5. Separation of substances WORKBOOK ANSWER
1. Choose the correct option.
a) Which of the following is an example of a gas-liquid mixture?
i) Sugar syrup ii) Lime water
iii) Soda water iv) Sea water
ans: Soda water
b) ____________ method cannot be used to separate solid-solid mixtures. (a) Handpicking (b) Sieving
(c) Winnowing (d) Evaporation
ans: Evaporation
c) Fine particles of sand in river water are removed by the process of ____________. (a) decantation (b) filtration
(c) evaporation (d) sedimentation
ans: filtration
2. Name the following:
a) The process of settling down of heavier insoluble particles at the bottom of a liquid.
ans: Sedimentation
b) The process of conversion of water vapour into its liquid form, on cooling. ans: Condensation
c) The method used to separate grains from their stalks.
ans: Threshing
d) A clear liquid obtained by the process of filtration.
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ans: Filtrate
3. State whether the following statements are true or false. Correct the false statements.
a) Cobalt and nickel are magnetic materials.
ans: True
b) Solubility of a solute decreases with increase in temperature.
ans: False
Solubility of a solute increases with increase in temperature.
c) A substance in which solute dissolves is known as a solvent.
ans: True
d) The constituents of all mixtures can be seen separately.
ans: False
The constituents of heterogeneous mixtures can be seen separately.
4. Assertion-reasoning type questions
In the following questions, two statements are given- one labelled Assertion (A) and the other labelled Reason (R). Read the statements carefully and choose the correct alternative (A), (B), (C) and (D) as given below.
(A) Both A and R are true and R is correct explanation of the assertion. (B) Both A and R are true but R is not the correct explanation of the assertion. (C) A is true but R is false.
(D) A is false but R is true.
a) Assertion: Water is a universal solvent.
Reason: Water dissolves the nutrients in soil and carries it to all parts of the plants.
ans: (B) Both A and R are true but R is not the correct explanation of the assertion.
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b) Assertion: A magnet is used to separate a mixture of iron fillings from sand. Reason: Iron is a magnetic material and sand is a non-magnetic material. ans: (A)Both A and R are true and R is correct explanation of the assertion.
5. Define the following:
a) Decantation
ans: The process of pouring out a clear liquid from a vessel (after sedimentation) without disturbing the sediment is called decantation.
b) Winnowing
ans: The method of separating heavier and lighter components of a mixture by wind or blowing air is called winnowing.
6. Answer the following in brief.
a) What are immiscible liquids? Give an example of immiscible liquids. ans: Liquids that do not mix with each other are called immiscible liquids. Mixture of oil and water are examples of immiscible liquids.
(examples may vary accept all correct responses)
b) How is a homogeneous mixture different from a heterogeneous mixture? ans: A homogeneous mixture has a uniform composition and its components cannot be seen separately whereas; a heterogeneous mixture does not have a uniform composition and its components can be seen separately.
c) What is solubility? List the factors affecting the solubility of a substance. ans: The amount of solute that can be dissolved in a solvent is known as the solubility of that solvent.
Factors affecting solubility:
∙ Heating
∙ Stirring
∙ Size of solute particles
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7. Give reasons for the following statements.
a) Water droplets are seen on the outer surface of a glass filled with ice cold water.
ans: This is because of the condensation of water vapours present in the atmosphere.
b) Powdered sugar dissolves faster in water than table sugar.
ans: This is because solubility increases on using powdered solute.
8.
a) Identify and explain the process shown in the diagram.
ans: Evaporation
The conversion of a liquid into its gaseous state is known as evaporation.
b) Give an example of a mixture that can be separated by this method. ans: Salt and water/ sugar and water
9. Observe your daily life and list activities that involve the processes of evaporation and condensation. (list at least two activities for each process)
ans:
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(answers may vary accept all relevant examples)
10. Identify the word from the given clues:
a) A shallow vessel with small holes at the bottom used to separate wheat bran from flour.
ans: Sieve
b) A special type of paper with small pores that is used to separate sand from water. ans: Filter paper
HOTS
11. Why do we feel cool on sweating on a hot summer day?
ans: We feel cool on sweating on a hot summer day because sweat absorbs extra heat from our body and gets evaporated.
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