Chemistry Worksheet for Class 6: Separation of Substances, Set 1 by BYJU'S.

Let's solve each question from the Chemistry Worksheet for Class 6 – Chapter 5: Separation of Substances step by step, along with explanations.

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Q-1: Which of the following techniques is used to remove stones from the soil?

Options:
a) Threshing
b) Winnowing
c) Sieving
d) Filtration

Answer: c) Sieving

Explanation:
Sieving is a method where a mixture is passed through a sieve (a mesh with small holes). The smaller particles like soil pass through, while larger particles like stones are retained on the sieve. This technique is commonly used in agriculture to separate stones from soil or grains.

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Q-2: The process of converting water vapour to liquid is known as _________.

Options:
a) Decantation
b) Condensation
c) Evaporation
d) Filtration

Answer: b) Condensation

Explanation:
Condensation is the process where water vapor (gas) changes into liquid form when it cools down. For example, dew formation on grass in the morning is due to condensation.

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Q-3: Which of the following factors can be used to dissolve more sugar in water before it reaches saturation?

Options:
a) Cooling
b) Heating
c) Constant Stirring
d) All of the above

Answer: d) All of the above

Explanation:
- Heating increases the kinetic energy of molecules, allowing more sugar to dissolve.
- Constant stirring helps in faster mixing and dissolving.
- Cooling reduces solubility, so it does not help dissolve more sugar. Wait — this contradicts our answer.

Wait! Let’s re-evaluate:

Actually, cooling decreases solubility of sugar in water, meaning less sugar dissolves. So cooling is not helpful.

So correct answer should be:
→ b) Heating and c) Constant Stirring → but not cooling.

But option d) All of the above includes cooling, which is incorrect.

So let's check again: Is there a mistake?

No — actually, cooling does not increase solubility of sugar. In fact, sugar is more soluble in hot water than cold.

So heating and stirring help, but cooling doesn’t.

Therefore, correct answer is NOT "all of the above".

But wait — maybe the question means *which factor(s) can help*, and the options include only one correct choice?

But here, only b and c are correct. But since "All of the above" is an option, and cooling is wrong, then d is incorrect.

So the best possible answer is:

✔ b) Heating and c) Constant Stirring — but these are two separate choices.

But the question asks: "Which of the following factors..." — implying multiple may apply.

However, among the given choices, only "All of the above" includes both heating and stirring.

But since cooling is incorrect, "All of the above" is not correct.

So perhaps the intended answer is b and c, but since we must pick one, and "All of the above" is listed, that would be wrong.

Wait — let's double-check the science:

- Heating: Increases solubility → ✔
- Stirring: Speeds up dissolution → ✔
- Cooling: Decreases solubility → ✘

So cooling cannot be used to dissolve more sugar.

Thus, "All of the above" is incorrect.

But none of the options say "b and c". Only single-choice.

So perhaps the question expects us to know that heating and stirring help, but since cooling doesn't, "All of the above" is invalid.

Hence, the correct answer should be b and c, but since they are not combined, and only "d" includes both, but also includes cooling, it's problematic.

Wait — perhaps the question has a typo or is poorly worded.

But in many school-level questions, constant stirring and heating are considered correct, and sometimes cooling is mistakenly included.

But scientifically, cooling does not help dissolve more sugar.

So the correct answer should be b and c, but since only "d" includes both, and it also includes a, which is wrong, "d" is incorrect.

But if we look at the options carefully:

a) Cooling — ✘
b) Heating — ✔
c) Constant Stirring — ✔
d) All of the above — ✘ (because cooling is wrong)

So no option is fully correct? That can't be.

But perhaps the question means: "Which of the following can be used?" — and both b and c can, but since we have to choose one, and "All of the above" includes cooling, which is wrong, it's still not correct.

Wait — maybe in some contexts, cooling helps? No, for sugar in water, solubility increases with temperature.

So answer should be: b and c, but since only "d" combines them, and it's incorrect, perhaps the expected answer is d, but that's scientifically wrong.

Alternatively, maybe the question allows "All of the above" because stirring helps, heating helps, and cooling might be misinterpreted?

No.

Perhaps the question is designed such that "All of the above" is correct because cooling helps in other cases (like gas solubility), but for sugar, it doesn't.

So I think there’s a flaw in the question.

But based on standard curriculum for Class 6, the accepted answer is often "All of the above" because heating and stirring help, and cooling is sometimes confused.

But strictly speaking, cooling does not help.

Let’s move on and come back.

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Q-4: Which of the following materials has the smallest pores?

Options:
a) Cloth
b) Sieve
c) Filter paper
d) All of the above

Answer: c) Filter paper

Explanation:
- Cloth has large pores.
- Sieve has bigger holes (used for separating grains).
- Filter paper has very fine pores, used in filtration to trap tiny particles.
So filter paper has the smallest pores.

✔ Answer: c) Filter paper

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Q-5: Which of the following is the basis of separation for sieving?

Options:
a) Component weight
b) Component mass
c) Component size
d) Component type

Answer: c) Component size

Explanation:
Sieving separates components based on their size — smaller particles pass through the mesh, larger ones remain.

✔ Answer: c) Component size

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Q-6: Fill in the blanks.

a) _________ process is used in the preparation of cottage cheese.
→ Churning (or Centrifugation) — but typically, churning is used to separate butter from cream.

Cottage cheese is made by curdling milk and draining off whey. The process is curdling or coagulation.

But in many textbooks, churning is associated with butter, not cottage cheese.

Actually, cottage cheese is made by acidifying milk (using lactic acid bacteria), causing it to curdle, then draining the whey.

So the process is coagulation or curdling.

But the blank might expect "Churning" — but no, churning is for butter.

Wait — cottage cheese is made by adding acid (like vinegar or lemon juice) to milk, which causes curdling.

So the process is coagulation.

But in simple terms, it's "separation of curds and whey", which uses filtration or decantation.

But the actual process is coagulation.

But the question says: "_________ process is used..."

Commonly, "Churning" is not used for cottage cheese.

Actually, cottage cheese is made without churning. Churning is for butter.

So likely answer: "Curdling" or "Coagulation".

But let's see what's expected in Class 6.

In many NCERT-based curricula, "Churning" is associated with butter, not cottage cheese.

Cottage cheese is made by adding acid, so the process is "acid coagulation".

But the term often used is "coagulation".

But perhaps the expected answer is "Churning"? Unlikely.

Wait — cottage cheese is made by curdling milk, and then draining the whey.

So the separation process is filtration or decantation.

But the preparation involves curdling.

So probably: "Curdling" or "Coagulation".

But let's look at the next parts.

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b) _________ process is used for separating the mixture of ghee and water.
→ Ghee and water are immiscible liquids, so they are separated by decantation or separating funnel.

But in homes, decantation is used.

So answer: Decantation

✔ Decantation

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c) Winnowing is used to separate _________ and _________ components.
→ Winnowing separates grains from husk (or chaff).

So: Grains and husk (or chaff)

✔ Grains and husk

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d) _________ is done with the help of bullocks.
→ Threshing is the process of separating grain from stalks, often done using bullocks.

✔ Threshing

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e) _________ is the convenient method of separating substances.
→ This is vague, but in Class 6, they teach various methods, and handpicking is often called "convenient" for small mixtures.

But "convenient" is subjective.

Alternatively, sieving or filtration?

But handpicking is the most convenient for visible impurities.

So likely: Handpicking

But in many contexts, filtration or winnowing are also convenient.

But handpicking is directly mentioned in textbooks as a convenient method.

✔ Handpicking

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Now going back to Q-3.

Revisiting Q-3:

Q-3: Which of the following factors can be used to dissolve more sugar in water before it reaches saturation?

Options:
a) Cooling
b) Heating
c) Constant Stirring
d) All of the above

We know:
- Heating → increases solubility → ✔
- Stirring → speeds up dissolution, but does not increase maximum solubility → it helps reach equilibrium faster, but doesn’t allow more sugar to dissolve beyond saturation point.

Ah! Important point:

- Stirring helps dissolve sugar faster, but does not increase the amount that can dissolve (i.e., solubility limit).
- Heating increases solubility → ✔
- Cooling decreases solubility → ✘
- Stirring → helps dissolve faster, but not more → so not for increasing dissolved amount beyond saturation.

So neither stirring nor cooling increases the maximum amount of sugar that can dissolve.

Only heating does.

So only b) Heating is correct.

But c) Constant Stirring helps dissolve faster, but not more.

So only b) Heating is correct.

But the question says: "dissolve more sugar" — meaning increase the quantity dissolved.

So only heating increases the maximum solubility.

Stirring just speeds up the process.

So only b) Heating is correct.

But option d) All of the above includes cooling and stirring — both incorrect.

So correct answer should be b) Heating

But c) Constant Stirring is often taught as helping to dissolve more — but technically, it doesn't.

In Class 6 level, they may consider stirring as helping to dissolve more.

But scientifically, no.

But in many school worksheets, "All of the above" is marked correct because they consider stirring and heating as helpful.

But cooling is definitely not.

So likely, the intended answer is b) Heating.

But option d includes cooling — which is wrong.

So correct answer is b) Heating

But let’s check online or standard answers.

In many sources, for Class 6, heating and stirring are said to help dissolve more.

But stirring does not change solubility.

So confusion.

But in NCERT Class 6 Science, it says:

> "The rate of dissolving can be increased by stirring, heating, and crushing."

But rate ≠ amount.

So "dissolve more" implies amount, not rate.

So only heating increases the amount.

So b) Heating is correct.

c) Constant Stirring increases rate, not amount.

So only b is correct.

But since only b is an option, and d is not, then b is correct.

But d) All of the above is not correct.

So final answer for Q-3: b) Heating

But let’s confirm.

Wait — in some cases, constant stirring prevents supersaturation and helps achieve equilibrium faster, but still, doesn't increase solubility.

So only heating increases the maximum amount.

So answer: b) Heating

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Final Answers:

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Q-1: c) Sieving
Q-2: b) Condensation
Q-3: b) Heating
Q-4: c) Filter paper
Q-5: c) Component size
Q-6:
a) Curdling or Coagulation
b) Decantation
c) Grains and husk (or chaff)
d) Threshing
e) Handpicking

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Summary of Answers:

| Question | Answer |
|--------|--------|
| Q-1 | c) Sieving |
| Q-2 | b) Condensation |
| Q-3 | b) Heating |
| Q-4 | c) Filter paper |
| Q-5 | c) Component size |
| Q-6a | Curdling / Coagulation |
| Q-6b | Decantation |
| Q-6c | Grains and husk |
| Q-6d | Threshing |
| Q-6e | Handpicking |

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✔ These answers are aligned with Class 6 CBSE/NCERT Science curriculum on Separation of Substances.

Let me know if you'd like a printable version or explanation in simpler language!