Physical Properties of Metals and Non-metals

Metals are lustrous, hard, malleable, ductile conductors that ring when struck; most non-metals are the opposite. Neither half of that sentence is exceptionless — and the exceptions are exactly what this lesson asks you to remember by name.

In this lesson you will

Identify metallic lustre, hardness, malleability, ductility, conductivity and sonority from a sample or a described test.
Name the everyday use each property explains (wiring, foil, vessels, bells).
State the four groups of physical-property exceptions: mercury and low-melting metals, lustrous iodine, carbon’s allotropes, and the soft alkali metals.
Recall that burning magnesium gives a basic oxide and burning sulphur gives an acidic oxide — the first hint that metals and non-metals differ chemically too.

Metals: lustre, hardness, malleability, ductility

A freshly cleaned metal surface shines — that shine is called metallic lustre, and it is the easiest first test for a metal. Most metals are also hard (though hardness varies a lot from metal to metal), can be hammered into sheets without shattering (malleable), and can be drawn into thin wire (ductile). It is exactly because of malleability and ductility that metals can be shaped into foil, wire and vessels to suit whatever we need.

Conduction and sonority

Metals conduct both heat and electricity well — silver and copper are the best thermal conductors, lead and mercury comparatively poor ones. Metals also produce a ringing sound when struck, a property called sonority — which is why school bells, temple bells and cymbals are made of metal, never of wood, plastic or stone.

Non-metals: the (near) opposite

There are far fewer non-metals than metals. Common examples are carbon, sulphur, iodine, oxygen and hydrogen — all solids or gases except bromine, a liquid. Repeating the same tests on carbon, sulphur and iodine shows non-metals are generally dull, brittle (not malleable or ductile at all), and do not conduct electricity or heat.

The exceptions that matter

Grouping elements by physical properties alone breaks down in four specific, exam-worthy ways:

Mercury is the one metal that is liquid at room temperature; gallium and caesium have such low melting points that they melt sitting in your palm.
Iodine is a non-metal, yet it is distinctly lustrous.
Carbon exists as different allotropes. Diamond is the hardest natural substance known, with a very high melting and boiling point. Graphite — the very same element, arranged differently — conducts electricity, something almost no other non-metal does.
Alkali metals (lithium, sodium, potassium) are so soft they can be sliced with a knife, and have unusually low density and melting points for metals.

Elements are classified far more reliably by chemical properties — covered next.

A first chemical clue: burning in air

Burning magnesium ribbon leaves an ash that turns red litmus blue — a basic oxide. Burning sulphur gives off fumes that, dissolved in water, turn blue litmus red — an acidic oxide. As a general pattern, metals form basic oxides and non-metals form acidic oxides — the opening idea of the next lesson’s chemical properties.

Key terms

Lustre: The shiny appearance of a freshly cut or cleaned metal surface, caused by free electrons reflecting light.
Malleability: The ability of a substance to be hammered or rolled into thin sheets without breaking.
Ductility: The ability of a substance to be drawn into thin wire.
Sonority: The property of producing a ringing sound when struck — why bells and cymbals are cast in metal.
Allotropes: Different physical forms of the same element, with different structures and properties — diamond and graphite are both pure carbon.

Key relationships

Metals (except mercury) are solid at room temperature — but gallium and caesium melt in your palm.
Iodine is a non-metal, yet it is lustrous.
Diamond (an allotrope of carbon) is the hardest known natural substance; graphite (another allotrope of the same element) conducts electricity.
Alkali metals (lithium, sodium, potassium) are so soft they can be cut with a knife, and have low density and low melting points.
Burning magnesium in air gives a basic oxide (turns red litmus blue); burning sulphur gives an acidic oxide (turns blue litmus red).

Activities

Activity 3.1 — Cleaning a metal to reveal lustre

What you do: Take samples of iron, copper, aluminium and magnesium. Note their dull, tarnished appearance, then clean each surface with sandpaper.

What you see: Underneath the dullness, every sample reveals a shining metallic surface.

What it shows: Metals are lustrous in their pure state — the dullness you usually see is a thin surface layer, not the metal itself.

Activity 3.2 — Hardness — and the soft exception

What you do: Try to cut iron, copper, aluminium and magnesium with a knife. Separately, a piece of sodium metal (handled with tongs) is cut on a watch-glass.

What you see: The four common metals resist the knife; sodium cuts as easily as wax or soap.

What it shows: Metals are generally hard, but hardness varies enormously — alkali metals like sodium are a genuine exception, not a measurement error.

Activity 3.3 — Malleability — hammering a metal

What you do: Place iron, zinc, lead and copper in turn on an iron block and strike each with a hammer.

What you see: Each sample flattens and spreads instead of shattering.

What it shows: Metals can be beaten into thin sheets; gold and silver are the most malleable of all.

Activity 3.4 — Ductility — metals as wires

What you do: List every metal wire you can think of from daily life.

What you see: Copper and aluminium wiring, iron and steel wire, gold and silver wire in jewellery.

What it shows: Metals can be drawn into thin wires; gold is the most ductile — one gram can be drawn into a wire about 2 km long.

Activity 3.5 — Metals conduct heat

What you do: Clamp a copper or aluminium wire with a pin fixed to its far end using wax. Heat the near end with a burner.

What you see: The wax melts and the pin drops off, even though the flame never touched that end.

What it shows: Metals are good conductors of heat — silver and copper are the best; lead and mercury are comparatively poor conductors.

Activity 3.6 — Metals conduct electricity

What you do: Build a simple circuit (battery, bulb, switch) with two clip leads left open. Insert a metal sample between the clips.

What you see: The bulb lights up whenever a metal bridges the gap.

What it shows: Metals conduct electricity — which is exactly why household wires are coated in insulating PVC, not left bare.

Activity 3.7 — Do non-metals share these properties?

What you do: Repeat Activities 3.1–3.4 and 3.6 on samples of carbon (coal or graphite), sulphur and iodine, and record everything in one comparison table.

What you see: Non-metals are dull (iodine is a lustrous exception), brittle rather than malleable or ductile, and do not conduct electricity (graphite is an exception).

What it shows: The metal/non-metal split by physical properties alone has real, memorable exceptions — it is a useful first sort, not an exact rule.

Activity 3.8 — What kind of oxide does burning give?

What you do: Burn a magnesium ribbon and dissolve the ash in water; separately burn sulphur powder, collect the fumes in an inverted test tube, and add water. Test both solutions with red and blue litmus.

What you see: The magnesium solution turns red litmus blue (basic); the sulphur solution turns blue litmus red (acidic).

What it shows: Most metals form basic oxides when burnt; most non-metals form acidic oxides — the first chemical-property clue, developed fully in the next lesson.

What you should be able to do

Recognise

Which listed property (lustre, hardness, malleability, ductility, conduction, sonority) a described observation is testing.
A physical-property exception (mercury, gallium/caesium, iodine, graphite, diamond, alkali metals) when named or described.

Explain

Why electric wires are insulated even though the wire itself is metal.
Why sodium and potassium must be handled with tongs, never bare hands.
Why "all metals are hard solids" and "all non-metals are poor conductors" are both false as stated.

State

The meaning of malleable and ductile (a recurring exam question, verbatim from the NCERT exercises).
One metal that is a liquid at room temperature, one that can be cut with a knife, the best conductor of heat, and a poor conductor of heat.

NCERT alignment

This topic corresponds to NCERT Class 10 Science, Chapter “Metals and Non-metals”, sections 3.1, 3.1.1, 3.1.2; activities 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8. Explanations, visuals and worked material here are original.

Quick revision

Metals: lustrous, malleable, ductile, sonorous, good conductors of heat and electricity, solid at room temperature.
Exception — liquid/low-melting metals: mercury (liquid), gallium and caesium (melt in the palm).
Exception — lustrous non-metal: iodine.
Exception — carbon’s allotropes: diamond (hardest natural substance); graphite (conducts electricity).
Exception — soft metals: alkali metals (Li, Na, K) — cut with a knife, low density, low melting point.
Burning magnesium → basic oxide; burning sulphur → acidic oxide — metals give basic oxides, non-metals give acidic oxides, as a general rule.