Choosing the Right Material Notes & Questions | Class 3 Chemistry | Drishti OS

Choosing the Right Material

What you'll learn

Different jobs need different materials, chosen for their special properties.
Waterproof materials (plastic, nylon) are used for umbrellas and raincoats.
Warm materials like wool are used for winter clothes.
Transparent glass is used for windows; flexible, grippy rubber is used for shoe soles; heat-conducting metal is used for cooking pots.

Key concepts

Level 1 — Core idea

Verbal: We choose rubber for shoe soles because it grips the ground and does not let us slip — plastic would be too smooth and slippery.

Symbolic: Right material = matching property (waterproof/warm/transparent/heat-conducting) to the job needed.

Visual: A glass window lets you see through it; a wooden door does not — that is why windows are glass and doors are often wood.

Level 2 — Going deeper

Choosing materials wisely means thinking about what job the object must do, then picking a material with the properties needed for that job.

NCERT anchor

NCERT Looking Around 3 — everyday objects and why they are made of specific materials.

Worked example

Why are umbrellas not made of cotton cloth alone?

Step 1 — Cotton soaks up water easily.
Step 2 — An umbrella must keep water off, not soak it in.
Answer: **Umbrellas use waterproof materials like plastic/nylon, not plain cotton.**

Why are cooking pots usually made of metal, not wood?

Step 1 — Metal conducts (carries) heat well.
Step 2 — Wood does not conduct heat well and can burn.
Answer: **Metal is chosen because it conducts heat well for cooking.**

Common mistakes

Mistake	Why	Fix
Any material works for any job	Not linking property to purpose	Materials are chosen for specific properties suited to the job
Wool is for summer	Mixing up warm and cool clothing	Wool is chosen for winter because it keeps us warm
Glass is opaque	Confusing glass with wood or metal	Glass is chosen for windows because it is transparent
Rubber is slippery on shoe soles	Reversing the real property	Rubber grips the ground, so it is used for shoe soles

Quick check

Why are umbrellas waterproof?
Why do we wear wool in winter?
Why are windows made of glass?
Stretch: Why are shoe soles made of rubber instead of glass?

Revision tip: Ask: "What job must this object do, and which material property helps with that job?"

Open the Practice tab for graded questions on Choosing the Right Material.

Choosing the Right Material