Class 8 Science
Metals: Metals are lustrous, sonorous, ductile, and are good conductor of heat and electricity.
Non-metals: Non-metals are no-lustrous, non-sonorous, non-ductile, and are bad conductor of heat and electricity.
|Malleability||Metals are malleable, i.e. they can be beaten into thin sheets.||Non-metals are not malleable.|
|Conductivity||Metals are good conductors of heat and electricity.||Non-metals are bad conductors of heat and electricity. (exception: graphite)|
|Ductility||Metals are ductile, i.e. they can be drawn into thin wires.||Non-metals are not ductile.|
|Sonorous||Metals are sonorous, i.e. they produce a typical metallic sound when hit with something.||Non-metals are not sonorous.|
|Lustrous||Metals have metallic shine; called lustre.||Non-metals are usually dull. (exceptions: diamond and graphite)|
|Physical State||Most of the non-metals are available as solid at room temperature; except mercury. Sodium and potassium are so soft that they can be cut with knife.||Non-metals are available in all the three states of matter.|
Chemical Properties of Metals and Non-metals
Reaction with Oxygen
Metals react with oxygen to form metallic oxides. Metallic oxides are basic in nature.
Example: Iron reacts with oxygen and moisture to form iron oxide. Iron oxide is brown in colour and is commonly known as rust.
Fe + O2 + H2O → Fe2O3
Example: Magnesium reacts with oxygen when it is burnt and forms magnesium oxide.
Mg + O2 → 2MgO
Example: When copper is exposed to moist air for a long time, it acquires a greenish coating; because of formation of copper hydroxide and copper carbonate. The green coat is a mixture of copper hydroxide and copper carbonate.
2Cu + H2O + CO2 + O2 → Cu(OH)2 + CuCO3
Non-metals also react with oxygen to make oxides. Oxides of non-metals are acidic in nature.
Example: Sulphur reacts with oxygen when it is burnt. It forms sulphur dioxide.
S + O2 → SO2
When sulphur dioxide is dissolved in water, it forms sulphurous acid.
SO2 + H2O → H2SO3
Reaction with water
Some metals react vigorously with water, while some others do not react at all with water.
Example: Sodium is a highly reactive metal and reacts vigorously with water. This is a highly exothermic reaction. During this reaction; sodium catches fire because of too much heat being evolved. Due to this, sodium is stored in kerosene to prevent accidental fire.
- Iron reacts slowly with water.
- Copper does not react with water but reacts with steam.
- Silver and gold do not react with water at any temperature.
Usually, non-metals do not react with water; but some non-metals react vigorously with air. Such non-metals are stored in water to prevent their reaction with air. For example; phosphorus is stored in water to prevent its reaction with air.