NCERT Solutions for Class 6th Science

Chapter 5 - SEPARATION OF SUBSTANCES

 (Complete Downloadable Chapter Solution PDF file is at the bottom of the page)

 

Q.1      Why do we need to separate different components of a mixture? Give two examples.

Ans     We need to separate different components of a mixture:

            a) To separate two different,but useful components.

            b) To remove non-useful components.

            c) To remove impurities or harmful components.

            Examples:

            1) Separating tea leaves with a stainer after preparing tea.

            2) Separating butter by churning milk or curd.

 

Q.2      What is winnowing? Where is it used?

Ans     Winnowing is the method to separate heavier and lighter components of a mixture by wind or by blowing air. This               method is commonly used by farmers to separate lighter husk particles from heavier seeds of grain.

 

Q.3      How will you separate husk or dirt particles from a given sample of pulses before cooking.

 

Q.4      What is sieving? Where is it used?

 

Q.5      How will you separate sand and water from their mixture?

 

Q.6      Is it possible to separate sugar mixed with wheat flour? If yes, how will you do it?

 

Q.7      How would you obtain clear water from a sample of muddy water?

Ans     The mixture should be allowed to remain undisturbed for sometime. This makes mud to settle down. This process               is called sedimentation. The water then can be poured in another container. This method is called decantation.                     Now the smaller mud particles still present in the water can be removed by the process of filtration using filter                     like cloth or filter paper etc.

 

Q.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 from the top. The process of separation used in this example is called _______.

 

Q.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.

 

Q.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?

Ans      We should add ice to the lemonade after dissolving sugar. It would be possible to dissolve more sugar in this case                 as saturation level increases with the increase in temperature i.e more sugar can be dissolved in warm water.