8th Class Science Materials : Metals and Non-metals Notes - Materials-Metals and Non-Metals

Materials - Metals and Non-Metals

·                     Materials can be classified into metals and non-metals.

·                     Metals can be distinguished from non-metals on the basis of their physical and chemical properties.

·                     Physical properties of metals

§  Metals are hard, lustrous, malleable, ductile, sonorous and good conductors of heat and electricity. Iron, copper, aluminum, calcium and magnesium are some examples of the metals.

·                     Metals are generally hard but the metals like sodium and potassium are soft and can be cut with a knife. Similarly, mercury is the only metal which is found in liquid state at room temperature.

·                     Chemical properties of metals

§  Metals on burning in the presence of oxygen, produces metal oxides which are basic in nature.

§  Metals on reaction with water produce metal hydroxides and hydrogen gas.

§  Metals on reaction with acids produce metal salts and hydrogen gas.

§  Some metals react with bases to produce hydrogen gas.

§  More reactive metals displace less reactive metals from their compounds in aqueous solutions. This type of reaction is called displacement reaction.

·                     Physical properties of non-metals

§  Non -metals are soft and dull in appearance, break down into powdery mass on tapping with hammer, are not sonorous and are poor conductors of heat and electricity.

·                     Diamond which is the hardest known element on the earth is a non-metal.

·                     Chemical properties of non-metals

§  Non-metals react with oxygen to produce non- metallic oxides which are acidic in nature.

§  Non-metals generally do not react with water.

§  Non-metals do not react with acids.

·                     Metals and non-metals are used widely in everyday life.