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Methods of Separation in Everyday Life – CBSE NCERT Study Resources

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Methods of Separation in Everyday Life

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6th

6th - Science (EVS) Curiosity

Methods of Separation in Everyday Life

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Overview of the Chapter

This chapter explores the various methods used to separate mixtures in everyday life. Students will learn about different techniques such as handpicking, sieving, winnowing, sedimentation, decantation, filtration, evaporation, and condensation. These methods are essential for understanding how substances can be purified or isolated for practical use.

Methods of Separation

Handpicking

Handpicking is a simple method used to separate larger impurities like stones or husk from grains or pulses. It is done manually and is effective when the impurities are visibly different from the desired substance.

Definition: Handpicking involves manually removing unwanted substances from a mixture based on visible differences.

Sieving

Sieving is used to separate components of a mixture based on differences in particle size. A sieve with small holes allows smaller particles to pass through while retaining larger particles.

Definition: Sieving is the process of separating fine particles from coarse ones using a mesh or sieve.

Winnowing

Winnowing is a traditional method used to separate lighter husk particles from heavier grains. The mixture is dropped from a height, and the wind blows away the lighter husk while the grains fall straight down.

Definition: Winnowing separates lighter and heavier components of a mixture using wind or air.

Sedimentation and Decantation

Sedimentation involves allowing heavier particles in a liquid mixture to settle at the bottom. Decantation is then used to pour out the clear liquid without disturbing the settled particles.

Definition: Sedimentation is the process of settling down of heavier particles in a liquid, while decantation involves pouring out the clear liquid after sedimentation.

Filtration

Filtration is used to separate insoluble solids from liquids by passing the mixture through a filter paper or cloth. The solid particles are retained on the filter, while the liquid passes through.

Definition: Filtration is the process of separating insoluble solids from liquids using a filter medium.

Evaporation and Condensation

Evaporation is used to separate a soluble solid from a liquid by heating the mixture until the liquid turns into vapor, leaving the solid behind. Condensation is the reverse process where vapor is cooled to form a liquid.

Definition: Evaporation is the conversion of a liquid into vapor, while condensation is the conversion of vapor back into a liquid.

Applications in Everyday Life

These separation methods are widely used in daily activities such as cooking, cleaning, and water purification. For example, filtration is used in water purifiers, while evaporation is used in making salt from seawater.

All Question Types with Solutions – CBSE Exam Pattern

Explore a complete set of CBSE-style questions with detailed solutions, categorized by marks and question types. Ideal for exam preparation, revision and practice.

Very Short Answer (1 Mark) – with Solutions (CBSE Pattern)

These are 1-mark questions requiring direct, concise answers. Ideal for quick recall and concept clarity.

Question 1:
Name the method used to separate tea leaves from tea.
Answer:
Filtration
Strainer or sieve
Question 2:
How can we separate salt from seawater?
Answer:
Evaporation
Boiling the water
Question 3:
What method separates husk from wheat flour?
Answer:
Sieving
Using a fine sieve
Question 4:
Which process separates butter from milk?
Answer:
Centrifugation
Spinning at high speed
Question 5:
How is sand separated from water at home?
Answer:
Sedimentation
Letting it settle down
Question 6:
Name the method to separate iron nails from sand.
Answer:
Magnetic separation
Using a magnet
Question 7:
How do we separate oil from water?
Answer:
Decantation
Pouring oil carefully
Question 8:
What method separates stones from rice?
Answer:
Handpicking
Removing by hand
Question 9:
How is muddy water cleaned?
Answer:
Filtration
Using a cloth filter
Question 10:
Which method separates chalk powder from water?
Answer:
Filtration
Using filter paper
Question 11:
How do we separate lentils from pebbles?
Answer:
Handpicking
Picking them manually
Question 12:
Name the process to obtain salt crystals from brine.
Answer:
Crystallization
Evaporating the water
Question 13:
How is cream separated from milk?
Answer:
Churning
Stirring vigorously
Question 14:
What method separates dyes in ink?
Answer:
Chromatography
Using filter paper
Question 15:
Name the method used to separate tea leaves from prepared tea.
Answer:

The method used is filtration. A strainer or filter paper can separate the tea leaves from the liquid tea.

Question 16:
What is the principle behind winnowing?
Answer:

Winnowing works on the principle of difference in weight. Lighter particles like husk are blown away by wind, while heavier grains fall down.

Question 17:
How can you separate a mixture of salt and sand?
Answer:

Dissolve salt in water, then filter to remove sand.
Evaporate the water to recover salt.

Question 18:
Why is handpicking useful for separating larger impurities?
Answer:

Handpicking is simple and effective for removing visible, larger impurities like stones from grains.

Question 19:
What property allows sieving to separate mixtures?
Answer:

Sieving uses difference in particle size. Smaller particles pass through the sieve, while larger ones remain.

Question 20:
Give an example where sedimentation and decantation are used.
Answer:

Separating mud from water. Mud settles (sedimentation), and clear water is poured out (decantation).

Question 21:
How does threshing help in farming?
Answer:

Threshing separates grains from stalks by beating or crushing, making harvesting easier.

Question 22:
Why is evaporation used to recover salt from seawater?
Answer:

Seawater has dissolved salt. Evaporation removes water, leaving solid salt behind.

Question 23:
Name a mixture where magnetic separation is applicable.
Answer:

Separating iron nails from sand using a magnet.

Question 24:
What is the purpose of churning in butter preparation?
Answer:

Churning separates butterfat from liquid buttermilk by agitating cream.

Question 25:
How does filtration purify water at home?
Answer:

A water filter traps impurities like dirt, letting clean water pass through.

Question 26:
Why is sieving preferred over handpicking for flour?
Answer:

Sieving is faster and more efficient for fine particles like flour, removing lumps or impurities.

Very Short Answer (2 Marks) – with Solutions (CBSE Pattern)

These 2-mark questions test key concepts in a brief format. Answers are expected to be accurate and slightly descriptive.

Question 1:
What is sedimentation? Give one example from daily life.
Answer:

Sedimentation is the process where heavier solid particles settle down at the bottom of a liquid when left undisturbed.
Example: Mud settling in a bucket of muddy water.

Question 2:
Why is filtration used to separate tea leaves from tea?
Answer:

Filtration separates insoluble solids (like tea leaves) from liquids (tea) using a filter medium (strainer).
It ensures clear tea without solid residues.

Question 3:
Name the method used to separate cream from milk. Explain briefly.
Answer:

Centrifugation is used.
It spins milk at high speed, forcing denser milk to the bottom and lighter cream to the top.

Question 4:
How does winnowing help farmers separate grains from husk?
Answer:

Winnowing uses wind to blow away lighter husk, while heavier grains fall straight down.
Commonly used for crops like wheat.

Question 5:
What is the principle behind evaporation as a separation method?
Answer:

Evaporation uses heat to convert liquid (like water) into vapor, leaving behind dissolved solids (e.g., salt from seawater).

Question 6:
How would you separate a mixture of sand and salt?
Answer:

  1. Dissolve salt in water (sand remains insoluble).
  2. Filter to remove sand.
  3. Evaporate water to recover salt.

Question 7:
Why is handpicking suitable for separating pebbles from rice?
Answer:

Handpicking works when impurities (pebbles) are large and visibly different from rice grains.
It’s a simple, manual method.

Question 8:
Describe how sieving separates flour from bran.
Answer:

A sieve has tiny holes that allow finer flour to pass through, while larger bran particles stay behind.

Question 9:
What happens during decantation? Give an example.
Answer:

Decantation pours out a liquid (like water) after sedimentation, leaving sediments behind.
Example: Separating oil from water after settling.

Question 10:
How can you separate iron nails from sawdust? Name the method.
Answer:

Use magnetic separation.
A magnet attracts iron nails, leaving non-magnetic sawdust behind.

Question 11:
Why is threshing done before winnowing?
Answer:

Threshing loosens grains from stalks, making it easier to separate them via winnowing.
Example: Beating wheat stalks to free grains.

Short Answer (3 Marks) – with Solutions (CBSE Pattern)

These 3-mark questions require brief explanations and help assess understanding and application of concepts.

Question 1:
Explain how sieving is used to separate mixtures in everyday life with an example.
Answer:

Sieving is a method used to separate solid mixtures based on particle size. A sieve has tiny holes that allow smaller particles to pass through while retaining larger ones.


Example: At home, we use a sieve to separate fine flour from lumps or impurities. The fine flour passes through the holes, while larger particles remain on top.


Application: It is also used in construction to separate sand from gravel.

Question 2:
Describe the process of sedimentation and decantation with a real-life example.
Answer:

Sedimentation is the process where heavier particles in a liquid settle down at the bottom due to gravity. Decantation involves pouring out the clear liquid without disturbing the settled particles.


Example: Cleaning muddy water by letting the mud settle and then carefully pouring the clean water into another container.


Application: This method is used in water treatment plants to purify water.

Question 3:
How does filtration help in separating mixtures? Give an example.
Answer:

Filtration is a method where a filter (like filter paper or cloth) is used to separate insoluble solids from liquids.


Example: Making tea involves filtering tea leaves from the liquid using a strainer.


Application: It is also used in laboratories to separate precipitates from solutions.

Question 4:
Explain how evaporation can be used to separate salt from seawater.
Answer:

Evaporation is the process where a liquid turns into vapor, leaving behind dissolved solids.


Steps:
1. Seawater is collected in shallow ponds.
2. Sunlight heats the water, causing it to evaporate.
3. Salt remains as solid crystals after all water evaporates.


Application: This method is used in salt pans to produce common salt.

Question 5:
What is handpicking? Give an example where this method is useful.
Answer:

Handpicking is the simplest method of separation where unwanted substances are removed manually from a mixture.


Example: Removing stones or insects from rice before cooking.


Application: It is used when the particles are large enough to be seen and picked easily.

Question 6:
How does winnowing help farmers separate grains from husk? Explain the process.
Answer:

Winnowing is a method where lighter husk is separated from heavier grains using wind.


Steps:
1. The mixture of grains and husk is dropped from a height.
2. Wind blows away the lighter husk.
3. Heavier grains fall straight down and are collected.


Application: Farmers use this method after threshing to clean grains like wheat and rice.

Question 7:
Explain the process of sedimentation and decantation with an example from daily life.
Answer:

Sedimentation is the process where heavier particles in a mixture settle down at the bottom when left undisturbed. Decantation is pouring out the clear liquid without disturbing the settled particles.

Example: Separating mud from water.
1. Allow muddy water to stand still.
2. Mud particles settle down due to gravity (sedimentation).
3. Carefully pour the clear water into another container (decantation).

Question 8:
How is filtration different from sieving? Give one example of each.
Answer:

Filtration separates tiny insoluble solids from liquids using a filter paper, while sieving separates larger solids of different sizes using a sieve.

  • Example of filtration: Removing tea leaves from tea using a strainer.
  • Example of sieving: Separating flour from lumps using a flour sieve.
Question 9:
Describe how evaporation helps in separating salt from seawater.
Answer:

Evaporation is the process where a liquid turns into vapor, leaving behind dissolved solids.

Steps to separate salt:
1. Collect seawater in a shallow container.
2. Place it under sunlight for days.
3. Water evaporates, leaving behind salt crystals.

This method is used in salt pans for large-scale production.

Question 10:
Why is winnowing used by farmers? Explain the process.
Answer:

Winnowing separates lighter husk from heavier grains using wind.

Process:
1. Farmers drop the mixture from a height.
2. Wind blows away the lighter husk.
3. Heavier grains fall straight down.

This is cost-effective and doesn’t require machines, making it ideal for small-scale farming.

Question 11:
What is magnetic separation? Give a real-life application.
Answer:

Magnetic separation uses magnets to separate magnetic materials from non-magnetic ones.

Example: Separating iron nails from sand.
1. Move a magnet through the mixture.
2. Iron nails stick to the magnet.
3. Sand remains behind.

Used in recycling plants to separate metals from waste.

Question 12:
How does handpicking work as a separation method? When is it most useful?
Answer:

Handpicking involves manually removing unwanted components from a mixture.

Useful when:
1. Components are large enough to see.
2. Quantity is small.
3. Other methods are impractical.

Example: Removing stones from rice before cooking.

Long Answer (5 Marks) – with Solutions (CBSE Pattern)

These 5-mark questions are descriptive and require detailed, structured answers with proper explanation and examples.

Question 1:
Explain how sedimentation and decantation are used to separate mixtures in daily life. Give examples.
Answer:
Concept Overview

Sedimentation and decantation are methods to separate insoluble solids from liquids. We studied that heavier particles settle down due to gravity.

Process Explanation
  • First, let the mixture stand undisturbed.
  • Solid particles settle at the bottom (sedimentation).
  • Carefully pour out the clear liquid (decantation).
Real-world Application

Our textbook shows how muddy water is cleaned this way. At home, we separate rice from water after washing using decantation.

Question 2:
Describe filtration with a diagram. How is it different from sieving?
Answer:
Concept Overview

Filtration separates insoluble solids from liquids using a filter. Sieving separates solids of different sizes.

Process Explanation
  • Pour mixture through filter paper/fine cloth.
  • Liquid passes through, solids remain.
[Diagram: Funnel with filter paper separating sand and water]Real-world Application

We filter tea leaves from prepared tea. Sieving is used to separate flour from lumps, unlike filtration which works for solid-liquid mixtures.

Question 3:
How does evaporation help in obtaining salt from seawater? Explain the process.
Answer:
Concept Overview

Evaporation separates dissolved solids from liquids by vaporizing the solvent. We studied this in salt production.

Process Explanation
  • Seawater is collected in shallow ponds.
  • Sunlight evaporates water over days.
  • Salt crystals remain behind.
Real-world Application

Our textbook mentions salt pans in Gujarat. At home, we see evaporation when salt deposits form on sweaty clothes after drying.

Question 4:
Compare hand-picking and winnowing with suitable examples from daily life.
Answer:
Concept Overview

Both methods separate solids, but hand-picking uses manual separation while winnowing uses wind.

Process Explanation
  • Hand-picking: Removing stones from rice grain by grain.
  • Winnowing: Tossing grain mixture to let wind blow away husk.
Real-world Application

We pick out spoiled fruits from baskets. Farmers winnow wheat as shown in our NCERT chapter. Hand-picking works for larger impurities.

Question 5:
Explain how magnetic separation works. Where do we use this method at home?
Answer:
Concept Overview

Magnetic separation divides magnetic materials from non-magnetic ones using magnets.

Process Explanation
  • Move magnet through mixture.
  • Iron particles stick to magnet.
  • Non-magnetic parts remain.
Real-world Application

Our textbook shows separating iron filings from sand. At home, we remove pins fallen in flour using this method. Factories use it to recycle metals.

Question 6:
Explain how sieving is used to separate mixtures in everyday life. Give one NCERT example and a real-world application.
Answer:
Concept Overview

Sieving separates particles of different sizes using a sieve. It is useful for dry mixtures.


Process Explanation
  • A sieve has tiny holes allowing smaller particles to pass through.
  • Larger particles remain on top.

Real-world Application

Our textbook shows sieving flour to remove lumps. At home, we sieve sand to remove pebbles before construction work.

Question 7:
Describe the sedimentation and decantation method with an NCERT example and a daily use case.
Answer:
Concept Overview

Sedimentation lets heavier particles settle, while decantation pours out the clear liquid.


Process Explanation
  • Mixture is left undisturbed for solids to settle.
  • Clear liquid is carefully poured out.

Real-world Application

Our textbook uses this to clean muddy water. At home, we separate rice water after washing rice using this method.

Question 8:
How does filtration help separate mixtures? Provide an NCERT example and a household application.
Answer:
Concept Overview

Filtration uses a filter paper or cloth to separate insoluble solids from liquids.


Process Explanation
  • The mixture is poured through a filter.
  • Solid residue is left behind.

Real-world Application

Our textbook shows filtering tea leaves from tea. At home, we filter juice to remove pulp using a strainer.

Question 9:
Explain evaporation as a separation technique with an NCERT example and a practical use.
Answer:
Concept Overview

Evaporation heats a solution to leave behind solids after liquid turns to vapor.


Process Explanation
  • Solution is heated until liquid evaporates.
  • Solid remains in the container.

Real-world Application

Our textbook shows obtaining salt from seawater. At home, we dry wet clothes in the sun using evaporation.

Question 10:
What is handpicking? Give an NCERT example and a situation where you would use it.
Answer:
Concept Overview

Handpicking involves manually separating larger impurities from a mixture.


Process Explanation
  • Visible unwanted particles are removed by hand.
  • Used when components differ in size/color.

Real-world Application

Our textbook shows removing stones from rice. At home, we handpick spoiled fruits from fresh ones before cooking.

Question 11:
Explain the process of sedimentation and decantation with a real-life example. How is this method useful in our daily lives?
Answer:

The process of sedimentation and decantation is a method used to separate insoluble solids from liquids. Sedimentation involves allowing the mixture to stand undisturbed so that the heavier solid particles settle down at the bottom due to gravity. Decantation is the process of carefully pouring out the clear liquid without disturbing the settled solids.


Real-life example: When muddy water is left in a bucket for some time, the soil particles settle at the bottom, and the clear water can be poured out carefully.


Usefulness in daily life: This method is commonly used in households to clean rice or pulses before cooking. It helps remove dirt and impurities, ensuring cleaner and safer food.


Additional information: Sedimentation is also used in water treatment plants to separate impurities from water before further purification steps.

Question 12:
Describe the winnowing method of separation with a diagram. How is it different from handpicking?
Answer:

Winnowing is a method used to separate lighter and heavier components of a mixture using wind or air.

Process:
1. The mixture (like husk and grains) is dropped from a height.
2. The lighter husk is blown away by the wind, while the heavier grains fall straight down.

Diagram: (Imagine a farmer dropping grain from a basket; husk flies away, grains collect below.)

Difference from handpicking:

  • Winnowing uses wind to separate lighter and heavier particles.
  • Handpicking involves manually removing impurities (like stones from rice), which is time-consuming and not suitable for fine particles.

Application: Farmers use winnowing to separate chaff from grains after threshing. It is a quick and efficient method for large quantities.

Question 13:
Describe the winnowing method of separation with a diagram (explanation if diagram is not possible). How is it different from hand-picking?
Answer:

Winnowing is a traditional method used to separate lighter and heavier components of a mixture by using wind or air. It is commonly used in agriculture to separate husk from grains.


Process:

  • The mixture (e.g., wheat and husk) is dropped from a height.
  • The lighter husk is blown away by the wind, while the heavier grains fall straight down.

Difference from hand-picking:

  • Winnowing relies on wind to separate components, while hand-picking involves manually removing impurities.
  • Winnowing is faster for large quantities, whereas hand-picking is time-consuming but more precise.

Diagram Explanation: (If drawing is not possible) Imagine a farmer standing on a high platform, dropping grain and husk mixture. The wind carries the husk away, while the grains collect in a pile below.


This method is eco-friendly and does not require any machinery, making it ideal for rural areas.

Question 14:
Describe the winnowing method of separation with a suitable example. Why is this method particularly useful for farmers?
Answer:

Winnowing is a traditional method used to separate lighter and heavier components of a mixture by using wind or blowing air. The lighter particles are carried away by the wind, while the heavier particles fall straight down.


Example: Farmers use winnowing to separate husk from grains. After threshing, the mixture of grains and husk is dropped from a height. The wind blows away the lighter husk, leaving the heavier grains behind.


Usefulness for farmers: This method is cost-effective and does not require any machinery, making it ideal for small-scale farmers. It helps in obtaining clean grains for storage or selling.


Additional tip: Winnowing is also used in households to separate impurities like dust or small insects from flour or rice before cooking.

Question 15:
Explain the sedimentation and decantation method of separation with a real-life example. How is this method useful in everyday life?
Answer:

The sedimentation and decantation method is used to separate insoluble solids from liquids. Sedimentation is the process where heavier particles settle down at the bottom of the container when left undisturbed. Decantation involves pouring out the clear liquid without disturbing the settled particles.


Example: A common real-life example is separating mud from water. When muddy water is left undisturbed, the mud particles settle at the bottom due to gravity. The clear water can then be carefully poured out, leaving the mud behind.


Usefulness: This method is widely used in households to clean drinking water, in wastewater treatment plants, and even in cooking (e.g., separating rice from excess water). It is a simple, cost-effective method that does not require any special equipment.

Question 16:
Describe the winnowing process with a diagram (explanation if diagram is not possible). How is this method different from hand-picking?
Answer:

Winnowing is a method used to separate lighter particles from heavier ones using wind or air. It is commonly used in agriculture to separate husk from grains.


Process:

  • Step 1: The mixture of grain and husk is dropped from a height.
  • Step 2: Wind blows away the lighter husk, while the heavier grains fall straight down.
  • Step 3: The grains are collected separately.


Difference from Hand-Picking: Hand-picking involves manually removing impurities from a mixture, which is time-consuming and only works for larger particles. Winnowing, on the other hand, uses natural wind force and is efficient for separating fine, lightweight particles from heavier ones.


Diagram Explanation: Imagine a farmer standing on a raised platform, dropping a mixture of wheat and husk. The wind carries the husk away, while the wheat falls into a pile below.

Question 17:
Explain the process of sedimentation and decantation with a real-life example. How is this method useful in everyday life?
Answer:

The process of sedimentation and decantation is a simple method used to separate insoluble solids from liquids. Sedimentation involves allowing the mixture to stand undisturbed so that the heavier solid particles settle down at the bottom due to gravity. Decantation is then used to carefully pour out the clear liquid without disturbing the settled solids.


Real-life example: When muddy water is left in a bucket for some time, the mud particles settle at the bottom, and the clear water can be poured out carefully.


Usefulness in everyday life: This method is commonly used in households to clean rice or pulses before cooking. It helps remove dirt and impurities, ensuring cleaner and safer food.


Additional tip: Sedimentation is also used in water treatment plants to separate suspended particles from water before further purification.

Case-based Questions (4 Marks) – with Solutions (CBSE Pattern)

These 4-mark case-based questions assess analytical skills through real-life scenarios. Answers must be based on the case study provided.

Question 1:
Riya observed her mother separating tea leaves from prepared tea using a strainer. Explain the method and give another example from NCERT.
Answer:
Case Summary

Riya's mother uses a strainer to separate tea leaves from tea.

Scientific Principle
  • This is filtration, where a sieve retains larger particles.
Solution Approach

Our textbook shows filtering sand from water using a filter paper. Another example is separating pasta from water using a colander.

Question 2:
During a picnic, Aman saw muddy water in a bottle settle clear after some time. Name the method and explain with an NCERT example.
Answer:
Case Summary

Muddy water clears as particles settle at the bottom.

Scientific Principle
  • This is sedimentation followed by decantation.
Solution Approach

We studied how rice and water are separated by decantation. Similarly, sand settles in water, leaving clear liquid above.

Question 3:
Priya’s grandmother separates husk from wheat flour by shaking the sieve. Identify the method and give a real-life application.
Answer:
Case Summary

Husk is separated from flour by shaking a sieve.

Scientific Principle
  • This is sieving, where finer particles pass through holes.
Solution Approach

Our textbook shows sieving flour to remove lumps. In kitchens, we sieve powdered sugar for baking.

Question 4:
At a construction site, workers separate pebbles from sand using a wire mesh. Explain the process and relate it to an NCERT activity.
Answer:
Case Summary

Pebbles are separated from sand using a mesh.

Scientific Principle
  • This is sieving, based on particle size differences.
Solution Approach

We studied separating gravel from sand in NCERT. Similarly, tea strainers separate leaves from liquid.

Question 5:
Riya observed that tea leaves settle at the bottom of her cup. Which method can separate them from the liquid? Explain with another example from NCERT.
Answer:
Case Summary

Tea leaves settle due to gravity, forming a residue.

Scientific Principle
  • Sedimentation and decantation separate insoluble solids from liquids.
Solution Approach

We studied that decantation pours out clean liquid, leaving solids behind. Our textbook shows muddy water clearing when soil settles. Similarly, we can separate rice from washing water this way.

Question 6:
Ami mixed salt and sand. Which two-step process can separate them? Describe using NCERT’s common salt example.
Answer:
Case Summary

Salt dissolves in water, but sand doesn’t.

Scientific Principle
  • Dissolution and filtration separate soluble and insoluble solids.
Solution Approach

We dissolve salt in water, filter sand out, then evaporate water to get salt. Our textbook shows this in seawater salt production. At home, we clean lentils similarly.

Question 7:
At a construction site, workers sieve gravel from sand. Name the method and compare it to NCERT’s flour sieving example.
Answer:
Case Summary

Sieving separates particles of different sizes.

Scientific Principle
  • Sieving uses mesh to retain larger particles.
Solution Approach

We studied that flour sieving removes lumps, similar to gravel separation. Our textbook shows sieving in wheat flour preparation. At home, we sieve tea powder for finer particles.

Question 8:
Oil floats on water in a mixture. Which method separates them? Relate to NCERT’s butter from milk example.
Answer:
Case Summary

Oil and water form distinct layers due to density differences.

Scientific Principle
  • Separating funnel or decantation isolates immiscible liquids.
Solution Approach

We pour oil out carefully, leaving water. Our textbook shows cream separation from milk by centrifugation. Similarly, we remove ghee from curd by skimming.

Question 9:
Riya noticed tea leaves settling at the bottom of her cup. She wants to separate them. Which method would she use? Explain with an example from NCERT.
Answer:
Case Summary

Riya wants to separate tea leaves from her tea.

Scientific Principle

We studied sedimentation and decantation for separating insoluble solids from liquids.

Solution Approach
  • Let the leaves settle (sedimentation).
  • Pour out the tea carefully (decantation).

Our textbook shows how farmers use this to clean rice by removing muddy water.

Question 10:
At a construction site, workers mix sand and cement. Later, they need to separate them. Which technique works best? Compare it to an NCERT example.
Answer:
Case Summary

Workers need to separate sand and cement powder.

Scientific Principle

We learned sieving separates solids of different sizes using a mesh.

Solution Approach
  • Use a fine sieve to retain cement.
  • Sand particles fall through.

Like in NCERT, sieving separates flour from bran in wheat grinding.

Question 11:
During monsoon, rainwater collects dirt and oil on roads. How can municipalities clean it? Relate to NCERT's water purification method.
Answer:
Case Summary

Rainwater mixed with oil and dirt needs cleaning.

Scientific Principle

Our textbook teaches filtration using layers of sand and gravel.

Solution Approach
  • Pass water through sand beds (removes dirt).
  • Use cloth filters for oil (like NCERT's filter paper).

Similar to filtering river water in villages.

Question 12:
A chef accidentally mixes salt and lentils. Suggest a separation method and compare it to how NCERT explains separating husk from grain.
Answer:
Case Summary

Salt and lentils need separation after mixing.

Scientific Principle

We studied handpicking for mixtures where components differ in size/color.

Solution Approach
  • Pick lentils manually (large size).
  • Remaining salt can be sieved.

Like NCERT's example of removing stones from rice by hand.

Question 13:

Rahul observed that his mother uses a sieve to separate wheat flour from impurities before making chapatis. However, when she tried to separate sand from water, the sieve did not work. Help Rahul understand:

  • Why the sieve worked for flour but not for sand-water mixture?
  • Name the correct method to separate sand from water and explain it briefly.
Answer:

Answer:

Sieve works based on the difference in particle size. Wheat flour particles are larger than the sieve holes, while impurities are smaller, allowing separation. However, sand and water particles are both smaller than sieve holes, making it ineffective.


The correct method is sedimentation and decantation:

  • Let the sand settle at the bottom (sedimentation).
  • Carefully pour out the water (decantation).

Alternatively, filtration using a filter paper can also separate sand from water.

Question 14:

Priya noticed that her grandmother separates tea leaves from prepared tea using a strainer. Later, she saw her mother using a similar method to separate paneer from whey while making cheese. Answer the following:

  • What is the common separation method used in both cases?
  • How does this method work? Explain with another daily-life example.
Answer:

Common separation method:
Both cases use filtration, where a porous material (strainer/muslin cloth) allows liquids to pass through while retaining solids.

How it works:

  • The tea leaves are larger than the strainer holes, so they get trapped, while liquid tea passes through.
  • Similarly, paneer (solid) is separated from whey (liquid) using a muslin cloth as the filter.

Another example:
Separating pulses from water after washing them using a sieve. The water drains out, leaving clean pulses behind.

Question 15:

Priya noticed that her grandmother stores rice and pulses together in a container. Sometimes, small stones or husk get mixed in. Suggest a step-by-step method to separate:

  • Rice from pulses
  • Stones/husk from the mixture

Explain the scientific principle behind each step.

Answer:

Answer:

Step 1: Separating rice from pulses
Use handpicking since rice and pulses differ in size, shape, and color, making manual separation easy.


Step 2: Removing stones/husk

  • For stones: Use winnowing—toss the mixture in air; lighter husk blows away, while heavier stones fall separately.
  • For husk: Use sieving—husk is smaller than rice/pulses and passes through the sieve.

These methods rely on differences in weight, size, and density.

Question 16:

Rahul observed that his mother uses a sieve to separate wheat flour from impurities before making chapatis. However, when she tried to separate sand from water, the sieve did not work. Help Rahul understand:

  • Why did the sieve work for wheat flour but not for sand?
  • Which separation method would be suitable for sand and water? Explain.
Answer:

Answer:

A sieve works based on the size difference of particles. Wheat flour particles are smaller than the sieve holes, allowing them to pass through, while larger impurities like husk are retained. However, sand particles are too small to be separated from water using a sieve because they pass through the holes along with water.


The suitable method for separating sand from water is sedimentation and decantation or filtration:

  • Sedimentation and Decantation: Sand settles at the bottom when left undisturbed, and water can be poured out carefully.
  • Filtration: A filter paper can trap sand while allowing water to pass through.

These methods rely on differences in density (sedimentation) or particle size (filtration).

Question 17:

Priya noticed that her grandmother stores rice and pulses together in a container but removes small stones and dust before cooking. Answer the following:

  • Name the separation method her grandmother likely uses to remove stones.
  • How can dust be separated from rice? Explain the process.
Answer:

Answer:

Priya’s grandmother likely uses handpicking to remove small stones because they are larger and easily distinguishable from rice and pulses.


To separate dust from rice, the following methods can be used:

  • Winnowing: Rice and dust are dropped from a height. Lighter dust particles are blown away by wind, while heavier rice grains fall straight down.
  • Sieving: A fine sieve can separate tiny dust particles from rice as the dust passes through the holes.

These methods utilize differences in weight (winnowing) or size (sieving).

Question 18:
Rahul observed that his mother uses a sieve to separate flour from small stones before making dough. Based on this, answer the following:
(a) Name the method of separation used here.
(b) Explain why this method is suitable for this purpose.
(c) Give one more example where this method is used in daily life.
Answer:

(a) The method used here is sieving.

(b) Sieving is suitable because it allows smaller particles like flour to pass through the holes of the sieve, while larger particles like stones are retained. This ensures the flour is clean and safe to use.

(c) Another example is separating tea leaves from prepared tea using a strainer.

Question 19:
During a school picnic, students noticed muddy water in a pond. Their teacher explained how to clean it using a simple method. Answer the following:
(a) Name the method that can be used to separate mud from water.
(b) Describe the process step-by-step.
(c) Why is this method effective for such mixtures?
Answer:

(a) The method used is sedimentation and decantation.

(b) The steps are:
1. Allow the muddy water to stand undisturbed in a container.
2. Heavier mud particles settle down at the bottom due to gravity (sedimentation).
3. Gently pour out the clear water from the top without disturbing the sediment (decantation).

(c) This method is effective because mud particles are insoluble and heavier than water, making them settle down easily.

Question 20:
Rahul observed that his mother uses a sieve to separate flour from small pebbles. Based on this, answer the following:
a) Name the method of separation used here.
b) Explain why this method is suitable for this purpose.
c) Give one more example where this method is used in daily life.
Answer:

a) The method of separation used here is sieving.

b) Sieving is suitable because it allows smaller particles like flour to pass through the holes of the sieve, while larger particles like pebbles are retained. This works due to the difference in particle size.

c) Another example is separating tea leaves from prepared tea using a strainer.

Question 21:
Priya noticed that muddy water becomes clear when left undisturbed for some time. Answer the following:
a) Identify the separation method observed.
b) Why does this happen?
c) Name one substance that can be separated by this method but not by filtration.
Answer:

a) The separation method observed is sedimentation and decantation.

b) This happens because the heavier solid particles (mud) settle down at the bottom due to gravity, while the clearer water remains on top, which can then be poured out carefully.

c) Sand mixed with water can be separated by sedimentation and decantation but not by filtration if the sand particles are too fine and clog the filter.

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