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: Metal can be beaten into thin sheets. This property of metals is called malleability.
Ductility: Metals can be pulled to make thin wire. This property of metals is called ductility.
Sonority: Metals produce a typical ringing sound when hit by something. This property is called sonority or sonorousity.
|Conductivity||good conductors of heat and electricity||Bad conductor|
|Lustrous||have metallic shine||are usually dull|
|Physical State||Most are solid at room temperature||available in all the three states of matter|
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. The green coat is because of formation 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
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.
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.
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