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.
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Matter in Our Surroundings - Notes
2. 7. Metals are Solids at the Room Temperature
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4. 3. Non-Metals are Bad Conductors of Heat and Electricity.
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8. 7. Non-Metals may be Solid, Liquid or Gases at the Room Temperature.
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9. 11. Non-Metals Have Many Different Colours.
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15. 8. Metals Generally Have High Melting Points and Boiling Points.
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19. 8. Non-Metals Have Comparatively Low Melting Points and Boiling Points
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23. To Study the Properties of a Suspension
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24. Effect of Temperature and Pressure on Solubility
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25. Chemical Formula for daily use material
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26. 1. Non-Metals are Not Malleable. Non-Metals are Brittle.
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32. Pure Substances : Elements and Compounds
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33. 3. Metals are Good Conductors of Heat and Electricity.
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34. 4. Non-Metals are Not Lustrous (Not Shiny). They are Dull in Appearance.
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37. 1. Separation by a Suitable Solvent
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38. Solutions, Suspensions And Colloids
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46. Differences Between Mixtures and Compounds
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48. Separation Of Mixture Of a Solid And a Liquids
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50. To Separate the Salt-Water Mixture (or Salt-Solution)
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