Mastering Separation of Substances: Your Complete Guide and Solved Exercises
Introduction
Welcome back to www.jitudas.com. In this post, we delve deep into the essential science topic: Separation of Substances. In our daily lives, we constantly separate components from mixtures. Whether it's filtering tea leaves, straining rice, or removing impurities from water, understanding the properties that make this possible is key.
This post provides a refined and accurate set of solved exercises to help you master this concept.
EXERCISE: Solved Questions on Separation of Substances
1. Multiple Choice Questions (MCQs)
Darken the circle of the correct answer (provided here for your study).
(i) Which of the following mixtures can be separated by hand picking?
(a) Common salt and sand.
(b) Sawdust and iron filings.
(c) Rice grain and stone. ✓
(d) Camphor and sand.
Ans: (c) Rice grain and stone. This is effective because the stone is large enough and distinctly different from rice to be picked by hand.
(ii) Which method is used when we wash pulses to clean them of dust and fine dirt?
(a) Threshing.
(b) Handpicking.
(c) Sieving.
(d) Decantation. ✓
Ans: (d) Decantation. We add water to the pulses, allowing the heavier particles (pulses) to settle (sedimentation) while the lighter dust/dirt particles float. The dirty water is then poured off (decanted).
(iii) Which method is used for separating a mixture of "iron and coal dust"?
(a) Evaporation.
(b) Threshing.
(c) Magnetic separation. ✓
(d) Decantation.
Ans: (c) Magnetic separation. Iron is a magnetic material, while coal dust is non-magnetic.
(iv) Which method is used to separate tea leaves from tea?
(a) Threshing.
(b) Handpicking.
(c) Sieving.
(d) Filtration. ✓
Ans: (d) Filtration. A tea strainer acts as a filter, separating the liquid (tea) from the larger solid particles (tea leaves).
2. Match the Following
Match the processes in Column A with the correct separating technique in Column B.
| Column A | Column B |
|---|---|
| (a) Separation of mud in water | (vi) Decantation |
| (b) Alum mixed in muddy water | (iv) Filtration (Loading via alum makes filtration efficient) |
| (c) Revolving a mixture at high speed | (v) Churning (or Centrifugation) |
| (d) Groundnut oil and water | (vi) Decantation (Used as the primary method here) |
| (e) Sand and iron filings | (i) Magnetic separation |
| (f) Common salt dissolved in water | (iii) Filtration followed by evaporation (Filters out any suspended solid impurities before evaporation) |
| (g) Husk from paddy seed | (ii) Winnowing |
3. Fill in the Blanks
(a) The Magnetic separation method is used to separate iron filings from a heap of garbage.
(b) Two immiscible liquids can be separated with the help of the Decantation method (or by using a separating funnel).
(c) Flour and bran can be separated by the Sieving method.
(d) The Winnowing method is used to separate wheat from straw.
(e) During filtration of a sand-water mixture, water particles pass through the holes of the filter paper because water particles are Small and soluble, while sand particles are large and insoluble.
4. Answer the Following Questions
(a) How will you separate a mixture of salt and sand?
Ans: To separate salt and sand, add water to the mixture. The salt will dissolve in the water, while the sand remains as an insoluble residue. Filter the mixture. The sand will collect as the residue on the filter paper. Collect the filtrate (salt solution) and evaporate it by boiling. The water will evaporate, leaving the salt in the container.
(b) Suggest a method to separate a mixture of coconut oil and water.
Ans: The Decantation method is used to separate a mixture of coconut oil and water. Because they are immiscible liquids of different densities, they will form two distinct layers when left undisturbed. The lighter oil will float on the water and can be carefully poured (decanted) off.
(c) How will you separate salt from salt solution?
Ans: Salt can be separated from a salt solution by Evaporation. Boil the salt water until all the water evaporates. The salt will remain in the container.
5. In the following mixtures, which property can be used for the separation of their components?
| Mixture | Property / Method Used |
|---|---|
| (a) Salt and chalk powder | Solubility (Salt dissolves in water; chalk powder does not). Method: Dissolution -> Filtration -> Evaporation. |
| (b) Rice and straw | Difference in weight (Straw is lighter). Method: Winnowing. |
| (c) Chalk and coal | Difference in physical appearance (color, shape). Method: Handpicking. |
| (d) Iron filings and sawdust | Magnetic Property (Iron is magnetic). Method: Magnetic separation. |
| (e) Sand and rice grain | Difference in size. Method: Sieving. |
6. How do we obtain salt from seawater?**
Ans: Salt is primarily extracted from seawater. Seawater contains a significant amount of common salt, along with other substances. To obtain it, seawater is allowed to stand in large, shallow pits. Under the heat of the sun, the water slowly evaporates. After a few days, the water evaporates completely, leaving behind solid salt mixed with other impurities. The common salt is then purified from this mixture through a process called purification to make it fit for consumption.
7. What is the criterion for the selection of methods to separate the components from a mixture?
Ans: The selection of a separation method is primarily based on the differences in physical properties of the components of the mixture. These key properties include:
- Size: Used in sieving or handpicking.
- Shape and Color: Used in handpicking.
- Weight (Density): Used in winnowing, sedimentation, and decantation.
- Magnetic property: Used in magnetic separation.
- Solubility (in liquids like water): Used in filtration and evaporation.
- State of matter: Determining if components are solid, liquid, or gas.
8. Write all the possible methods used to purify muddy river water to obtain clear water.
Ans: The following methods are used in sequence to purify muddy river water:
(i) Sedimentation: Letting the water stand undisturbed, allowing the heavy mud and sand particles to settle to the bottom.
(ii) Decantation: Carefully pouring off the clearer water from the top, leaving the settled mud behind.
(iii) Filtration: Passing the decanted water through a filter (like filter paper or sand beds) to remove any remaining fine suspended particles.
(iv) Boiling: Heating the filtered water to kill harmful microorganisms.
(v) Chlorination: Adding chlorine tablets or solutions to disinfect the water by killing pathogens.
9. Explain filtration with the help of a diagram.
(Include an illustrative diagram of Filtration here on your blog)
Ans: Filtration is a physical process used to separate insoluble solid particles from a liquid or gaseous mixture by passing it through a medium, known as a filter.
The filter has tiny pores that allow the liquid (solvent or filtrate) to pass through, but are too small to allow the solid particles (residue) to pass. The solid residue is trapped on the filter medium, while the clear liquid passes into the collecting container (the filtrate). Common filter media include filter paper, fine cloth, and sand beds.
10. In activity 6.2 in this chapter, name the method of separation applicable for all the possible mixtures listed.
Below is the completed table of potential mixtures and their separation methods.
| S.I No. | Two substances taken | Their physical state | Soluble/ insoluble | Method of Separation |
|---|---|---|---|---|
| 1 | Salt, Water | Solid, liquid | Soluble | Evaporation |
| 2 | Oil, Water | Liquid, liquid | Insoluble | Decantation |
| 3 | Sand, Water | Solid, Liquid | Insoluble | Sedimentation -> Filtration |
Additional Question Closely Relevant to This Post
Question: Explain the concept of 'Loading' in the context of purifying muddy water, and state which substance is commonly used for this purpose.
Ans: Loading is a speed-up process of sedimentation. When muddy water contains very fine suspended clay or mud particles that take a very long time to settle, loading is used.
This is done by dissolving a piece of Alum (Fitkari) in the muddy water. The alum particles attach themselves to the fine clay particles, making them heavier. Due to this increased weight, the fine particles settle down quickly, significantly speeding up the clarification process. The clear water can then be separated by decantation or filtration.
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