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(a) Why is crystallisation technique bet...

(a) Why is crystallisation technique better than evaporation ?
(b) Write any two physical properties each of metals and non-metals.
(c ) Name the technique used to separate butter from curd.

Text Solution

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(a) Both these techniques are used to separate the solid substances from their solutions. But crystallisation is considered better because during evaporation certain solids may decompose or some of them like sugar get charred when the solution is evaporated completely to dryness. As a result of crystallisation, even the shapes of the crystals donot change.
(b) (i) Metals have a shining surface known as lustre.
(ii) Metals are malleable and ductile.
(iii) Non-metals are mostly poor conductors of electricity.
(iv) Non-metals are generally soft.
(c ) Butter can be separated from curd by the process of centrifugation. This is usually done by churning which is very common as well as convenient.
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Knowledge Check

  • Crystallisation is a process that separates a pure solid in the form of its crystals from a solution. A solid can also be separated from its solution by evaporation. However crystallisation technique is better than simple evaporation technique. We can get an impure sample of a solid even after evaporation. Some solids decomposes or some may get charred on heating to dryness during evaporation. Crystallisation is a better process than evaporation because

    A
    it takes lesser time
    B
    some impurities may remain in the filtrate which remain with the solid after evaporation
    C
    some solid is lost during evaporation
    D
    chemical properties change during evaporation

  • Crystallisation is a process that separates a pure solid in the form of its crystals from a solution. A solid can also be separated from its solution by evaporation. However crystallisation technique is better than simple evaporation technique. We can get an impure sample of a solid even after evaporation. Some solids decomposes or some may get charred on heating to dryness during evaporation. In which of the following processes, crystallisation is used.

    A
    Purification of salt that we get from sea water.
    B
    To separate salt from sea water.
    C
    To separate camphor from salt.
    D
    To separate colours in a dye.

  • Crystallisation is a process that separates a pure solid in the form of its crystals from a solution. A solid can also be separated from its solution by evaporation. However crystallisation technique is better than simple evaporation technique. We can get an impure sample of a solid even after evaporation. Some solids decomposes or some may get charred on heating to dryness during evaporation. What type of mixtures are separated by crystallisation?

    A
    A mixture in which one component is soluble in a solvent.
    B
    A mixture in which impurities are soluble in a solvent.
    C
    A mixture in which both the components are soluble in a solvent.
    D
    A mixture in which both the components are insoluble in water.

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