──────────────────────────────────────────────────────── IN-TEXT QUESTIONS ────────────────────────────────────────────────────────
Question:
“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 use winnowing if there is a gentle breeze or we can blow air. Puffed rice is lighter and will blow away, leaving chana dal behind.
Question:
“Valli is unable to separate husk from rice in a closed room. How can you help her?”
Answer:
• She can switch on a fan or create airflow so that winnowing can be done indoors. Alternatively, she could manually blow air using a bamboo tray.
Question:
“Observe the figure. Does it answer the question? Can you name the process involved?”
(Refers to heating a salt solution in a container)
Answer:
• Yes, it shows that when salt water is heated, the water evaporates, leaving the salt behind.
• The process is called evaporation.
Question:
“Is there any method through which I can get back both salt and water?”
Answer:
• Yes, we can use a process called distillation. In distillation, we heat the salt solution and cool the water vapours separately to get both water and salt back. (Distillation is usually done in special equipment.)
Question:
“In the chapter ‘Materials Around Us’, you have studied that oil does not mix with water. Which method of separation would you use to separate oil and water?”
Answer:
• We can use decantation. Let the oil and water settle in layers. Then gently tilt and pour out the top oily layer from the water.
Question:
“How many layers of cloth do I need to use to get clear water?”
Answer:
• The more layers of cloth you use, the finer the filtering becomes. Usually, 2 or 3 layers can help get cleaner water – but a very thick cloth or multiple layers filter better.
Question:
“Can you name one kitchen appliance which runs on electricity that is used to prepare buttermilk?”
Answer:
• An electric blender (mixer-grinder) can be used to churn curd and get buttermilk.
Question:
“Which method of separation did the carpenter use?”
(Refers to picking nails from sawdust)
Answer:
• He used magnetic separation. A magnet attracts the iron nails and separates them from sawdust.
──────────────────────────────────────────────────────── ACTIVITY QUESTIONS ────────────────────────────────────────────────────────
Activity 9.1 (Let us explore)
Question:
“Which of these components—removed peanut skins or peanuts—are blown away when we rub roasted peanuts and blow on them?”
Answer:
• The lighter peanut skins are blown away, while the heavier peanuts remain.
Activity 9.2 (Let us observe and create)
Question:
“After placing drops of salt solution on thick black paper and letting it dry, what do you observe? Where does the water disappear?”
Answer:
• We see white patches of salt left on the paper.
• The water evaporates into the air.
Activity 9.3 (Let us investigate)
Question:
“What do you observe when you heat the salt solution in a china dish? What remains in the dish after heating?”
Answer:
• The water boils away (evaporates), and salt is left behind in the dish.
Activity 9.4 (Let us experiment)
Question:
“What do you observe if you filter muddy water through a filter paper? Do the mud particles pass through?”
Answer:
• The mud particles stay on the filter paper (residue), and the clear water (filtrate) collects below.
• Mud does not pass through the paper.
Activity 9.5 (Let us design and create)
Question:
“Valli collects pond water which has unwanted substances. Design and create a model of a water filter using simple materials. What do you notice?”
Answer (sample):
• By using layers of gravel, sand, and charcoal, we can filter out larger and smaller particles.
• The filtered water is cleaner than before, but it may still need boiling to make it safe for drinking.
Activity 9.6 (Let us play)
Instruction:
• This is a game about separating substances. There is no direct question, but you identify which separation methods are used and why (for example, handpicking, winnowing, etc.).
──────────────────────────────────────────────────────── EXERCISE QUESTIONS (“Let us enhance our learning”) ────────────────────────────────────────────────────────
Question:
“What purpose does handpicking serve in the process of separation?
(i) Filtration, (ii) Sorting, (iii) Evaporation, (iv) Decantation”
Answer:
• Handpicking helps in sorting (option ii). It separates small amounts of unwanted particles by picking them out.
Question:
“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:
• Cream from milk (option iii) is separated by churning.
Question:
“Which factor is usually essential for the filtration?
(i) Apparatus size, (ii) Presence of air, (iii) Pore size, (iv) Temperature of the mixture”
Answer:
• Pore size (option iii) is most important for filtration.
Question:
“State with reason(s) whether the following statements are True or False. 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:
(i) True. Water evaporates under the Sun, leaving salt behind.
(ii) True. Handpicking is easier when the unwanted component is small in amount.
(iii) False. Puffed rice and rice grains are best separated by winnowing (because puffed rice is lighter).
Correct statement: “A mixture of puffed rice and rice grains can be separated by winnowing.”
(iv) True. Oil floats over lemon water, and you can gently pour off the top oil layer by decantation.
(v) False. Sieving does not work with rice flour mixed into water because the flour is too fine.
Correct statement: “Rice flour and water cannot be separated by simple sieving. We can use filtration with very fine pores or wait for settling.”
Question:
“Match the mixtures in Column I with their method of separation in Column II.
Column I:
(i) Gram flour mixed with black gram
(ii) Chalk powder mixed with water
(iii) Corn mixed with potatoes
(iv) Iron powder mixed with sawdust
(v) Oil mixed with water
Column II:
(a) Handpicking
(b) Magnetic separation
(c) Decantation
(d) Sieving
(e) Filtration”
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
Question:
“In what situations would you use decantation instead of filtration to separate solids from liquids?”
Answer:
• We use decantation when the heavier particles settle at the bottom, and the liquid can be gently poured out. For example, when washing rice or pulses, we can tilt the vessel and pour out the water along with lighter dirt on top.
Question:
“Can you relate the presence of nasal hair to any separation process?”
Answer:
• Yes. Nasal hair acts like a filter. It traps dust and dirt from the air we breathe, just like how filtration removes dirt from water.
Question:
“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 often made of layers of fine cloth or special filter material.
• Their role is to filter out germs and tiny particles so they do not enter our mouth or nose.
Question:
“A mixture containing potatoes, salt, and sawdust has been given to you. Outline a stepwise procedure for separating each component.”
Answer (sample steps):
• First, handpick the bigger pieces (potatoes) from the mixture.
• Next, mix the remaining salt+sawdust with water. Salt dissolves in water, sawdust floats.
• Then scoop out the sawdust from the top or use filtration.
• Finally, boil or evaporate the water to get salt back.
Question:
“Read the following story titled ‘Intelligent Leela’ and tick the most appropriate options. Provide a suitable title for the paragraph.”
Answer (sample):
• Leela saw the water was muddy and not good for drinking.
• She let the mud settle (sedimentation), filtered the water (filtration), then boiled it to kill germs, and cooled it.
• At the end, she served clean water to her father.
• A possible title: “Leela’s Smart Way to Clean Water.”