20 essential facts about the various man made materials

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1. A mixture of clay and limestone is heated in a kiln to make cement.

2. Concrete is made by mixing cement, sand, gravel and water.

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3. Steel rods or steel mesh embedded in wet concrete is called reinforced concrete cement.

4. Glass is made by mixing sand, soda ash and limestone.

5. Different kinds of glass are made by adding different chemicals and by controlling the way molten glass is cooled.

6. Moulded clay is fired to get ceramic.

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7. Plastics are polymers (chain of monomers).

8. Thermoplastic articles become soft when heated and harden when cooled.

9. Thermosetting plastics take a permanent shape when heat and pressure are applied.

10. Synthetic fibres are made by squirting certain liquids through tiny holes in a metal plate called spinnerets.

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11. Rayon is made from cellulose obtained from wood pulp.

12. Nylon and polyester are made from chemicals.

13. Soap is made by reacting sodium hydroxide with animal or vegetable fats. Its molecule has two ends; the tail end of the soap molecule is oil soluble and tends to dissolve in the oily covering of dirt particles and the other end is water soluble.

14. Detergents are derived from petroleum and other sources. They are similar to soaps in their structure. They are unaffected by hard water.

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15. Nitrogen, phosphorus and potassium are major elements needed for proper growth of plans. Man-made chemicals which provide plants with these elements are called fertilizers.

16. Pesticides kill pests. They can be insecticides, herbicides or fungicides.

17. Drugs are substances used to cure or prevent diseases or to ease pain.

18. Cosmetics improve our appearance.

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19. Dyes are mostly complex organic compounds. Coal tar is the raw material of most dyes.

20. Pigments are used in making and printing inks.

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