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What are the differences between metals and non-metals?

Class 7 ScienceNCERT chapter: The World of Metals and Non-metalsइसे हिंदी में पढ़ें

Exam-ready answer

Metals are usually shiny (lustrous), hard, malleable (can be beaten into sheets), ductile (can be drawn into wires), sonorous (ring when struck) and good conductors of heat and electricity. Non-metals are usually dull, brittle, non-sonorous and poor conductors. Metal oxides are basic, while non-metal oxides are acidic. Examples: iron, copper and aluminium are metals; sulphur, carbon and oxygen are non-metals.

Explanation

Compare an iron nail, a copper wire and aluminium foil with a piece of coal and some sulphur powder. Freshly rubbed metals shine, a property called lustre, while coal and sulphur look dull. When a metal is hammered it flattens into a sheet; this property is malleability, which is why aluminium foil and the silver foil on sweets can be made. Coal or sulphur breaks into pieces instead, so they are brittle.

Metals can be drawn into thin wires, a property called ductility. Copper and aluminium are used for electrical wires because metals also conduct electricity and heat well, and cooking pans are made of metal for the same reason. Metals produce a ringing sound when struck, so they are sonorous and are used for school bells. Non-metals generally lack these properties, with exceptions: graphite conducts electricity and iodine is shiny.

Metals and non-metals also differ chemically. A burning magnesium ribbon forms magnesium oxide; its solution in water turns red litmus blue, so metal oxides are basic. Burning sulphur forms sulphur dioxide, whose solution in water turns blue litmus red, so non-metal oxides are acidic. Most metals are solids at room temperature except mercury, a liquid; non-metals may be solids (carbon, sulphur), a liquid (bromine) or gases (oxygen, nitrogen).

Points to remember

  1. Metals: lustrous, generally hard, malleable, ductile, sonorous, good conductors of heat and electricity.
  2. Non-metals: dull, brittle when solid, non-sonorous, poor conductors of heat and electricity.
  3. Metal oxides are basic (turn red litmus blue); non-metal oxides are acidic (turn blue litmus red).
  4. Exceptions: mercury is a liquid metal; sodium and potassium are soft metals; graphite conducts electricity; iodine is lustrous.
  5. Metals: iron, copper, aluminium, gold. Non-metals: carbon, sulphur, oxygen, nitrogen.

Exam tip

Write the answer as a table with properties in the first column — lustre, hardness, malleability, ductility, sonority, conductivity and nature of oxide — and give one example in each column.

Questions students also ask

Why are bells made of metal?
Metals are sonorous, which means they produce a ringing sound when struck. Non-metals and materials such as wood produce only a dull thud. That is why school and temple bells are made of metal.
Which non-metal conducts electricity?
Graphite, a form of carbon used in pencil leads, conducts electricity even though carbon is a non-metal. That is why a pencil lead placed across the gap of an electric tester makes the bulb glow.
What is the difference between malleability and ductility?
Malleability is the property of a metal by which it can be beaten into thin sheets, like aluminium foil. Ductility is the property by which it can be drawn into thin wires, like copper wire. Both are typical properties of metals.

Chapter labels help you find the topic in your textbook. Check your own edition: chapter names and order can change. These are Know.it explanations, not official NCERT solutions.