1 March 2015

CBSE-NCERT Solution : Separation of Substances

CBSE NCERT Class VI (6th) | Science | Chemistry

Chapter  :  Separation of Substances

CBSE NCERT Solved Question Answer

Ql. Why do we need to separate the components of a mixture?
Ans. Components of a mixture need to be separated in order to:
1.      remove undesirable waste
2.      remove harmful components from a mixture
3.      obtain useful components
4.      obtain the pure sample of a substance.

Must Read:Separation of Substances - Chapter Summary
Q2. Name the different methods of separation of substances.
Ans. Different methods of separation of substances are:
1.      handpicking
2.      threshing
3.      winnowing
4.      sieving
5.      magnetic separation
6.  sedimentation & decantation
7.  filtration

Q3. Define the terms:
a) Threshing
Threshing is the process in which stalks are beaten to separate grains from the stalks.
b) Winnowing
Winnowing is the method of separating husk from grains with the help of wind.

Q4. What type of mixtures can be separated by hand-picking?
Ans. Hand-picking is usually used to separate those mixtures where one of the components is in small quantity and can be easily picked up by hand. Example: stones from rice and pulses.

Q5. What is the principle behind sieving?
Ans. Sieving is used to separate those solid mixtures which have components of different sizes. Larger particles are retained on the sieve and the smaller particles pass through the pores of the sieve.
Example: a mixture of sand and stone can be separated by using a sieve.

Q6. What do you mean by the terms sedimentation and decantation?
Ans. Sedimentation: it is the process of setting down the insoluble component of a mixture on leaving undisturbed for sometime.
Decantation: The process of pouring of a liquid from a vessel without disturbing the sediment is called decantation.

Q7. What is filtration?
Ans. The process of removing insoluble solids from a liquid by using a filter paper is known as filtration.

Q8. Discuss evaporation and condensation as methods of separation.
Ans. Evaporation is a method of obtaining soluble solids from their solutions by heating. In this process the liquid changes into its vapours by heating the solution and the soluble solid is left behind.
On the other hand, condensation is the process of changing back of the hot vapours into the liquid state by cooling.

Q9. What is a saturated solution?
Ans. A solution in which no more of solute can be dissolved in the solvent at a given temperature is known as a saturated solution.

Ql0. What happens if the saturated solution of a substance in water is:
a) heated?                   b) cooled?
Ans. a) If the saturated solution of a substance in water is heated then the undissolved solute will dissolve.
a)       ) If the saturated solution of a substance in water is cooled then some of the dissolved substance will reappear in the form of solid crystals.
CBSE NCERT Class VI (6th) | Science |  | Chemistry, Separation of Substances,  CBSE NCERT Solved Question Answer, CBSE NCERT Solution.
Ql1. How is cream obtained from milk?
Ans. When milk is churned or rotated at a high speed, cream gets separated from milk.

Ql2. You are given a mixture of salt & sand, how would you separate them?
Ans. For separating the given mixture of salt & sand following steps are carried out:
        add water to the given mixture and allow it to stand undisturbed
        sand particles settle down at the bottom of the container & salt gets dissolved
        sand can be separated by filtration leaving behind salt solution
        salt can be obtained from the solution by evaporation.

Ql3. How would you separate a mixture of sand & iron fillings?
Ans. The mixture can be separated by the method of magnetic separation .