NCERT Solutions Curiosity Chapter 4 Sections 4.1.2 Ductility and 4.1.3 Sonority — In-text Questions

Book page 44 & 45 Updated on2026-09-05

Q1.
Where do you find the use of metal wires?
Answer
Where you see metal wireWhich metal, and why it is used
Electrical fittings in the houseCopper or aluminium — good conductors of electricity
Ornaments — bangles, necklaces, earringsGold, silver — very ductile, so they can be drawn fine and twisted
Stringed instruments — veena, sitar, violin, guitarSteel, brass — a taut metal wire vibrates and gives a clear note
A tea strainer, a sieve, wire meshSteel wire woven into a net
Ropes of suspension bridges and cranesSteel wire, which can bear very heavy loads

The property that makes all this possible is ductility — the property of materials by which they can be drawn into wires.

Did you know? Gold is so ductile that one gram of it can be drawn into a 2 kilometre-long wire.
Q2.
Have you ever seen wires made of coal or sulfur?
Answer

Obviously not. No one has ever seen a wire of coal or of sulfur, and no one ever will.

Pull a copper rod → it stretches thinner and thinner → ductile
Pull a stick of coal or sulfur → it snaps at once → not ductile
Why it happens: to become a wire, a material must be able to stretch without breaking. In a metal the particles slide past one another and stay joined. In coal and sulfur they cannot slide, so the piece cracks the moment it is pulled. Coal and sulfur are non-metals, and non-metals are neither malleable nor ductile.
Q3.
Have you ever noticed the sound produced when a metal spoon, or a metal plate, or a metal coin is dropped on the floor? How is it different from the sound produced when a piece of coal or wood is dropped on the floor?
Answer

The difference is easy to hear.

Object droppedSound producedHow long it lasts
Metal spoon, metal plate, coinA clear ringing soundRings on for a moment after the fall
Piece of coal, block of woodA dull thudStops the instant it lands

This property of metals that enables them to produce a ringing sound is called sonority, and metals are said to be sonorous in nature.

Why it happens: when a metal is struck it keeps vibrating for a while, and those vibrations reach your ear as a long, clear note. Coal and wood stop vibrating almost immediately, so you hear only a short, dull thud.
Did you know? The ring of the school bell and the jingle of ghungroos are both the sonority of metals at work.
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