Pause and Ponder
Q1. While eating the pulao, Nani observes that Malli is separating whole black peppers from the pulao and is placing them aside on his plate. Valli playfully teases, "Wow! This is a handpicking method, nice one!" What is handpicking?
Answer:
Handpicking is the method of picking by hand from a mixture, such as removing small stones and husk from wheat and rice. It is done on the basis of differences in size, colour, and shape of the particles. It is convenient when the particles to be removed are present in small quantities and can easily be picked by hand.
Q2. What do you infer from Fig. 9.4? Do both the components, wheat grains and husk, fall at the same place? Which of the two components get blown away? Can the wind separate the two components?
Answer:
From Fig. 9.4, we can infer that winnowing is being done. Wheat grains and husk do not fall at the same place. The lighter component, husk, gets blown away by the wind, while the heavier wheat grains fall down near the farmer. Yes, the wind can separate the two components because husk is lighter than wheat grains.
Q3. Carefully observe a sieve. Are all the holes of the sieve the same size? Will sieving work if the holes of the sieve are larger than the substances? Is there any difference in the size between the particles that pass through the sieve and the particles that remain on the sieve?
Answer:
Yes, generally the holes of a sieve are all the same size. Sieving will not work properly if the holes of the sieve are larger than the substances, because then all particles, including the larger ones, might pass through. The particles that pass through the sieve are smaller in size than the holes, while the particles that remain on the sieve are larger in size than the holes.
Revise, Reflect, Refine
Exercises
Think and Answer
Let us think
Q1. A small amount of puffed rice is mixed with chana dal. Can you think of separating the mixture by any method other than handpicking?
Answer:
Yes, we can separate the mixture of puffed rice and chana dal by winnowing. Since puffed rice is lighter than chana dal, when we blow air or use a fan, the puffed rice will blow away while the chana dal remains behind. We can also use sieving if there is a difference in size between the two.
Q2. Valli is unable to separate husk from rice in a closed room. How can you help her?
Answer:
In a closed room, there is no wind or air flow. To help Valli separate husk from rice, we can use a fan or blow air using our mouth. If that doesn't work, we can take the mixture outside where there is natural wind. Alternatively, we can use a sieve if the husk particles are larger or smaller than rice grains, or handpick the husk if the quantity is small.
Q3. Have you ever observed white patches on the dark coloured clothes you wear during hot summers? How are these patches formed?
Answer:
White patches on dark coloured clothes during hot summers are formed due to the evaporation of sweat. Sweat contains water and dissolved salts. When we sweat, the water evaporates due to heat, leaving behind the salt crystals on the clothes. This is similar to the process of obtaining salt from seawater by evaporation.
Q4. In the chapter 'Materials Around Us', you have studied that oil does not mix with water and forms a separate layer when left undisturbed for some time. Which method of separation would you use to separate oil and water?
Answer:
To separate oil and water, we can use decantation. Since oil is lighter than water and forms a layer on top, we can tilt the vessel carefully and pour out the oil, leaving the water behind. Alternatively, we can use a separating funnel, but for simple mixtures, decantation works well.
Check your progress
Let us enhance our learning
Q1. What purpose does handpicking serve in the process of separation? ?(i) Filtration (ii) Sorting (iii) Evaporation (iv) Decantation
Answer:
(ii) Sorting
Q2. Which of the following substances are commonly separated using the churning method? (i) Oil from water (ii) Sand from water (iii) Cream from milk (iv) Oxygen from air
Answer:
(iii) Cream from milk
Q3. 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
Q4. State with reason(s) whether the following statements are True [T] or False [F]. Also, correct the False statement(s). (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.
Answer:
True
True
False
True
?False
Q5. Match the mixtures in Column I with their method of separation in Column II
Answer:
(i) Gram flour 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
Q6. In what situations would you use decantation instead of filtration to separate solids from liquids?
Answer:
Decantation is used when the solid particles are heavy enough to settle at the bottom of the liquid after standing undisturbed, such as sand or mud in water.
Q7. Can you relate the presence of nasal hair to any separation process?
Answer:
Yes. Nasal hair acts like a filter. It traps dust and other suspended particles from the air before they enter the lungs.
Q8. During the COVID-19 pandemic, all of us wore masks. Generally, what material are they made of? What is the role of these masks?
Answer:
Masks are generally made of layers of non-woven fabric. They filter dust, droplets and microorganisms, helping to prevent the spread of diseases.
Q9. A mixture containing potatoes, salt and sawdust has been given to you. Outline a stepwise procedure for separating each component from this mixture.
Answer:
Step 1: Separate the potato pieces from the mixture by handpicking.
Step 2: Add water to the remaining mixture. The salt dissolves in water, while the sawdust floats on the surface.
Step 3: Remove the floating sawdust by decantation or handpicking.
Step 4: Heat the salt solution to evaporate the water.
Step 5: Collect the salt left behind after evaporation.
Q10. Read the following 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/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:
Suitable title:
Leela's Presence of Mind
Correct options:
Thirsty
Water
Unfit
Filtered
Muslin cloth
Boiled
Cooling
Filtered
Fit