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CHEMISTRY [5 Mark Question Answer]

Elements, Compounds and Mixtures · ICSE STD 7 (ICSE - English Medium). 3 questions.

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[5 Mark Question Answer]

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Question 15 Marks
Name the process by which the components of following mixtures can be separated.
  1. Iron and sulphur
  2. Ammonium chloride and sand
  3. Common salt from sea water
  4. Chaff and grain
  5. Water and mustard oil
  6. Sugar and water
Answer
  1. Magnetic separation.
  2. Sublimation.
  3. Evaporation.
  4. Winnowing separates chaff (lighter) from heavier grains in two different heaps.
  5. Mustard oil and water is liquid-liquid immiscible mixture and is separated by separating funnel. Water being the heavier forms the lower layer.
  6. By evaporation in this process of converting a liquid into its vapour state by heating. Liquid is heated and water evaporate and sugar is obtained.
  7. Centrifugation
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Question 25 Marks
State four difference between compounds and mixtures.
Answer
Compound Mixture
1. A compound is a pure substance. 1. A mixture is an impure substance.
2. Compounds are always homogeneous. 2. Mixtures may be homogeneous or heterogeneous.
3. A compound has a fixed composition, i.e., it is formed when two or more pure substances chemically combine in a definite ratio by mass. 3. A mixture has no fixed composition, i.e., it is formed by mixing two or more substances in any ratio without any chemical reaction.
4. Formation of a compound involves change in energy. 4. Formation of a mixture does not involve any change in energy.
5. Compounds have specific set of properties. 5. Mixtures do not have any specific set of properties.
6. Components of compounds can be separated only by complex chemical processes. 6. Components of mixtures can be separated by simple physical methods.
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Question 35 Marks
What is the difference between a pure substance and a mixture ?
Answer
  • A pure substance consists of only one kind of matter, that is, all the particles are same. It has a definite composition and constant properties. It cannot be split into simpler substances by physical means. All pure substances have characteristic melting and boiling points. A pure substance is either a compound or an element.
  • A Mixture contains two or more substances in any proportion which can be separated by physical methods. Mixtures are generally of two types : Homogeneous and Heterogeneous.
    In a mixture, the constituents can be present in any ratio. They do not have characteristic melting and boiling points. In a mixture each constituent retain its original properties. These can be separated by physical means.
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[5 Mark Question Answer] - CHEMISTRY STD 7 Questions - Vidyadip