Compounds
A compound is a substance made up of two or more elements chemically combined in a fixed proportion by mass. For example, water () is a compound made up of two elements, hydrogen and oxygen, chemically combined in a fixed proportion of 1 : 8 by mass (Atomic masses: H = 1 u, O = 16 u, so H2 : O = 2 u : 16 u or 1 : 8). Similarly, common salt (sodium chloride, NaCl) is a compound made up of two elements, sodium and chlorine; ammonium chloride () is a compound made up of three elements,nitrogen, hydrogen and chlorine; sand (silicon dioxide, ) is a compound of silicon and oxygen, and marble (calcium carbonate, ) is a compound made up of calcium, carbon and oxygen elements.
Some more examples of compounds are : Ammonia (), Carbon dioxide (), Ice (), Steam (),Chalk (Calcium carbonate, ), Limestone (Calcium carbonate, ), Lime or Quicklime (Calcium oxide, ), Slaked lime [Calcium hydroxide, ], Methane (), Glucose (), Sugar or Canesugar (), Starch [(], Baking soda (Sodium hydrogencarbonate, ), Washing soda (Sodium carbonate, ), Potassium nitrate (KN03), Potassium sulphate (), Sodium sulphate (), Copper sulphate (), Iron sulphide (), Hydrochloric acid (HC1), Sulphuric acid (),Nitric acid (), Hydrogen bromide () and Sodium hydroxide (). We have given the formulae of all these compounds so that you may be able to write the names of the elements present in them.Compounds can be further divided into three classes : acids, bases and salts, on the basis of their properties. For example, sulphuric acid is an acid, sodium hydroxide is a base whereas sodium sulphate is a salt. We will now take one example to understand the characteristic properties of a compound.
Notes
Matter in Our Surroundings - Notes
1. 3. Non-Metals are Bad Conductors of Heat and Electricity.
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3. The Case of a Liquid Solute Dissolved in a Liquid Solvent
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4. 11. Metals Usually Have a Silver or Grey Colour
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8. To Study the Properties of a Colloid
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9. 7. Metals are Solids at the Room Temperature
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10. 7. Non-Metals may be Solid, Liquid or Gases at the Room Temperature.
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11. Separation Of Mixture Of a Solid And a Liquids
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12. 6. Non-Metals are Not Strong. They Have Low Tensile Strength.
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17. 11. Non-Metals Have Many Different Colours.
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18. To Study the Properties of a Compound of Iron and Sulphur
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19. 1. Separation by a Suitable Solvent
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27. 6. Metals are Usually Strong. They Have High Tensile Strength.
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28. To Study the Properties of a Solution
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34. Separation of Mixture Of Two Solids
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39. 3. Metals are Good Conductors of Heat and Electricity.
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40. Chemical Formula for daily use material
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43. Solutions, Suspensions And Colloids
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46. To Distinguish a Colloid from a Solution
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48. To Separate a Mixture of Alcohol and Water
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49. To Study the Properties of a Suspension
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