Physical properties of metals and non-metals
Metals are usually shiny, hard, malleable, ductile and good conductors. Non-metals are usually dull, brittle and poor conductors. Learn the exceptions: they are asked often.
Metals vs non-metals
| Property | Metals | Non-metals |
|---|---|---|
| Lustre (shine) | Lustrous: shiny when freshly cut or rubbed | Dull |
| Hardness | Usually hard | Usually soft, if solid |
| Malleability and ductility | Malleable and ductile | Brittle: break into pieces |
| Heat and electricity | Good conductors | Poor conductors |
| Sound | Sonorous: ring when struck | Not sonorous |
| State at room temperature | Solids (except mercury) | Solids or gases (bromine is a liquid) |
| Melting point | Usually high | Usually low |
Exceptions to remember
| Exception | Why it is special |
|---|---|
| Mercury | A metal that is liquid at room temperature |
| Sodium, potassium, lithium | Metals so soft they can be cut with a knife; low density and low melting point |
| Gallium, caesium | Metals with such low melting points that they melt on your palm |
| Lead, mercury | Metals that are poor conductors of heat |
| Iodine | A non-metal that is lustrous |
| Graphite (a form of carbon) | A non-metal that conducts electricity |
| Diamond (a form of carbon) | A non-metal that is the hardest natural substance, with a very high melting point |
Simple tests you can do
- Lustre: rub a piece of iron, copper or aluminium with sandpaper. The fresh surface shines.
- Malleability: strike a piece of zinc or aluminium with a hammer. It flattens, while a piece of coal breaks.
- Conduction of heat: fix a little wax to one end of an aluminium or copper wire and heat the other end. The wax melts.
- Conduction of electricity: put a metal in a circuit with a bulb. The bulb glows.
- Sonority: drop a metal coin on the floor. It rings, which is why bells are made of metal.
Why metals are used as they are
Cooking vessels are made of aluminium, copper and steel because they conduct heat well. Electric wires are made of copper and aluminium because they conduct electricity well. The wires are covered with PVC or rubber, which are poor conductors, for safety. Silver can be beaten into the thin varq used on sweets.
The thin silver varq on kaju katli shows how malleable silver is. Temple bells and school bells are made of metal because metals are sonorous.
2 marks: “Give reasons: (i) the copper wires in a house are covered with PVC; (ii) temple bells are made of metal, not wood.” (i) PVC is a poor conductor of electricity, so it prevents electric shocks. (ii) Metals are sonorous: they make a ringing sound when struck.
2 marks: “Name (i) a non-metal that is lustrous, and (ii) a non-metal that conducts electricity.” (i) Iodine. (ii) Graphite, a form of carbon.
3 marks: “Differentiate between metals and non-metals on the basis of any three physical properties.” Metals are lustrous, non-metals are dull. Metals are malleable and ductile, non-metals are brittle. Metals are good conductors of heat and electricity, non-metals are poor conductors.
Metals are LMDCS: Lustrous, Malleable, Ductile, Conductors, Sonorous. Exceptions: "Mercury flows, sodium slices, gallium melts in hand; iodine shines, graphite conducts, diamond is hardest."