Chapter : 2. Is Matter Around Us Pure
Pure Substances
Metals are lustrous (or shiny), and can be polished : The property of a metal of having a shining surface is called metallic lustre (chamak). The shiny appearance of metals makes them useful in making jewellery and decoration pieces
Example. Gold and silver are used for making jewellery because they are bright and shiny. The shiny surface of metals makes them good reflectors of light. Silver metal is an excellent reflector of light.
Metals are generally hard :
Most of the metals are hard. But all the metals are not equally hard. The hardness varies from metal to metal they can not cut with a knife. (except sodium and potassium which are soft metals).
Example. Iron, copper, aluminium.
Metals are usually strong. They have high tensile strength : This means that metals can hold large weights without breaking.
Example. Iron metal (in the form of steel) is very strong having a high tensile strength. Due to this iron metal is used in the construction of bridges, buildings, railway lines, girders, machines, vehicles and chains etc.
Metals are solids at the room temperature :
All the metals like iron, copper, aluminium, silver and gold, etc., are solids at the room temperature. Only one metal, mercury, is in liquid state at the room temperature.
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