Points to Remember, Glossary, Concept Map

Points to Remember

• Next to air, water is the most important resource for our survival.

• Water contains hydrogen and oxygen as its constituent elements. Its molecular formula is H₂O.

• Water is broken down into its constituent elements by electrolysis. During electrolysis hydrogen and oxygen are obtained in the ratio 2:1

• Water has a maximum density of 1 g/cc at 4°C. At temperatures below and above 4°C, water has a density of less than 1 g/cc. This unique property of water helps in the survival of aquatic life in winters and summers.

• Sea water contains many minerals and salts dissolved in it and so it is said to be saline.

• Water freezes at 0°C and boils at 100°C.

• Water is a universal solvent as it can dissolve many substances.

• Water that is used for drinking is called potable water.

• Water has dissolved gases which are used by aquatic life for respiration and photosynthesis.

• Hardness of water is due to the presence of dissolved salts of calcium and magnesium.

• Water pollution is the result of dumping untreated domestic solid waste and sewage, agricultural waste, industrial effluents into lakes, rivers, etc.

GLOSSARY

1. Electrolysis Breaking down of substances by the passage of electric current.

2. Potable water Water used for drinking.

3. Saline water Water containing sodium chloride (common salt).

4. Sterilization Addition of chemicals to kill the microorganisms present in water.

5. Eutrophication Over growth of algae in water bodies due to excessive fertilizers.

6. Specific heat Amount of heat that is needed to raise the temperature of a unit mass of

7. capacity a substance by 1°C.

8. Latent heat of fusion Amount of heat energy required by ice to change into water.

9. Aeration The process in which air under pressure is blown into filtered water.

10. Water pollution Addition of unwanted waste materials to the water.

11. Domestic sewage Wastewater that is disposed of from households.

12. Water conservation Saving water for the use in future.

Concept Map

REFERENCE BOOKS

1. Water science fair projects – Madeline Goodstein.

2. Basic chemistry – Karen C. Timberlake & William Timberlake.

3. Chemistry of water treatment – Samuel D. Faust Osman M.Aly.

 4. Textbook of Environmental Chemistry – Balarampani.

INTERNET RESOURCES

1. http://www. youtube . com/watch?v= bZHymnnrSzc

2. http://www.un.org/cyberschoolbus/ waterquiz/waterquiz4/index.asp

3. http : / / w w w. e x pl ai nt hat stu f f . c om / waterpollution.html