NCERT Solutions Std 6 Science Separation of Substances

Separation of Substances

Exercise:

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

     We need to separate harmful substances or non-useful substances that may be mixed with them. Sometimes, we separate even useful components if we need to use them separately.

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

      Winnowing is a method of separating substances. It is used 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.

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

      We separate husk or dirt particles from a given sample of pulses before cooking by handpicking and sieving.

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

      Sieving is a process that allows very fine particles to pass through the holes of the sieve while the bigger impurities remain on the sieve.

      Sieving is used at houses, flour mills,s and construction sites.

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

     Sand and water can be separated by the methods of sedimentation and decantation. The mixture of sand and water is kept without disturbing for some time. The sand is heavier than water, therefore it settles down at the bottom. The water which is in the upper layer is poured into some other container. In this way, the water is separated from the mixture of sand.

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

     Yes, we can separate sugar mixed with wheat flour. With the help of a sieve, we can separate sugar from flour.

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

     We will obtain clear water from a sample of muddy water by the method of filtration.

8). Fill up the blanks.

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

9). True or false?

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 of sugar from tea can be done with filtration.

     False.

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

     False.

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?

     We should to add ice to the lemonade after dissolving the sugar. 

 

Additional questions:

Q 1). State whether True or False.

1). Handpicking is used to separate dirt and husk from grains.

    True.

2). Wind manages to separate substances during threshing.

     False

 Wind manages to separate substances during winnowing.

3). Sieving is used when components of a mixture have same sizes.

     False.

Sieving is used when components of a mixture have different sizes.

4). Sometimes, it may not be possible to separate components of a mixture by winnowing and handpicking.

     True.

5) Decantation is used to separate oil and water.

     True.

6) Machines are also used to thresh large quantities of grain.

     True.

7). The process of evaporation takes place continuously wherever water is present.

     True.

 

Q 2). Fill in the blanks.

1). The process that is used to separate grains from the stalks is threshing.

2). The separated husk is used for many purposes such as fodder for cattle.

3). Water dissolves different substances in different amounts.

Q 3). Distinguish between evaporation and condensation.

Evaporation Condensation
1. The process of conversion of water into its vapour is called evaporation. 1. The process of conversion of water vapour into its liquid form is called as condensation.
2. Evaporation can be used to separate a solid dissolved in a liquid. 2. Condensation is used to obtain liquid form of the gaseous substance.

 

 

Q 4). Define:

i). Sedimentation

     The process in which the heavier component in a mixture solution settles after water is added to it is called sedimentation.

ii). Evaporation

     The process of conversion of water into its vapour is called evaporation.

iii). Condensation

     The process of conversion of water vapour into its liquid form is called as condensation.

iv). Saturated solution

     A saturated solution is one in which no more of that substance can be dissolved.

Q 5). Name the methods of separating substances.

     The methods of separating substances are handpicking, winnowing, threshing, sieving, sedimentation, decantation, and filtration.

Q 6). Write a note on

i). Handpicking:

     The method of handpicking can be used for separating slightly larger-sized impurities like pieces of dirt, stone, and husk from wheat, rice, or pulses. Handpicking is a convenient method of separating the substances when the quantity of such impurities is usually not very large.

ii). Threshing

     The process of threshing is used to separate the grain from stalks. In this process, the stalks are beaten to free the grain seeds. Sometimes, threshing is done with the help of bullocks. Machines are also used to thresh large quantities of grain.

iii). Winnowing

     Winnowing is a method of separating substances. It is used 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. The husk particles are carried away by the wind. The seeds of grain get separated and form a heap near the platform for winnowing. The separated husk is used for many purposes such as fodder for cattle.

Q 7). Choose the correct option

1). Separating the wheat grain from the stalk of a wheat plant.

 a). winnowing                                   b). hand picking

c). threshing                                      d). sieving

answer:

threshing.

2). Separating pieces of stone and husk from rice and pulses.

 a). winnowing                                   b). hand picking

c). threshing                                      d). sieving

answer:

handpicking

3). The method of separating heavier substances and lighter substances.

 a). winnowing                                   b). hand picking

c). threshing                                      d). sieving

answer:

winnowing

4). Seeds and solid particles of pulp from fruit juices are separated by the method of-

 a). sedimentation                             b). hand picking

c). filtration                                      d). evaporation

answer:

filtration

 

 

5). Separating tea leaves from prepared tea by the method of-

 a). sedimentation                               b). hand picking

  c). filtration                                      d). evaporation

answer:

filtration

6). Which of the method is not used by the farmers

 a). winnowing                               c). threshing                         b). sieving

answer:

sieving

7). Common salt is obtained from the seawater by the method of-

 a). sedimentation                              b). hand picking

  c). filtration                                      d). evaporation

answer:

evaporation.

8). The process of settling heavier components is called –

 a). sedimentation                            b). hand picking

c). filtration                                      d). evaporation

answer:

sedimentation.

 

 

 

 

 

 

 

 

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