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Methods for separation notes

All materials are n ot pure on the earth. Many of them are found in combination with other impurities.  Someexamples of mixtures of impure substances — these are materials that contain more than one substance, often with unwanted or foreign particles mixed in:

1. Seawater: a mixture of: Water, salt, and impurities like sand, small organisms, and minerals. It has Impurity:ies like Sand, dirt, and microorganisms.

2.Unclean Rice or Wheat is a Mixture of Grains, small stones, husk, dust with many impurities like stones, dust, husk.

3. Tea with Tea Leaves has a mixture of water, sugar, milk, tea leaves where some impurities like tea leaves (need to be removed before drinking)

4. Tap Water (in some areas) has mixture of: Water, dissolved salts, chlorine, and sometimes rust or dirt from old pipes with many impurities such as rust, dirt, excess minerals.

5. Crude Oil is another impure mixture containing hydrocarbons, sulfur, water, and other compounds where sulfur and other unwanted chemicals are found 

6. Harvested Grains has a mixture of grains, soil, small insects, leaves along with impurities such as soil, insects, plant debris.

Why do we need to separate impurities?

We need to separate substances in daily life for many practical reasons. They are as follows 

1.To Use Useful Components because,  many natural materials are mixtures. We separate them to get the part we need. Example: Milk is separated to get cream and butter and the tea leaves are separated from tea using a strainer.

2.To Remove Harmful or Unwanted Substances as , sometimes, mixtures contain harmful or useless parts that must be removed. Example: Stones are separated from rice or wheat before cooking and water is filtered to remove dirt and germs.

3.To Purify Substances. Separation is needed when we want a pure substance. Example: Salt is separated from seawater through evaporation. Drinking water is purified from impurities.

4.To Sort Materials for Recycling or Reuse. We separate materials so they can be reused or recycled. Example: Plastic, metal, and paper are separated in waste management.

5. To Improve Efficiency in Industry. Industries need pure raw materials, so separation is a key step. Example: Iron is separated from its ore before it is used to make steel.

Methods for separation

Handpicking 

This is a simple method of manually separating substances. It is useful when the components are large enough to be seen individually and are present in small quantities. Everyday example: Removing small stones, dirt, and husk from rice or pulses before cooking.

Threshing

Threshing is the process of beating harvested stalks to separate the grains. For small quantities, this can be done manually by beating the stalks on a hard surface. Large-scale threshing often uses machines. Everyday example: Farmers separating grains of wheat or paddy from their stalks.

Winnowing

Rice winnowing at Pambeguwa of Kubau local government area of Kaduna State
This method uses wind or blowing air to separate heavier and lighter components of a mixture. When a mixture is dropped from a height, the lighter particles are carried away by the wind, leaving the heavier particles to fall straight down. Everyday example: Farmers separating lighter husk from heavier grain.

Sieving

Laboratory sieves BMK
Sieving separates mixtures based on particle size using a mesh or sieve. Smaller particles pass through, while larger ones are retained. Everyday examples: Sifting flour or separating pebbles from sand.

Magnetic separation

This technique uses a magnet to separate magnetic substances from non-magnetic ones, effective for mixtures containing materials like iron. Everyday example: Using a magnet to separate iron pins from sand or flour.

Methods for separating solids and liquids

Sedimentation

Decantazione
Sedimentation is when heavier, insoluble particles in a liquid settle at the bottom due to gravity. Everyday example: Soil particles settling in muddy water.

Decantation

Decantation follows sedimentation and involves carefully pouring off the clear liquid without disturbing the settled solids. Everyday example: Pouring clear water after mud has settled.

Filtration

This method uses a porous filter to separate insoluble solid particles from a liquid. Everyday example: Straining tea to remove leaves.

Evaporation

Evaporation separates a soluble solid dissolved in a liquid by heating the mixture until the liquid turns into vapor, leaving the solid behind.Everyday example: Obtaining salt from seawater.

Method for separating liquids

Fractional distillation lab apparatus unlabeled

There are different methods for separating liquids, depending on whether the liquids are immiscible (do not mix, like oil and water) or miscible (completely mix, like alcohol and water). One common method for separating immiscible liquids is decantation. In this method, the mixture is allowed to stand still until the two liquids form separate layers. The top layer is then carefully poured off, leaving the other behind. For more precise separation, especially in laboratory settings, a separating funnel is used. The mixture is poured into the funnel and allowed to settle. The denser liquid (usually water) settles at the bottom and is released first by opening the tap, while the lighter liquid (like oil) remains above and is collected later. When separating miscible liquids, which mix uniformly, methods like simple distillation are used if the two liquids have significantly different boiling points. In this method, the mixture is heated, and the liquid with the lower boiling point evaporates first. The vapor is then cooled and condensed back into a liquid in a separate container. If the liquids have similar boiling points, fractional distillation is used. This method involves a fractionating column placed above the boiling flask, which allows the vapors to separate more effectively as they rise and condense at different heights based on their boiling points. This method is commonly used in industries to separate components of crude oil or to purify alcohol.

TEXT BOOK QUESTION ANSWERS

Question 1.What purpose does handpicking serve in the process of separation?
(i) Filtration
(ii) Sorting
(iii) Evaporation
(iv) Decantation
Answer:(ii) Sorting

Question 2.Which of the following substances are commonly separated using the churning method?
(i) Oil from water
(iii) Cream from milk
(ii) Sand from water
(iv) Oxygen from air
Answer:(iii) Cream from milk

Question 3.Which factor is usually essential for the filtration?
(i) Apparatus size
(ii) Presence of air
(iii) Pore size
(iv) Temperature of the mixture
Answer:(iii) Pore size

Question 4.State with reason(s) whether the following statements are True [T] or False [F]. Also, correct the False statements).
(i) Salt can be separated from ‘ salt solution by keeping it under the Sun.
(ii) Handpicking should be used only when the quantity of one component is less.
(iii) A mixture of puffed rice and rice grains can be separated by threshing.
(iv) A mixture of mustard oil and lemon water can be separated by decantation.
(v) Sieving is used to separate a mixture of rice flour and water.

Answers:

(i) True. Reason : The water will evaporate leaving the salt behind

(ii) True. Reason: It is easier to handpick small quantities.

(iii) False Reason: Process of threshing is used to separate the grains from the stalks. Correct statement: This mixture can be separated by handpicking or winnowing.

(iv) TrueReason: The oil and water will form separate layers which can be decanted.

(v) FalseReason: Sieving is done to separate solid-solid mixture of different particles size.Correct Statement: Filtration is used to separate a mixture of rice flour and water.

Question 5.Match the mixtures in Column I with their method of separation in Column II.

Answers:
Column I Column II
(i) Grams floour mixed with black gram (d) Sieving
(ii) Chalk powder mixed with water (e) Filtration
(iii) Corn mixed with potatoes (a) Handpicking
(iv) Iron powder mixed with sawdust (b) Magnetic separation
(v) Oil mixed with water (c) Decantation

Question 6.In what situations would you use decantation instead of filtration to separate solids from liquids?
Answer: Decantation method is used when the insoluble solid particles are heavier and settle down at the bottom of the vessel. The liquid is separated from insoluble solids by pouring off the liquid while leaving the solid particles behind as a residue.
While filtration method is used when insoluble particles do not settle down and spreads throughout the solution.

Question 7.Can you relate the presence of nasal hair to any separation process?
Answer: Nasal hair acts like a natural filter, trapping dust, pollen, and other particles from the air we breathe, similar to how a filtration process works to remove solid impurities from a liquid.

Question 8.During the COVID-19 pandemic, all of us wore masks. Generally, what materials are they made of? What is the role of these masks?
Answer:Masks are generally made of multiple layers of fabric or materials such as cotton, polypropylene, or polyester. Their role is to filter out harmful particles, including viruses, from the air we breathe, similar to how filtration processes work to remove impurities from liquids.

Question 9.A mixture containing potatoes, sctlt and sawdust has been given to you. Outline a stepwise procedure for separating each component from this mixture.
Answer:
Step-1 : Handpick the potatoes
Step-2 : Add water to the remaining mixture to dissolve the salt
Step-3 : Filter the mixture to separate the sawdust from the salt solution.
Step-4 : Evaporate the water from the salt solution to obtain the salt.

Question 10.Read the folloiving story titled ‘Intelligent Leela’ and tick the most appropriate options. Provide a suitable title of your choice for the paragraph. Leela was working in the farm with her father when she realised that they left their drinking water at home. Before her father felt thirsty/ hungry, she went to the nearby pond to fetch some water/grains. After obtaining some water in the container, she noticed that the water was muddy and fit/unfit for drinking. To purify the water, she kept it for some time and then she filtered/ churned the muddy water using a piece of paper/muslin cloth. Leela, then, cooled/boiled the water for about 10 minutes in a covered pan. After cooling/ v boiling, she filtered/churned it again and made it fit/unfit for drinking. She served this water to her father while having food, who blessed her and appreciated her efforts.

Answer:Purification of Water:
Leela was working in the farm with her father when she realised that they left their drinking water at home. Before her father felt thirsty/hungry, she went to the nearby pond to fetch some water/grains. After obtaining some water in the container, she noticed that the water was muddy and fit/unfit for drinking. To purify the water, she kept it for some time and then she filtered/churned the muddy water using a piece of paper/muslin cloth. Leela, then, cooled/boiled the water for about 10 minutes in a covered pan. After cooling/boiling, she filtered/churned it again and made it fit/unfit for drinking. She served this water to her father while having food, who blessed her and appreciated her efforts.

Multiple choice questions

1. The process by which tea leaves are separated from tea is

  1. Sedimentation
  2. Decantation
  3. Filtration
  4. Churning

Answer- C-Filtration

2. Churning helps to separate

  1. Butter from buttermilk
  2. Ghee from butter
  3. Pebbles from sand
  4. Blood cells from blood

Answer-A- Butter from buttermilk

 3. Which of the following processes can be used to separate a liquid from an insoluble solid?

  1. Evaporation
  2. Sedimentation
  3. Distillation
  4. Filtration

Answer –D-Filtration

4. Choose the correct statement from the following.

  1. Sedimentation separates curd from milk
  2. Sedimentation requires boiling of mixture
  3. Sedimentation and decantation are same
  4. Sedimentation requires some time to settle the impurities.

Answer –D- Sedimentation requires some time to settle the impurities.

5. The method used in water filtration plants is

  1. Magnetic separation
  2. Winnowing
  3. Handpicking
  4. Threshing

Answer –(A)Magnetic Separation

 6. Threshing is a method where?

  1. Farmers beat stalks to separate grains from stalks
  2. Farmers use severs.
  3. Wind is used to separate husk from grains
  4. All are correct

 Answer – (A) Farmers beat stalks to separate grains from stalks

 7. Salt is separated from ocean water by

  1. Sedimentation
  2. Decantation
  3. Evaporation
  4. Distillation

Answer – (C) Evaporation

8. Which method is used to dry the clothes after washing them?

  1. Sedimentation
  2. Decantation
  3. Evaporation
  4. Distillation

Answer – (C) Evaporation

9. Which method can be used to separate iron and copper?

  1. Crystallisation
  2. Sublimation
  3. Evaporation
  4. Magnetic separation

Answer – (D) Magnetic separation

10. The process of separating cotton from cotton seeds is

  1. Ginning
  2. Winnowing
  3. Handpicking
  4. Condensation

Answer – (A) Ginning