Separation of Substances Class 6 MCQ with Answers

MCQs and Mock Test | NCERT - CBSE Chapter 5

Practice Separation of Substances Class 6 MCQs with answers.
Learn handpicking, threshing, winnowing, sieving, sedimentation, decantation, filtration, evaporation - with instant answers and performance report.

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Quick Revision: Separation of Substances

  • Handpicking: Manual separation of larger impurities like stones from grains.
  • Threshing: Beating stalks to separate grain seeds from stalks.
  • Winnowing: Using wind to separate lighter husk from heavier grains.
  • Sieving: Separating particles of different sizes using a sieve.
  • Sedimentation: Heavier insoluble solids settle down when mixture is allowed to stand.
  • Decantation: Pouring out liquid without disturbing settled sediment.
  • Filtration: Using a filter (strainer, cloth, filter paper) to separate solids from liquids.
  • Evaporation: Conversion of water into water vapour by heating.
  • Condensation: Conversion of water vapour into liquid upon cooling.
  • Saturated Solution: A solution that cannot dissolve more of a substance at a given temperature.
  • Loading: Adding alum to muddy water to make impurities settle faster.

Separation of Substances Class 6 Questions and Answers (FAQ)

Why do we need to separate substances from mixtures in Class 6 Science?
We separate substances from mixtures for several reasons: to remove harmful or non-useful components (like stones from rice), to obtain useful components (like butter from milk), to separate two useful components from each other (like salt from seawater), and to purify substances. The method used depends on the properties of the components in the mixture.
What is the difference between winnowing and sieving?
Winnowing separates lighter components from heavier ones using wind or air current - for example, separating husk from grain. Sieving separates particles based on size differences - smaller particles pass through the sieve while larger particles remain on top. Winnowing is based on weight difference, while sieving is based on particle size difference.
What is the difference between sedimentation and decantation?
Sedimentation is the process where heavier insoluble particles naturally settle at the bottom of a liquid when the mixture is left undisturbed. Decantation is the process of carefully pouring out the clear liquid from the top without disturbing the settled sediment. These two processes are often used together - first sedimentation to let particles settle, then decantation to pour off the clear liquid.
What is a saturated solution and how does temperature affect it?
A saturated solution is one that cannot dissolve any more solute at a given temperature - the solute starts settling at the bottom. The solubility of most solid substances increases with temperature. So, when a saturated solution is heated, it can dissolve more solute and becomes unsaturated. On cooling, the extra dissolved solute may crystallize out.
How is common salt obtained from seawater by evaporation?
Seawater contains dissolved salt. It is trapped in shallow ponds called salt pans and left to evaporate in the sun. As water evaporates, the concentration of salt increases. Once all the water has evaporated, common salt remains behind. This method is called evaporation and is widely used to obtain salt from seawater on a commercial scale.

Chapter Summary: Separation of Substances

We separate substances from mixtures for various reasons: to remove harmful or non-useful components, to obtain useful components, or to separate two useful components. Different separation methods are used based on the properties of the components.

Handpicking is used for large impurities. Threshing separates grains from stalks. Winnowing uses wind to separate lighter husk from heavier grains. Sieving separates particles of different sizes. Sedimentation and decantation separate insoluble solids from liquids by allowing settling and pouring off the liquid. Filtration uses a porous filter to separate solids from liquids. Evaporation converts water to vapour, leaving behind dissolved solids. Condensation converts vapour back to liquid. A saturated solution cannot dissolve more solute at a given temperature; heating can increase solubility.

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