1.3 Water hardness

• Physical properties of water: taste, colour, odour and boiling point
• Hard and soft water
• Methods of softening temporary hard water: boiling, addition of washing soda, distilling
• Advantages and disadvantages of hard water and soft water

• describe the physical properties of water
• distinguish between hard and soft water in nature
• apply methods of softening hard water in day-to-day life
• outline the advantages and disadvantages of hard and soft water
• appreciate the applications of soft and hard water in day-to-day life

“What is the importance of different types of water?”

“Why is hard water preferred for drinking?”

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1. The physical properties of water
   40 min · 1 practice tasks · quiz
   Colour, odour and boiling point can all be checked without tasting anything.
2. Water from different sources
   40 min · 1 practice tasks · quiz
   Water that has travelled through rock has dissolved minerals from it; rain has not.
3. The soap test
   40 min · 1 practice tasks · quiz
   Same soap, same shaking: lather means soft, scum means hard.
4. Hard and soft water
   40 min · 1 practice tasks · quiz
   Hardness is dissolved calcium and magnesium, not dirt.
5. What causes hardness
   40 min · 1 practice tasks · quiz
   Soft rain, soluble rock and time. Take away any one and the water stays soft.
6. Temporary and permanent hardness
   40 min · 1 practice tasks · quiz
   One kind yields to boiling; the other does not.
7. Softening by boiling
   40 min · 1 practice tasks · quiz
   The cheapest method, and it moves the calcium from the water to the kettle.
8. Softening with washing soda
   40 min · 1 practice tasks · quiz
   Sodium carbonate removes both kinds of hardness, costs no fuel, and saves soap.
9. Softening by distillation
   40 min · 1 practice tasks · quiz
   Only the water evaporates, so everything dissolved in it is left behind.
10. Comparing the softening methods
    40 min · 1 practice tasks · quiz
    Three methods, three costs; the job decides which one you use.
11. Advantages of hard water
    40 min · 1 practice tasks · quiz
    The calcium that ruins a wash is the same calcium a growing body needs.
12. Disadvantages of hard water
    40 min · 1 practice tasks · quiz
    Wasted soap, scum on clothes and scale in pipes: the costs fall on households and industry alike.
13. Advantages and disadvantages of soft water
    40 min · 1 practice tasks · quiz
    Soft water is better for washing and worse for drinking. Neither kind wins outright.
14. Choosing the right water for the job
    40 min · 1 practice tasks · quiz
    One tap can serve every job. What changes is whether the water is softened first.