This shows that everyday objects are made from many different materials such as wood, metal, plastic, paper, glass and cloth — and the same object can even use more than one material.

The objects can be grouped in several valid ways, for example:

• By material: metal (spoon, key, lock, pliers), wood (pencil, wooden stand), plastic (comb-like items), glass (glass bowl), paper (books, notebook)
• By hardness: hard (stone, key, lock) vs soft (nothing very soft here, but a marble/ball is compressible compared to stone)
• By lustre: shiny/lustrous (spoon, keys, lock, pliers) vs dull/non-lustrous (notebook, pencil, diya, stone)

Which property did you use? Any one of shape, colour, material or lustre can be used — students commonly use “material” or “shine” as it is the easiest to observe.

Did your friends group objects the same way? Not necessarily — different students often pick different properties, so their groupings look different even though the objects are the same.

What did you learn? The same set of objects can be classified in more than one way, depending on which property is chosen. This is the basic idea behind classification.

These shapes can be grouped:

• By shape: all cubes together, all cones together, all triangular prisms together
• By colour: all pink shapes together, all blue shapes together, all purple shapes together, all orange/yellow shapes together

This confirms that objects can be grouped either by their shape or by their colour — both are valid common properties.

A tumbler can be made using: Plastic, Steel (metal), Glass, and Clay (ceramic) — all of these materials are capable of holding water without letting it pass through.

Ball with the highest bounce: The rubber hand-exercise ball, because rubber is highly elastic and returns most of the energy of the fall.

No. While most lustrous (shiny) materials are metals, some non-metal materials can also be made to shine by polishing them or coating them with a thin layer of plastic, wax, or paint. As the saying goes, “All that glitters is not gold” — shine alone does not confirm that a material is a metal.

Materials that can be compressed or scratched easily are soft; those that resist compressing or scratching are hard. These properties are relative — for example, rubber is harder than sponge but softer than iron.

They chose places made of opaque or translucent materials so that they could not be seen clearly. A wall and a tree trunk are opaque (nothing can be seen through them), while a frosted glass door is translucent (only a hazy outline is visible), so all three places offered good cover to hide behind.

No. Wood is an opaque material — light cannot pass through it, so nothing on the other side can be seen. If the window were made of wood instead of glass, Sheeta’s brother would not have been able to see them at all.

Yes, clean water is transparent — objects can be seen clearly through it. However, it can be made translucent or opaque by mixing something into it, such as mud, ink, milk, or colour — this blocks or scatters light so objects can no longer be seen clearly (or at all) through it.

Prediction/typical result: Pebbles (C) are usually the heaviest, sand (B) comes next, and water (A) is generally the lightest for the same half-filled volume — because different materials packed into the same space have different masses.

This activity shows that even though all three cups occupy the same amount of space (are filled to the same level), they do not have the same mass. The heavier one has more mass; the lighter one has less mass.

Both tumblers have the same capacity, but the two water bottles did not contain the same amount (volume) of water. Since the water in the first tumbler occupies less space than the water in the second, its volume is less — this is why the water levels differ even though the tumblers themselves are identical.

Because the volume of water in the jug was greater than the volume (capacity) the empty bottle could hold. Once the bottle was full, there was no more space left inside it, so the remaining water could not be poured in and spilled over instead.

Yes. Every material occupies some space and has some mass — these two properties, mass and volume, are common to all materials. Anything possessing both of these properties is called matter.

Yes, air is matter — although we cannot see it, it occupies space (it fills a balloon or a room) and it has mass. Similarly, every material around us — water, sand, pebbles, a cup, wood, or any object — occupies space and has mass, so all materials are examples of matter.

As a boon: Plastic is light, strong, cheap, waterproof and easy to mould — it made packaging, medical equipment, electrical insulation, and countless everyday items more affordable and convenient.

As a bane: Most plastic is non-biodegradable — it stays in the environment for hundreds of years, pollutes land and water, and harms wildlife that ingest or get trapped in it.

Overall, plastic is a boon when used responsibly (reused, recycled, reduced) and a bane when used carelessly and discarded — so the answer depends on how wisely we use and dispose of it.

In most kitchens, edibles are organised by type — spices in small jars together, pulses and grains in larger containers, and liquids like oil separately. A better sorting method could be to group items by:

• Frequency of use — daily-use items (salt, sugar, tea) kept within easy reach, occasional items stored higher up or further back
• Container material — using transparent jars for grains/pulses so contents are visible at a glance, and airtight opaque containers for items that spoil in light (like spices)
• Perishability — separating perishable items (needing refrigeration) from non-perishable dry goods

Transparent containers let the contents be seen clearly from outside without opening them. This makes it easy to:

• Identify what is stored inside quickly
• Check how much of the item is left (quantity remaining)
• Check the quality or freshness of the item (colour, spoilage, presence of insects, etc.)
• Attractively display the product to customers in shops

The main properties to consider are: hardness/strength (to resist sharp objects), water-resistance (for wet or moist waste), and ease of cleaning.

Air lets us see clearly through it, so it is transparent. A wooden door does not let any light pass through, so nothing can be seen through it — making wood opaque.

Material X: Hard and soluble in water — for example, common salt or sugar. It resists being compressed (hard) but dissolves completely when mixed in water (soluble).

Material Y: Soft and insoluble in water — for example, a sponge or rubber ball. It changes shape easily when pressed (soft), but does not dissolve or disappear when placed in water (insoluble).

Justification: Hardness/softness depends on how easily a material can be compressed or scratched, while solubility depends on whether a material mixes completely with water — these are two independent properties, and X and Y show opposite behaviour on both counts.

(ii) Make your own “Who am I?”: Example — “I am transparent, I am liquid at room temperature, and many materials dissolve in me. Who am I?” (Answer: Water)

(Vinegar is also soluble in water and could replace glucose or honey in the soluble pair.)

Reasoning: Iron and copper are shiny metals, so they link to “Lustrous.” Glass lets us see through it, so it links to “Transparent.” Wood does not, so it links to “Opaque.” A bottle can be made of plastic or glass. And since iron, copper, wood, glass and plastic all keep a fixed shape at room temperature, they can all be linked to “Solid.”

• Each student randomly picks 9 words from: lustrous, non-lustrous, soluble, insoluble, hard, soft, matter, mass, transparent, opaque, volume, translucent — and writes them in a 3×3 grid.
• The facilitator calls out a word or reads its definition, one at a time, in random order.
• Students tick the word in their grid if they have it.
• The first student to tick off all 9 correctly-marked words shouts “Hurray!” and wins.

This is a classroom activity without a fixed “answer” — it works as a fun way to revise the chapter’s keywords and their meanings.