CBSE Class 6 Science Separation of Substances Assignment

Question. How will you separate husk or dirt particles from a given sample of pulses before cooking?
Answer: Husk and dirt particles are separated from pulses by hand picking.

Question. How would you obtain clear water from a sample of muddy water?
Answer: By Sedimentation and decantation: Allow muddy water to stand. Mud gets settled down in the water. Slowly pour water to another container. We can also obtain pure water from muddy water by filtration.

Question. How will you separate sand and water from their mixture?
Answer: By Sedimentation and decantation: The mixture is allowed to stand without any disturbances, and sand settles down. Now slowly pour the water into another container to obtain sand in the bottom. We can also use filtration.

Question. Why do we need to separate different components of a mixture? Give two examples.
Answer: We need to separate different components of a mixture:
(i) To separate harmful or non-useful substances that may be mixed with it.
(ii) To separate even useful components if we need to use them separately.
Examples: (i) Milk or curd is churned to separate the butter.
(ii) Grain is separated from stalks, while harvesting

Question. Is it possible to separate sugar mixed with wheat flour? If yes, how will you do it?
Answer: Yes. Mix sugar and wheat flour in water. Stir the solution to allow sugar to dissolve. Now filter the mixture. Filtrate contains sugar solution and residue will be wheat flour.

Question. What is sieving? Where is it used?
Answer: Sieving is a method of separation which allows the fine flour particles to pass through the holes of the sieve while the bigger impurities remain on the sieve. It is used at home to separate pebbles and stones from sand.

Question. What is winnowing? Where is it used?
Answer: Method of separating the components from a mixture is known as winnowing. In this method heavier and lighter components of a mixture are separated by wind or by blowing air. This method is used to separate grains from husk.

Question. 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 after dissolving sugar because the dissolving power of water decreases with decrease in temperature. So, if we add ice before dissolving sugar, less amount of sugar will get dissolved.

Fill in the blanks:

Question. Salt is obtained from seawater by the process of ............
Answer: Evaporation

Question. 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 .....................
Answer: Sedimentation and decantation

Question. The method of separating seeds of paddy from its stalks is called ...............
Answer: Threshing

Question. 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 ...........
Answer: Filtration

True or false:

Question. Separation of sugar from tea leaves can be done with filtration. 
Answer: True

Question. Grain and husk can be separated with the process of decantation. 
Answer: False

Question. A mixture of milk and water can be separated by filtration. 
Answer: False

Question. A mixture of powdered salt and sugar can be separated by the process of winnowing. 
Answer: False

Separation of Substances

1) Fill in the blanks _____

a. The method of separating mixture into its component by hand is called a ________.
Answer: handpicking
In simple words: Picking out unwanted substances by hand from a mixture is known as handpicking.

Exam Tip: Handpicking is useful when the quantity of impurities is small and particles are large enough to be seen easily.

b. __________ is the method of separting husk from grains using wind.
Answer: Winnowing
In simple words: Wind blows away light husk while heavy grains fall straight down.

Exam Tip: Remember that winnowing relies on the difference in weights of components using wind or blowing air.

c. The process of settling down of a solid at the bottom of liquid is called a _________.
Answer: sedimentation
In simple words: When heavier solid particles settle at the bottom of a liquid over time, it is called sedimentation.

Exam Tip: Do not confuse sedimentation with decantation; sedimentation is the settling process.

d. A substance that dissolves in liquid is called a ____________.
Answer: solute
In simple words: The solid or substance that gets dissolved is the solute.

Exam Tip: Solute dissolves in a solvent to form a solution.

e. The mixture of a solute and a solvent is called a _____________.
Answer: solution
In simple words: A uniform mixture formed when a solute dissolves in a solvent.

Exam Tip: Solution = Solute + Solvent.

2) MCQ - Tick ( ) the correct option __

I Water is called a universal solvent because ____
(a) It can dissolve very few solid.
(b) It cannot dissolve any substance in it.
(c) It can dissolve only liquids.
(d) It can dissolve many solids, liquids and gases.
Answer: (d) It can dissolve many solids, liquids and gases.
Water dissolves a large variety of substances, which is why it is termed a universal solvent.
In simple words: Water dissolves more substances than any other liquid.

Exam Tip: Learn the definition of a universal solvent.

II A solution is said to be saturated if _____
(a) It can dissolve more of the substance in it.
(b) It cannot dissolve more of the substance in it.
(c) It can be filtered.
(d) It becomes very sweet.
Answer: (b) It cannot dissolve more of the substance in it.
A saturated solution has reached its maximum capacity to dissolve a solute at a given temperature.
In simple words: No more solute can dissolve in a saturated solution.

Exam Tip: Key keyword for saturation is "no more substance can be dissolved".

III The most convenient method for separating husk (bhusoa) from grain is___
(a) Decantation
(b) Handpicking
(c) Filteration
(d) Winnowing
Answer: (d) Winnowing
Winnowing uses wind energy to separate lighter husk from heavier grains efficiently.
In simple words: Winnowing separates husk from grain using wind.

Exam Tip: Husk is lighter than grain, making winnowing the ideal separation technique.

IV A mixture of coconut oil and water can be separated by _____
(a) Filteration
(b) Decantation
(c) handpicking
(d) Evaporation and condensation
Answer: (b) Decantation
Coconut oil and water form two separate layers because they are immiscible liquids, which can be separated by decantation or using a separating funnel.
In simple words: Two liquids that do not mix form layers and can be separated by pouring off the top layer.

Exam Tip: Immiscible liquids of different densities separate into layers.

V Peanuts are reparated from a mixture of pulses and rice by _______
(a) Winnowing
(b) Filteration
(c) Sieving
(d) handpicking
Answer: (d) handpicking
Peanuts are large enough and easily distinguishable from pulses and rice, allowing them to be picked out by hand.
In simple words: Large components like peanuts are easily picked out by hand.

Exam Tip: Handpicking is best for large-sized impurities or components.

3. Coin one word for the following ___
a. The process of converting a liquid into its vapour ___________.
Answer: Evaporation
In simple words: Changing liquid into vapor state by heating is evaporation.

Exam Tip: Evaporation is used to obtain salt from sea water.

b. A substance that settles down at the bottom of a liquid ___________.
Answer: Sediment
In simple words: The solid particles that settle down are called sediment.

Exam Tip: Sediment is the noun for the settled solid matter.

c. A solution in which no more solute can be dissolved at a given tempoerature ___________.
Answer: Saturated solution
In simple words: A solution holding the maximum possible amount of solute.

d. The process of converting water vapour into water drops. ___________.
Answer: Condensation
In simple words: Turning vapor back into liquid is condensation.

Exam Tip: Condensation is the reverse of evaporation.

4. Label the following diagram and Name the process method ___
A - Filter paper
B - Funnel
C - Filtrate
D - Stand
Answer:
Method - Filtration
In simple words: Filtration uses a porous barrier like filter paper to separate insoluble solids from liquids.

Exam Tip: The clear liquid passing through is filtrate, and the solid left behind is the residue.

5. Answer the following _
i. Is milk a mixture?
Answer: Yes, milk is a mixture of water, fat, proteins, and lactose.
In simple words: Milk contains multiple substances mixed together physically.

Exam Tip: Natural food items like milk and butter are mixtures.

ii. Can filteration be used to seperate the components of milk.
Answer: No, filtration cannot separate the components of milk because the fat and protein particles are extremely small and pass right through standard filter paper. (Special processes like centrifugation are required).
In simple words: Filter paper cannot separate dissolved or very fine particles present in milk.

Exam Tip: Filtration only separates insoluble solid particles larger than filter pores.

iii. What is the process of removal of the clear liquid layer without disturbing the settled solid called ?
Answer: Decantation
Answer: Decantation
In simple words: Pouring out the top liquid gently without disturbing the sediment below is decantation.

Exam Tip: Decantation follows sedimentation.

6. Mention the method / process involve against the pictures _
a. 1 ......................................................
Answer: Handpicking
In simple words: Separating stones or impurities from grains by hand.

Exam Tip: Image shows manual sorting of grains.

b. 2 ......................................................
Answer: Winnowing
In simple words: A person dropping grain from a height so wind blows away the husk.

Exam Tip: Image shows traditional winnowing outdoors.

c. 3. a) ....................................
b) ....................................
Answer:
a) Evaporation
b) Condensation
In simple words: Boiling water turns it to vapor (evaporation), and cooling vapor on a plate forms water drops (condensation).

Exam Tip: This setup demonstrates obtaining pure water from a solution (distillation process components).

d. 4 a) ....................................
b) ....................................
Answer:
a) Sedimentation
b) Decantation
In simple words: Mud settles down at the bottom (sedimentation), and clear water is poured into another container (decantation).

Exam Tip: These two steps are generally used sequentially for muddy water.