NCERT Solutions for class 6 Science Separation of Substances

Exercises

Q1: Why do we need to separate different components of a mixture? give two examples.

Ans: We need to separate substances to get useful ones out from the rest of the materials.

Example:

1. Stones from rice can be separated with the help of hands.
2. A strainer can be used to separate tea leaves from tea.

Q2: What is winnowing? where is it used?

Ans: Winnowing is a method, which is used to separate the heavier particles from the lighter ones. It is mainly used to separate heavier grains from their lighter husks.

Q3: How will you separate husk or dirt particles from a given sample of pulses before cooking?

Ans: We can separate the husk or dirt particles from a given sample of pulses with our hands just before cooking.

Q4: What is sieving? where is it used?

Ans: Sieving is a method of separation which is used to separate bigger particles from smaller ones with the help of a sieve. It is mainly used to separate flour from dirt particles. It is also used to separate pebbles from sand at construction sites.

Q5: How will you separate sand and water from their mixture?

Ans: Sand and water can be separated from their mixture by sedimentation and decantation.

1. First, You have to left the mixture of sand and water undisturbed for a long time.
2. Second, the sand will settle at the bottom of the container, which is known as sedimentation.
3. Third, pour the clear water into another container which is known as decantation.

Q6: Is it possible to separate sugar mixed with wheat flour? if yes how will you do it?

Ans: Yes, it is possible to separate sugar mixed with wheat flour by the sieving method. Due to variation in the size of sugar and wheat flour, the wheat flour will pass through the holes of the sieve whereas the sugar will stay in the sieve.

Q7: How would you obtain clear water from a sample of muddy water?

Ans: Filtration can be used to obtain clear water from muddy water.

1. First, you have to put a filter paper on a clean container.
2. Second, pour the muddy water through the filter paper.
3. Third, the mud will collect on the filter paper whereas the clear water will collect in the clean container.

Q8: Fill up the blanks

1. The method of separating seeds of paddy from its stalk is called threshing.
2. 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.
3. Salt is obtained from seawater by the process of evaporation.
4. Impurities settled at the bottom when muddy water was kept overnight in a bucket. The clear water was then poured off from the top. The process of separation used in this example is called sedimentation and decantation.

Q9: True or false

1. A mixture of milk and water can be separated by filtration. False
2. A mixture of powdered salt and sugar can be separated by the process of winnowing. False
3. Separation of sugar from tea can be done with filtration. False
4. Grain and husk can be separated with the process of decantation. False

Q10: 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 lemon before or after dissolving sugar? In which case would it be possible to dissolve more sugar?

Ans: Ice should be added after dissolving sugar in it because that will make it possible to dissolve more sugar.

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