CBSE Class 6 Science Separation Of Substances Worksheet Set E

Learning Objectives

1. To understand mixtures and types of mixture.
2. To understand requirement and importance of separation of components of a mixture.
3. To understand different methods of separation .
4. To understand that the choice of the method of separation depends upon the nature of the component ofthe mixture.
5. To understand the different types of solution.
6. To understand the concept of solubility.

MIXTURES
Mixtures are absolutely everywhere you look. Mixtures are the form that are mostly found in nature e.g. rocks, air, or the ocean; they are just about anything you find. They are substances held together by physical forces, not chemical. Two or more substances (either elements or compounds) can be mixed together in any proportion and the resultant substances so obtained are called mixtures (impure substance).

Types of Mixtures
Depending upon the nature of the components that forms the mixture we can have different types of mixtures.

(i) Homogeneous mixture : It is a mixture that has the same composition throughout e.g. a solution of sugar in water. Such a mixture has two or more components.

(ii) Heterogeneous mixture : In such a mixture the particles of each component of the mixture remain separate and can be observed as individual grains under a microscope e.g. mixture of grains and sand.
This type of mixtures contain physically distinct parts and have a nonuniform composition.

REQUIREMENT OF SEPARATION OF MIXTURES
In everyday life, there are many situations in which people want to separate the parts of a mixture. For example, water that contains algae or fish, or
dissolved chemicals from factories is not healthy for drinking purpose. Thus it is preferred to remove it from the water to make it suitable for drinking.
Depending on the mixture involved, separating the component parts can be easy or difficult.
Separating mixtures is a scientific process in which two or more substances are separated which were mixed together. Separating mixtures is useful in

many different ways which are :
1. To remove undesirable components : For example, removal of small stones from rice and pulses before cooking.
2. To obtain useful components : For example, petrol, diesel etc. are obtained from crude oil.
3. To obtain pure substance from mixture : For example, distilled water can be obtained from any water sample by simple distillation.

METHODS OF SEPARATION
Separation methods depends upon the nature of the constituents of the mixture.
To separate a mixture we have to use some property that one constituent of the mixture has and other do not.

Separation of Solid-Solid Mixture
Handpicking : It is the simplest method of separation of substances. This method is used only when unwanted material is in small quantity. Moreover, shape, size, or colour of the unwanted material is different from that of the useful materials. For example, pebbles, broken grains and insects are separated from rice, wheat and pulses, by handpicking.
Threshing : It is the process that is used to separate grains from stalks. In this process stalks are beaten to free the grain seeds. Sometimes this process is carried out with bullocks. In case of large quantities of grains, machines are used for threshing

Winnowing : This process is used to separate heavier and lighter components of a mixture by wind or by blowing air. This is commonly used method to separate lighter husk particles from heavy seeds of grains. It is also used to remove pests from stored grain

Sieving : It is carried out with the help of a sieve. The fine particles pass through the holes of sieve while bigger particles of impurities remain on sieve. It is used at home to separate impurities and bran present in flour. In flour mills this process is used to remove the pieces of stones, stalk and husk from wheat and other grains. In this process the difference in size of particles in a mixture is used to separate them. At construction sites, this process is used to separate pebbles and stones from sand.

Separation of Solid-Liquid Mixture

Sedimentation : When a heavier component in a mixture settles after water is added to it, the process is called sedimentation. The substance deposited is called sediment. This method depends upon the difference in densities of the two components of the mixture. For example, on keeping the tea with the tea leaves, aside for some time the tea leaves begin to settle down.

Decantation : When the liquid layer above the sediment is removed and the sediment is left behind the process is called decantation. For example, when tea leaves settle down, the clear tea (liquor) from the top can be poured into a cup .
Sedimentation can be speeded up by Loading. Alum is used for this purpose.

For example : The dissolved particles of alum load the fine clay particles in water. They become heavier and settle down quickly.

Filtration : This is a method of separation of an insoluble lighter solid and a liquid. The mixture is poured into a filter paper placed in a filter funnel. The liquid or solution passes through the filter paper and is collected in another container placed below the filter funnel. The liquid so collected is called filtrate.
The insoluble solid is left behind at the filter paper. The solid left behind is called residue. The process is called filtration. Difference in size of particles in a mixture is used to separate them
For example, while making cottage cheese(paneer) at home, solid paneer is separated from the liquid by filtration through muslin cloth, a coffee filter separates solid coffee grounds from liquid coffee. Our water supply is filtered through a bed of gravel, sand and charcoal.
Special water filters are used in our homes, colleges and offices for providing safe drinking water. A simple home filter contains a porous candle made up of ceramic or china clay. The water passes through the candle. Candle retains solid impurities but allows the clear water to pass through it.In these filters a special type of light called ultraviolet light is used to kill germs in water.

Separation of Liquid-Liquid Mixture

Evaporation : The process of conversion of water into its vapours is called evaporation. The process of evaporation takes place at all temperatures. It can be speeded up by increase in the temperature. This process is used to obtain common salt (i.e. table salt) from sea water (sea water contains dissolved common salt).
Sea water is collected in shallow ponds and allowed to evaporate in sun. Solid salt is left behind. Salt obtained from this process is not pure and it is purified by crystallisation process.
Crystallisation is used to purify solid substances. In this method pure substance is separated in form of crystal from its hot saturated solution by cooling .

Condensation : It is the process in which the vapours of water (or any other liquid) are allowed to cool and change to liquid state. It is the opposite of evaporation. For example : water vapour condenses into a liquid after making contact with the surface of cold bottle. The process of condensation is also present in air conditioners

Distillation : Distillation is a method of obtaining pure liquid from a solution by using a special apparatus. In this process on heating, a solution, liquid with low boiling point evaporates first. On cooling, vapor condenses to give pure liquid. Distilled water used in lab is obtained by this method.

SOLUTION
A homogeneous mixture of two substances is known as a solution e.g., mixture of sugar and water. When a substance dissolves in a liquid, it breaks up into its individual molecules. These molecules spread out in between the molecules of the liquid. That is why the sugar-water solution tastes sweet.
Solute : The substance present in smaller quantity in a solution is called a solute e.g. in sugar solution, sugar, which is present in smaller quantity is a solute.
Solvent : The substance present in larger quantity in a solution is called a solvent e.g. in sugar solution, water, which is present in larger quantity is a solvent.

Examples of different types of solution :

Substances that dissolve readily in water are said to be soluble in water . 
Substance such as sand do not dissolve in water are said to be insoluble in water.
Some gases such as carbon dioxide and oxygen are soluble in water.
Solubility of oxygen in water allows the animals living in water such as fishes to survive.

Solubility
Maximum amount of solute that can be dissolved in 100 ml of a solvent is called its solubility. It is expressed in gram/100 ml. Solution is an example of homogeneous mixture.
On the basis of solubility solution can be further divided as:

Unsaturated : A solution that is capable of dissolving more of solute at the given temperature is known as unsaturated solution.

Saturated : A solution which is not capable of dissolving any more of solute at a given temperature is called a saturated solution.

If we add any more solute to a saturated solution of the substance, it remains undissolved and settles as solid at the bottom of the container.

Supersaturated solution : A solution is said to be supersaturated when it contains more of the solute than could be dissolved by the solvent under normal conditions. For example, carbonated water.

Effect of Temperature on Solubility
Solubility increases with increase in temperature. A given amount of solid solute dissolves more quickly in hot solvent than in a cold solvent. For example, sugar dissolves very fast in hot water than in cold water. That is why while preparing lemonade sugar is added before adding ice.

<1M>

1.The process used to separate two immiscible liquids is -
(A) Sedimentation.
(B) Evaporation.
(C) Distillation.
(D) Decantation process.

2.The process of winnowing is based on the principle
(I) Lighter husk particles are carried away by the wind.
(II) Heavy grains fall down in a heap.
(III) Husk and wheat are evincible.
(IV) Wheat grains are blown away by the wind.
Which of above sentences is/are correct?
(A) I only
(B) I and IV
(C) I and II
(D) II and III

3.The paper used in the process of filtration to separate a mixture of sand and water is
(A) Butter paper
(B) Plain paper
(C) Tissue paper
(D) Filter paper

4.The process of conversion of water vapour into its liquid form on cooling is known as -
(A) Evaporation.
(B) Condensation.
(C) Distillation.
(D) Decantation.

5.The method of handpicking is useful when
(I) The impurities are large in quantity.
(II) The impurities are large in size.
(III) The impurities are less in quantity.
(IV) The impurities are smaller in size.
(A) I and II are correct.
(B) II and IV are correct.
(C) II and III are correct.
(D) All are correct.

6.Name the method of separation to obtain clear water from muddy water?

7.The process of ................................is used in the manufacture of salt from sea water.
(A) Condensation
(B) Filtration
(C) Evaporation
(D) Sedimentation

8.The separation of the constituents of a mixture is done to -
(A) Remove harmful and unwanted constituents.
(B) Obtain pure sample of a substance.
(C) Obtain useful constituents.
(D) All are correct.

9.What do you understand by a mixture?

10.Name two materials used as filters.

11.Which property of the constituents of a mixture is used in winnowing.

12.Define Filtration.

13.A mixture of rice and stone particles is separated by
(A) Hand picking
(B) Sieving
(C) Winnowing
(D) Churning

14.The method of sieving is used to separate
(A) Components of same size.
(B) Components of different size.
(C) Soluble impurities.
(D) Liquid impurities.

15.The process of drying the wheat stalks in the sun and then beating them to separate the grains is called
(A) Winnowing
(B) Threshing
(C) Churning
(D) Sieving

16.Which of the following mixtures use filtration as method of separating components?
(i) Salt in water (ii) Tea with tea leaves
(iii) Chalk powder in water (iv) Fruit juice with its pulp
(A) (i), (ii) & (iii)
(B) (ii) & (iii)
(C) (ii), (iii) & (iv)
(D) (i) only

17.Dust particles when mixed with water settle down at the bottom of the container because
(A) They react with water.
(B) They are miscible in water.
(C) They become heavier when water is poured on them.
(D) None of the above.

18.Match the following and choose the answer from the code given below.
(A) Separates stones from sand (i) Filtration
(B) Separates wheat from husk (ii) Winnowing
(C) Separates tea leaves from tea (iii) Churning
(D) Separates butter from curd (iv) Sieving
(A) A- (ii), B-(iii), C-(i), D-(iv)
(B) A- (ii), B-(iv), C-(i), D-(iii)
(C) A- (iii), B-(iv), C-(ii), D-(i)
(D) A- (iv), B-(i), C-(ii), D-(iii)

19.When water changes into vapours, the process is called
(A) Condensation
(B) Heating
(C) Cooling
(D) Evaporation

20.A mixture of salt and water can be separated by this process
(A) Evaporation
(B) Filtration
(C) Sedimentation
(D) Handpicking

21.When a mixture of sugar in water cannot dissolve more of sugar at room temperature, the solution is called
(A) Saturated solution
(B) Unsaturated solution
(C) Super saturated solution
(D) None of the above

22.Condensation is a process when
(A) Aliquid changes into its vapours.
(B) The vapours change into liquid.
(C) Ice melts to form water.
(D) Water freezes to form ice.

23.When muddy water is left undisturbed
(i) The mud settles down.
(ii) Some mud particles remain floating in water.
(iii) The water can be decanted and separated.
(iv) The process of filtration can be used to separate mud particles completely.
Which of the above is correct?
(A) (iii) & (iv)
(B) (i) Only
(C) (i) & (iv)
(D) All the above

24.The process used to separate grains from stalk is
(A) Threshing
(B) Winnowing
(C) Handpicking
(D) Sieving

25.When a glass containing muddy water is left undisturbed and the mud is allowed to settle down, this method is called
(A) Decantation
(B) Filtration
(C) Sedimentation
(D) Evaporation

26.When salt water in a beaker is boiled, the water............ and .................. is left behind
(A) Boils, sand
(B) Evaporates, salt
(C) Evaporates, sand
(D) Vaporizes, nothing

27.The strainer to strain tea from tea leaves acts as a
(A) Filter
(B) Condenser
(C) Boiler
(D) Churner

28.We need to separate the components of a mixture because
(i) Mixtures are useless.
(ii) Non useful components need to be separated from useful ones.
(iii) Impurities and harmful substances need to be removed.
(iv) The components are different and invisible.
(A) (i) only
(B) (ii) & (iii)
(C) (iii) & (iv)
(D) (iv) only

29.Match the items of column 'A' with the items of column 'B':
Column A                                Column B
I. Pulp form fruit juice         (a) Threshing
II. Sieving                           (b) Churning
III. Butter from milk             (c) Husk from wheat
IV. Grains from stalks         (d) filtration
(A) I - b, II- d, III - a, IV - c
(B) I - a, II - c, III - b, IV - d
(C) I - b, II - d, III - c, IV - a
(D) I - d, II - c, III - b, IV - a

30.A _______ is used for separating insoluble solid particles from a liquid.
(A) Piece of muslin cloth.
(B) Filter paper.
(C) Both (1) and (2).
(D) None of these.

31.Salt is obtained from the salt water by the process of-
(A) Magnetic separation.
(B) Decantation.
(C) Evaporation.
(D) None of these.

32.The property which forms the basis of sieving is -
(A) Difference in weight.
(B) Difference in size.
(C) Difference in shape.
(D) Difference in colour.

33.Decantation is used for -
(A) Separating two miscible liquids having different boiling points.
(B) Separating two immiscible liquids.
(C) Both (A) and (B).
(D) None of these.

34.A mixture of sand and dried leaves can be separated by -
(A) Magnetic separation.
(B) Hand picking.
(C) Winnowing.
(D) Sieving.

35.Process used to separate mud from water is-
(A) Evaporation.
(B) Decantation.
(C) Sedimentation.
(D) Both (2) and (3).

36.The process of conversion of a liquid into its vapours is called-
(A) Evaporation.
(B) Filtration.
(C) Sublimation.
(D) Condensation.

37.Find the odd one out -
(A) Chalk powder.
(B) Sand.
(C) Mud.
(D) Sugar.

38.A solid substance is dissolved in water. Which of the following method is used for separating it?
(A) Evaporation.
(B) Decantation.
(C) Filtration.
(D) Sedimentation.

39.The process of settling down of particles of a solid in a liquid is -
(A) Sublimation.
(B) Sedimentation.
(C) Decantation.
(D) Filtration.

40.Various substances present in a mixture are called-
(A) Elements.
(B) Compounds.
(C) Atoms.
(D) Components.

41.A mixture of corn and husk is separated by -
(A) Handpicking.
(B) Winnowing.
(C) Sieving.
(D) Filtration.

42.What is decantation?

43.What is evaporation?

44.What is condensation?

45.Why do we need to separate different substances present in a mixture ?

46.Is it a good practice to sieve flour before consuming it ?

47.Why hand picking method is not used in godowns to remove dirt, stone or husk from the grains of wheat and ricel

48.Which principle is used for separating a mixture of two immiscible liquids.

49.Identify the mixtures from the following : Pickle, Chutney, Jam, Sugar, Water, Common salt.

<2M>

50.Name the method of separation, which is used to obtain salt from seawater. Define that method.

51.What is a saturated solution? How can you dissolve more substance in it?

52.What is sedimentation? Give example.

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

54.How will you separate husk or dirt particles from pulses before cooking ?

55.You are given a mixture of sand and water. How will you separate it ?

56.How will you make the muddy water clear ?

<3M>

57.Why do we need to separate different components of a mixture? Give an example

58.What is sieving? Where is it used?

59.How do we separate salt and sand from their mixture?

60.Explain the process of filtration. Give at least two examples where it is used in our daily life

61.How is salt obtained from sea water?

<5M>

62.What is winnowing? Explain. Where is it used?

63.when do we use the following ?
a) Threshing
b) hand picking
c) filtration
d) sieving
e) sedimentation and decantation

64.Is it possible to separate salt from a solution of salt in water ? If yes, how will you do it ?

65.What is the need for separation of substances?

66.How common salt is obtained from sea water?

67.what is winnowing? Where is it used?