by bicarbonates of calcium and magnesium salt

• permanent

• temporary

Multiple Choice

________ hardness is caused by chlorides and sulphates of calcium and magnesium

• temporary

• permanent

Multiple Select

What are disadvantages of using hard water?

• not suitable fir washing clothes

• its not good choice for boiler

• not suitable for dyeing and photography

• it easily lathers with soap

CAUSES SCARCITY OF WATER

• Population Growth

• Wastage

• Over exploitation of ground water

• Urbanisation and Industrialisation

• Global Warming

• Deforestation

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Multiple Choice

it is one of the causes of water scarcity in which forest are cut at an alarming rate which results in decrease in the rain.

• wastage

• deforestation

• population growth

• urbanisation

Multiple Choice

Another cause of scarcity of water due to improper use of water by leaving the tap open when no one uses it.

• deforestation

• wastage

• industrialisation

• population growth

Multiple Choice

Is is another cause of water scarcity due to so many users it increases the demand of water supply is known as____

• wastage

• global warming

• population growth

• overexploitation

Multiple Choice

______ is a cause of water scarcity due to setting up of new factories and industries increased the demand of water.

• wastage

• population growth

• deforestation

• industrialization

Multiple Choice

_____ is a cause of water scarcity due to increase of global temperature causes changes in the seasons which leads to decrease of rain that falls over the earth.

• population growth

• wastage

• deforestation

• global warming

WATER CONSERVATION

• 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

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