To Study the Properties of a Compound of Iron and Sulphur
When the mixture of iron filings and sulphur powder is heated, a black compound known as iron sulphide () is formed. Let us examine the properties of this compound to find out the difference between a compound and a mixture.
1.If a tnagnet is put in the iron sulphide compound, iron does not get separated from sulphur (see Figure 21). Even carbon disulphide solvent cannot separate the sulphur from iron sulphide compound.This means that the iron sulphide compound cannot be separated into its constituents by physical methods.In general we can say that a compound cannot be separated into its components by physical methods.
2.When dilute sulphuric acid is added to iron sulphide compound, we get a colourless, foul smelling gas called hydrogen sulphide (having the smell of rotten eggs). No hydrogen gas is formed in this case. This means that iron sulphide does not show the properties of iron present in it. Even the sulphur present in iron sulphide compound cannot be dissolved by carbon disulphide. This means that iron sulphide compound does not show the properties of sulphur. From this we conclude that iron sulphide compound does not show the individual properties of its constituents, iron and sulphur. The properties of iron sulphide compound are entirely different from those of its constituents, iron and sulphur. In general we can say that the properties of a compound are entirely different from those of its constituent elements.
3.Iron sulphide compound is prepared by heating together iron filings and sulphur. Once the reaction starts, a lot of heat and light are produced during the preparation of iron sulphide compound. From this we conclude that energy (in the form of heat, light, etc.) is usually either given out or absorbed during the preparation of a compound.The formation of compound is a chemical change.
4.Iron sulphide compound is prepared by heating together 7 parts by mass of iron and 4 parts by mass of sulphur (Atomic masses : Fe = 56 u, S = 32 u, so Fe : S = 56 u : 32 u or 7 : 4). If we take more of iron or sulphur, the excess part remains unreacted. Thus, iron sulphide compound is always made up of the same elements, iron and sulphur, combined together in a fixed proportion by mass. Since the composition of iron sulphide compound is fixed, it has a definite formula, FeS. From this discussion we conclude that the composition of a compound is fixed, the constituents are present in a fixed proportion by mass.A compound has a definite formula.
5.Iron sulphide compound melts at a definite temperature. From this we conclude that a compound has a fixed melting point, boiling point, etc.
6.If the iron sulphide compound is viewed through a magnifying glass, no separate particles of iron or sulphur are seen and it appears to be just the same throughout its mass. From this we conclude that a compound is a homogeneous substance.We will now write down the differences between compounds and mixtures in a tabular form.
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Matter in Our Surroundings - Notes
1. The Case of a Liquid Solute Dissolved in a Liquid Solvent
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2. 11. Metals Usually Have a Silver or Grey Colour
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8. 7. Non-Metals may be Solid, Liquid or Gases at the Room Temperature.
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10. 6. Metals are Usually Strong. They Have High Tensile Strength.
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11. 3. Non-Metals are Bad Conductors of Heat and Electricity.
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16. Chemical Formula for daily use material
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27. 4. Metals are Lustrous (or Shiny), and can be Polished.
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30. To Study the Properties of a Compound of Iron and Sulphur
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34. 7. Metals are Solids at the Room Temperature
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36. To Study the Properties of a Suspension
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38. To Study the Properties of a Solution
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39. Experiment to Obtain Coloured Component (Dye) From Ink
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42. 6. Non-Metals are Not Strong. They Have Low Tensile Strength.
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44. 8. Non-Metals Have Comparatively Low Melting Points and Boiling Points
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48. To Separate a Mixture of Alcohol and Water
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49. 8. Metals Generally Have High Melting Points and Boiling Points.
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50. 1. Non-Metals are Not Malleable. Non-Metals are Brittle.
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