NCERT Solutions Class 6 Science Chapter 5 Separation of Substances

NCERT Solutions for Class 6 Science for chapter 5 Separation of Substances

Question.1

Why do we need to separate different components of a mixture? Give two examples.

Answer.

Different components of a mixture are separated either to separate undesired components, impurities or to obtain more than one useful components from the mixture.

Examples:

1) Small stone pieces and unwanted seed grains are removed from rice or dal before cooking.

2) From petroleum useful components like petrol, diesel kerosene, etc. are separated.

Question.2

What is winnowing? Where is it used?

Answer.

Winnowing is a process of separating heavier and lighter components of a mixture by wind or by blowing air. This method is based on the property that grains are heavier than husk and hay. Farmers use this method to separate grains from husk and hay.

Question.3

How will you separate husk or dirt particles from a given sample of pulses before cooking?

Answer.

Husk or dirt particles from the given sample of pulses can be separated by sedimentation. In this process, water is added to the pulses. Pulses being heavier settle down at the bottom and the impurities like husk and dust particles go into water. Water along with dust particles is removed by the process of decantation, leaving the pulses at the bottom.

Question.4

What is sieving? Where is it used?

Answer.

Sieving is the process of separating solid components of a mixture varying in size. In this process sieves with holes of proper size is used. Sieving allows the fine particles to pass through the holes of sieves, leaving behind the bigger particles on the sieve. Husk and stones from wheat are separated by sieving.

Question.5

How will you separate sand and water from their mixture?

Answer.

Mixture of sand and water can be separated by two methods:

1) Combination of sedimentation and decantation

Combination of sedimentation and decantation: Take the mixture of sand and water in a container and allow the mixture to stand for some time. Sand particles being heavier settle down at the bottom. This process is called sedimentation. Water is poured out into another container without disturbing sand. This process is called decantation.

2) Filtration

Question.6

Is it possible to separate sugar mixed with wheat flour? If yes, how will you do it?

Answer.

Yes, it is possible to separate sugar from wheat flour. Mixture of sugar and wheat flour is allowed to pass through sieve. Wheat flour particles being fine pass through the holes of sieve and  sugar remains on the sieve.

Question.7

How would you obtain clear water from a sample of muddy water?

Answer.

Clear water from the sample of muddy water can be obtained by the process of filtration. Muddy water is allowed to pass through muslin cloth or filter paper. Water passes through the muslin cloth and mud particles remain on the muslin cloth.

Question.8

Fill up the blanks

(a) The method of separating seeds of paddy from its stalks is called _______.

(b) When milk, cooled after boiling, is poured onto a piece of cloth the cream (malai) is left behind on it. This process of separating cream from milk is an example of _______.

(c) Salt is obtained from seawater by the process of _________.

(d) Impurities settled at the bottom when muddy water was kept overnight in a bucket. The clear water was then poured off the top. The process of separation used in this example is called _______.

Answer.

(a) The method of separating seeds of paddy from its stalks is called threshing.

(b) When milk, cooled after boiling, is poured onto a piece of cloth the cream (malai) is left behind on it. This process of separating cream from milk is an example of filtration.

(c) Salt is obtained from seawater by the process of evaporation.

(d) Impurities settled at the bottom when muddy water was kept overnight in a bucket. The clear water was then poured off the top. The process of separation used in this example is  called decantation.

Question.9 - True or false?

(a) A mixture of milk and water can be separated by filtration.

(b) A mixture of powdered salt and sugar can be separated by the process of winnowing.

(c) Separation of sugar from tea can be done with filtration.

(d) Grain and husk can be separated with the process of decantation.

Answer.

(a) A mixture of milk and water can be separated by filtration. (False)

(b) A mixture of powdered salt and sugar can be separated by the process of winnowing. (False)

(c) Separation sugar from tea can be done with filtration. (Flase)

(d) Grain and husk can be separated with the process of decantation. (False)

Question.10 Lemonade is prepared by mixing lemon juice and sugar in water. You wish to add ice to cool it. Should you add ice to the lemonade before or after dissolving sugar? In which case would it be possible to dissolve more sugar?

Answer.

We should add ice to the lemonade after dissolving sugar. More sugar can be dissolved before adding ice to the lemonade. This is because sugar dissolves very slowly in cold water.