Chemistry

Matter in Our Surroundings


Compounds


A compound is a substance made up of two or more elements chemically combined in a fixed proportion by mass. For example, water (H2O) 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 (NH4C1) is a compound made up of three elements,nitrogen, hydrogen and chlorine; sand (silicon dioxide, SIO2) is a compound of silicon and oxygen, and marble (calcium carbonate, CaCO3) is a compound made up of calcium, carbon and oxygen elements.
Some more examples of compounds are : Ammonia (NH3), Carbon dioxide (CO2), Ice (H2O), Steam (H2O),Chalk (Calcium carbonate, CaCO3), Limestone (Calcium carbonate, CaCO3), Lime or Quicklime (Calcium oxide, CaO), Slaked lime [Calcium hydroxide, Ca(OH)2], Methane (CH4), Glucose (C6H12O6), Sugar or Canesugar (C12H22O11), Starch [(C6H10O5)n], Baking soda (Sodium hydrogencarbonate, NaHCO3), Washing soda (Sodium carbonate, Na2CO3), Potassium nitrate (KN03), Potassium sulphate (K2SO4), Sodium sulphate (Na2SO4), Copper sulphate (CuSO4), Iron sulphide (FeS), Hydrochloric acid (HC1), Sulphuric acid (H2SO4),Nitric acid (HNO3), Hydrogen bromide (HBr) and Sodium hydroxide (NaOH). 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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Notes


Matter in Our Surroundings - Notes
1. 9. Non-Metals Have Low Densities.
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2. 2. Metals are Ductile.
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3. 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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5. Properties of Metals
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6. 11. Non-Metals Have Many Different Colours.
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7. The Case of Solutions
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8. Concentration of a Solution
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9. 3. Separation by a Magnet
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10. 7. Non-Metals may be Solid, Liquid or Gases at the Room Temperature.
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11. Impure Substances: Mixtures
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12. Non-Metals
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13. 5. Non-Metals are Generally Soft
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14. Is Matter Around Us Pure
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15. Elements
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16. 6. Separation by Distillation
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17. 8. Non-Metals Have Comparatively Low Melting Points and Boiling Points
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18. 8. Metals Generally Have High Melting Points and Boiling Points.
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19. Types of Solutions
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20. 2. Separation by Centrifugation
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21. 1. Metals are Malleable.
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22. Solutions
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23. To Study the Properties of a Suspension
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24. Physical And Chemical Changes
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25. Pure Substances : Elements and Compounds
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26. Properties of a Suspension
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27. Metals
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28. Effect of Temperature and Pressure on Solubility
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29. 1. Non-Metals are Not Malleable. Non-Metals are Brittle.
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30. 2. Non-Metals are Not Ductile.
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31. 10. Non-Metals are Not Sonorous.
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32. Separation of the Gases of the Air
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33. To Study the Properties of a Solution
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34. 4. Purification by Crystallisation
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35. 1. Separation by Fractional Distillation
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36. Chemical Formula for daily use material
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37. Solutions, Suspensions And Colloids
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38. Chemical Changes
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39. Separation of Scrap Iron
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40. Separation Of Mixture Of a Solid And a Liquids
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41. To Separate the Salt-Water Mixture (or Salt-Solution)
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42. 2. Separation by a Separating Funnel
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43. Metals, Non-Metals and Metalloids
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44. 5. Metals are Generally Hard
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45. 9. Metals Have High Densities.
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46. 11. Metals Usually Have a Silver or Grey Colour
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47. 4. Non-Metals are Not Lustrous (Not Shiny). They are Dull in Appearance.
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48. Comparison Among the Properties of Metals and Non-Metals
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49. Compounds
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50. Suspensions
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