Class 6 Science-Workbook Chapter 5

Class VI 

Chapter 5

Separation of Substances

(Workbook)

I Answer the following questions in brief:

Q.1. Why are stalks of crops dried in the sun before threshing?

Ans - In order to separate the grain from the stalks, they must be dried in the sunlight.

Q.2. When winnowing is a suitable method of separating substances?

Ans - Winnowing is a suitable method for separating substances when we separate the heavy and light components of a mixture by wind or blowing air. 

Q.3. Is husk separated from grains by winnowing of any use to the farmers? If so, what is its use?

Ans - Yes husk is separated from grains by winnowing. It is used to separate the heavier and lighter components of the mixture by blowing air.

Q.4. Name the process that can be used to separate mustard oil and water from their mixture?

Ans - Decantation is the process that can be used to separate mustard oil and water from their mixture.

Q. 5 Which quality of filter paper makes it suitable for separating components of a mixture?

Ans - Filter paper is a semi-permeable paper barrier that separates liquids or air from one another. It is used to separate fine solid particles from liquids or gases.

Q. 6 What is the main shortcoming of using evaporation without condensation for separating components of a mixture?

Ans - We can Separate the mixture like ink from water and salt from water.

Q.7. Can we add more of the dissolved substance in a saturated solution? If yes, how?

Ans - Yes we add more of the dissolved substances in a saturated solution by increasing the temperature of a solution.

Q.8. Justify: Every solution is a mixture but not every mixture is a solution.

Ans - In a solution, two substances dissolve permanently into one another to produce a single phase. While the mixture is a combination of two or more substances. A mixture of oil cannot be said to be a solution because it is not homogeneous.

Q.9. How is salt obtained from sea water?

Ans - Salt is obtained from seawater by the process of evaporation. The seawater evaporates due to the sun's heat and solid salt is left behind. The left salt is collected and refined to get purified salt.

Q. 10 Which property of alum is used to purify water by loading?

Ans - Alums are highly soluble in water. When alum is added to impure water, heavy particles of dissolved alum deposit on the suspended clay particles in water. In this way, water gets loaded with alum and becomes heavy and settles down at the bottom. This step is called loading. It thus removes the suspended clay particles from water.

II Give one term for each of the following:

(a) Settling down of heavier component in mixture Sedimentation.

(b) Stirring a mixture forcefully to separate its components. Churning. 

(c) A solution in which no more of a substance can be dissolve. Saturated Solution.

(d) Process of conversion of water vapour into liquid from Condensation.

(e) Settling down of mud in its mixture with water with help of alum Loading.

(f) Separating components of a mixture by using wind. Winnowing.

III Fill in the blanks:

(a) When pure wheat flour is sieved, bran remains in the sieve.

(b) More of a substance can be dissolved in a saturated solution by heat it.

(c) Evaporation is a Conversion of water into Vapour process.

(d) The substances to be separated may be particles of different sizes or materials.

(e) An alum is dipped into muddy water for loading of impurities.

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

IV State whether True or False:

(a) The process of decantation can be used for separating lemon juice from lemonade.  (False) 

(b) When the process of evaporation is applied to sea water we obtain a mixture. (True)

(c) Filtration is useful for separating components having very different particle sizes. (False)

(d) We cannot dissolve any more of a substance in a saturated solution under any condition. (True)

(e) A mixture of powdered salt and powdered sugar can be separated by the process of winnowing. (False)

(f) More than one methods can be employed to separate the components of a mixture. (True)

V. Match the following:

Ans  a)  vii) Evaporation

b)  ii) Hand picking

c)  vi) None of the studied method

d)  iii) Winnowing

e)  i) Sedimentation and decantation

f)  v) Sieving

VI. Choose the correct alternative:

 i) Liquids that do not mix with each other can be separated by using

Ans  (c) Decantation

ii) When the component of a mixture are separated, which of the following is true?

Ans (d) None of the above

iii) Muddy water can be purified by using 

Ans (d) All of these

iv) More of a substance can be dissolved in a saturated solution by 

Ans (a) Heating

v)  For using the method of winnowing, the particles of the components should be 

Ans (b) Different is weight

vi) Nyasa was given a mixture of salt with fine sand with fine sand particles. She employed the method represented in the diagrams given below (the diagrams may not be in order)

Ans (c) Y,X,Z

H.W.  

VII - Complete the following word puzzle with the help of the clues given below: