NCERT Solutions Curiosity Chapter 6 Chapter exercises — Let us enhance our learning
Book page 119 to 121 Updated on2026-09-05
Q1.
Visit your kitchen and observe how your parents have organised various edibles. Can you suggest a better sorting method? Write it in your notebook.
Answer
What to do: stand in your kitchen and list what is kept where. Then ask two questions of every shelf — what property was used to group these? and can I find things faster with a different property?
What you will usually find:
Whole spices and powdered masalas in a masala dabba near the stove.
Pulses and grains — rice, wheat flour, dal, rajma — in big airtight jars.
Sugar, salt, tea and oil close to where tea is made.
Vegetables, milk and leftovers in the refrigerator.
Onions, potatoes and garlic in a basket outside, in the dark and air.
Sample answer — a better sorting method:
Sort first by how often it is used. Salt, sugar, tea, oil and the masala dabba go on the shelf you can reach without a stool; festival items go on the top shelf.
Then sort by what the food needs. Things that spoil in warmth (milk, curd, vegetables) → refrigerator; things that spoil in damp (biscuits, papad, flour) → airtight jars; things that spoil in light (oil, ghee) → a closed cupboard.
Use transparent jars of the same size and stick a label with the name and the date of filling. You can see at a glance what is running out.
Keep raw and cooked food apart, and keep soap, phenyl and detergent on a completely different shelf, never above food.
Follow ‘first in, first out’ — push the older packet to the front so it gets used first and nothing is wasted.
Why this is better: the old arrangement usually groups things by habit. The new one groups them by properties — how fast they are used, and what makes them spoil. Grouping by a useful property is exactly what classification means, and it saves time and food.
Q2.
Unscramble the letters (Column I) and match with their properties (Column II). Column I: (i) T R E M A T, (ii) U L S B E L O, (iii) T N E R P A S N A R T, (iv) E R U S T L. Column II: (a) Objects can be seen clearly through it, (b) Occupies space and has mass, (c) Shiny surface, (d) Mixes completely in water.
Answer
Unscramble first, then match each word with its own definition.
Column I (scrambled)
Unscrambled word
Matches
Column II
(i) T R E M A T
MATTER
(b)
Occupies space and has mass
(ii) U L S B E L O
SOLUBLE
(d)
Mixes completely in water
(iii) T N E R P A S N A R T
TRANSPARENT
(a)
Objects can be seen clearly through it
(iv) E R U S T L
LUSTRE
(c)
Shiny surface
Final answer: (i) → (b), (ii) → (d), (iii) → (a), (iv) → (c)
Tip: Count the letters before you start. TNERPASNART has 11 letters and so does TRANSPARENT, with two A’s, two N’s, two R’s and two T’s — the count is a quick way to check that you have unscrambled it correctly.
Q3.
The containers which are used to store materials in shops and at home are usually transparent. Give your reasons for this.
Answer
Because a transparent container lets you see what is inside without opening it. That single property gives several practical advantages.
You can identify the contents at a glance. A shopkeeper with fifty jars finds the rajma in a second, without opening and closing lids.
You can see how much is left, so you know when to refill the sugar jar or reorder stock.
You can check the quality — insects in the flour, fungus on the pickle, a change of colour, stones among the pulses — all are visible from outside.
The food stays safe. Every time a container is opened, air, moisture, dust and flies get in. A transparent jar can be checked without opening it, so the food stays fresh longer.
It attracts customers. Sweets, dry fruits and biscuits in glass jars look inviting and the buyer can judge them before buying.
It saves time and avoids mistakes — no chance of adding salt instead of sugar.
When an opaque container is better instead: for things that are spoiled by light — mustard oil, ghee, medicines, some syrups — shops use dark or opaque containers on purpose. So the material is always chosen to suit the purpose, not by habit.
Q4.
State whether the statements given below are True [T] or False [F]. Correct the False statement(s). (i) Wood is translucent while glass is opaque. (ii) Aluminium foil has lustre while an eraser does not. (iii) Sugar dissolves in water whereas sawdust does not. (iv) An apple is a matter because it occupies no space and has mass.
Answer
Statement
T / F
Corrected statement
(i) Wood is translucent while glass is opaque.
False
Wood is opaque while glass is transparent. Nothing can be seen through wood; things are seen clearly through glass.
(ii) Aluminium foil has lustre while an eraser does not.
True
Aluminium is a metal and shines; an eraser is rubber and is non-lustrous.
(iii) Sugar dissolves in water whereas sawdust does not.
True
Sugar is soluble in water; sawdust is insoluble and floats on the surface.
(iv) An apple is a matter because it occupies no space and has mass.
False
An apple is matter because it occupies space and has mass.
Where each false statement goes wrong: statement (i) simply swaps the two words — it describes glass with wood’s property and wood with glass’s. Statement (iv) gets the mass right but denies that the apple takes up space; if that were true the apple could not be held in your hand at all. Matter must satisfy both conditions — occupy space and have mass.
Q5.
We see chairs made up of various materials, such as wood, iron, plastic, bamboo, cement and stones. Following are some desirable properties of materials which can be used to make chairs. Which materials used to make chairs fulfil these properties the most? (i) Hardness (does not bend or shake on sitting even after long use). (ii) Lightweight (easy to lift or to take from one place to another). (iii) Does not feel very cold when sitting during winters. (iv) Can be cleaned regularly and made to look new even after long use.
Answer
Desirable property
Material that fulfils it most
Why
(i) Hardness — does not bend or shake even after long use
Iron (also stone and cement)
Iron is very hard and strong; an iron chair does not bend or wobble even after years. Stone and cement benches never bend at all.
(ii) Lightweight — easy to lift and carry
Plastic (bamboo and cane are also light)
A plastic chair can be lifted by one child with one hand; an iron or stone chair cannot be moved alone.
(iii) Does not feel very cold in winter
Wood and bamboo (plastic is also fine)
Wood and bamboo are poor conductors of heat — they do not take heat away from the body. Iron, stone and cement pull heat from you quickly and feel icy.
(iv) Can be cleaned regularly and looks new even after long use
Plastic (polished wood and painted iron come next)
Plastic has a smooth surface, does not soak up water, does not rust and does not get eaten by termites, so a wipe with a wet cloth makes it look new.
Why no single material wins everything: iron is the hardest but the heaviest and the coldest; plastic is light and washable but bends under a heavy person over time; wood is warm and strong but can be attacked by termites and needs polishing. A material is chosen for the purpose — that is why school classrooms use light plastic chairs, gardens use iron benches, and village verandas use bamboo mudhas.
Q6.
You need to have containers for collection of: (i) food waste, (ii) broken glass and (iii) wastepaper. Which materials will you choose for containers of these types of waste? What properties of materials do you need to think of?
Answer
Waste to be collected
Material chosen for the container
Properties that made you choose it
(i) Food waste (wet waste)
Thick plastic bin with a tight lid — or a steel bucket
Water-proof (does not leak or soak up gravy), does not rot, does not rust, smooth so it can be washed daily, has a lid to keep out flies and smell. A paper or cardboard box would become soggy and tear.
(ii) Broken glass
A hard, thick-walled container — a metal drum or a rigid, thick plastic bucket with a lid
Hard and strong so sharp edges cannot pierce it, thick walls so nobody gets cut while carrying it, and a lid so pieces do not fly out. A polythene bag or a paper bag would be cut open at once.
(iii) Wastepaper (dry waste)
A cardboard carton, a cane basket or a light plastic bin — no lid needed
Paper is light, dry and harmless, so the container only has to be light, cheap and easy to empty. It must be kept dry and away from fire.
The properties to think about before choosing any container:
Hardness and strength — will the waste tear or pierce it?
Water-proof or absorbent — will wet waste leak through?
Does it rust or rot when it stays wet?
Weight — can it be lifted and emptied easily when full?
Ease of cleaning — a smooth, non-absorbent surface washes clean.
Cost and reuse — it should last many months.
Did you know? Municipalities across India use a colour code for exactly this reason — green bins for wet (food) waste, blue for dry recyclable waste like paper and plastic, and black or red for hazardous waste such as broken glass, blades and used batteries.
Q7.
Air is all around us but does not hinder us from seeing each other. Whereas, if a wooden door comes in between, we cannot see each other. It is because air is ________ and the wooden door is ________. Choose the most appropriate option: (i) transparent, opaque (ii) translucent, transparent (iii) opaque, translucent (iv) transparent, translucent
Answer
Correct option: (i) transparent, opaque.
Air is transparent — light passes straight through, so we see each other clearly
A wooden door is opaque — no light passes through, so we see nothing at all
Why the other options are wrong:
(ii) translucent, transparent — if air were translucent everything would look hazy, and if the door were transparent we could see through it like a window.
(iii) opaque, translucent — this is exactly the reverse of the truth.
(iv) transparent, translucent — air is right, but a wooden door is not translucent; you cannot see even a blurred shape through it. If it were made of frosted glass, this option would be correct.
The clue in the question itself: the words “does not hinder us from seeing” mean see clearly → transparent. The words “we cannot see each other” mean see nothing → opaque. Had the question said “we can see a shadow but not clearly”, the answer would have been translucent.
Q8.
Imagine you have two mysterious materials, X and Y. When you try to press material X, it feels rigid and does not change its shape easily. On the other hand, material Y easily changes its shape when you press it. Now, when you mix both materials in water, only material X dissolves completely, while material Y remains unchanged. What can materials X and Y be? Can you identify whether material X is hard or soft? What about material Y? Justify your answer.
Answer
Read off the two clues given for each material and put them together.
Material X
Material Y
On pressing
Rigid, does not change shape easily
Changes shape easily
So it is
Hard
Soft
In water
Dissolves completely
Remains unchanged
So it is
Soluble
Insoluble
What it can be
Sugar crystals, mishri, common salt (rock salt), alum (phitkari), a glucose tablet
Sponge, eraser (rubber), cotton wool, wax, dough or clay
Justification:
X is hard — the book defines hard materials as those that are difficult to compress or scratch. X stays rigid under your fingers, so it is hard. And since it disappears completely in water, it is soluble. A crystal of sugar or of rock salt fits both clues perfectly.
Y is soft — it can be compressed easily, which is the definition of a soft material. It stays visible in water, so it is insoluble. A sponge or an eraser fits both clues.
The idea being tested: hardness and solubility are two separate, independent properties. A material can be hard and soluble (sugar), hard and insoluble (stone), soft and soluble (jaggery, which crumbles easily), or soft and insoluble (sponge). You must never guess one property from the other.
Q9.
(i) Who am I? Identify me on the basis of the given properties. (a) I have lustre. (b) I can be easily compressed. (c) I am hard and soluble in water. (d) You cannot see clearly through me. (e) I have mass and volume but you cannot see me. (ii) Make your own ‘Who am I?’
Answer
(i) Who am I?
Clue
Property named
Answer
Other correct answers
(a) I have lustre.
Lustrous — a metal
Iron (a freshly cut piece)
Copper, aluminium foil, gold, silver, zinc
(b) I can be easily compressed.
Soft
Sponge
Eraser, cotton wool, pillow, rubber ball
(c) I am hard and soluble in water.
Hard + soluble
Sugar (a crystal of mishri)
Common salt or rock salt, alum (phitkari)
(d) You cannot see clearly through me.
Translucent
Butter paper
Frosted glass, thin plastic sheet, oiled paper
(e) I have mass and volume but you cannot see me.
Matter that is invisible — a gas
Air
Oxygen, carbon dioxide, water vapour
Read clue (d) carefully: it says “cannot see clearly”, not “cannot see at all”. That points to a translucent material such as butter paper. Had it said “you cannot see through me at all”, the answer would have been an opaque material such as wood or cardboard.
(ii) Make your own ‘Who am I?’ — sample riddles you can use:
I am hard, transparent and I break if you drop me. Sand is used to make me. Who am I? — Glass
I am soft and non-lustrous, I soak up water at once, and you write on me. Who am I? — Paper
I am lustrous, hard, and a magnet pulls me. Who am I? — Iron
I am white, hard, soluble in water and I make your food tasty. Who am I? — Salt
I am insoluble in water, I float on it, and I come from cutting wood. Who am I? — Sawdust
Tip for making a good riddle: give two or three properties, not one. “I am hard” could be a stone, iron, glass or sugar; “I am hard, white and soluble in water” can only be salt or sugar.
Q10.
You are provided with the following materials—vinegar, honey, mustard oil, water, glucose and wheat flour. Make any two pairs of materials where one material is soluble in the other. Now, make two pairs of materials where one material remains insoluble in the other material.
Answer
Two pairs where one material is soluble in the other:
Pair
What happens on stirring
Glucose + water
The glucose powder disappears completely and the water stays clear — glucose is soluble in water
Honey + water
The honey mixes completely and the water becomes uniformly pale — honey is soluble in water
also correct:Vinegar + water
Vinegar mixes completely with water and no separate layer forms
Two pairs where one material remains insoluble in the other:
Pair
What happens on stirring
Mustard oil + water
The oil breaks into droplets while you stir, then collects as a separate layer on top — insoluble
Wheat flour + water
The water turns milky and the flour slowly settles at the bottom; it never disappears — insoluble
also correct:Wheat flour + mustard oil
The flour stays as visible particles in the oil
How to test any new pair yourself: put a spoonful of the first material into half a glass of the second, stir well, and leave it undisturbed for five minutes. If nothing at all can be seen — no floating layer, no settled powder, no cloudiness — the first is soluble in the second. Anything you can still see means it is insoluble.
Did you know? This is exactly why a puri fried in oil does not get soggy but a puri dropped in water does. Wheat flour does not dissolve in either, but water soaks into it while hot oil does not.