CBSE Class 8 Science Chapter 4 Materials : Metals and Non-Metals Revision Notes
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Metals are opaque and lustrous elements which are good conductors of heat and electricity.
Example: Iron, copper, zinc.
Properties of metals
▪ Malleable – ability to be beaten into sheets, e.g. aluminum and silver foil.
▪ Ductile – ability to be drawn into wires e.g. copper wires.
▪ Lustrous – ability to shine, e.g. gold and silver.
▪ Sonorous – makes a ringing sound when strikes with a hard surface, e.g. bells.
▪ Hard in nature, e.g. iron, lead
▪ Exception – (Sodium and potassium are soft metals and can be cut with a knife).
▪ Good conductors of heat and electricity, e.g. copper.
▪ Mostly solids
▪ Exception – (Mercury is the only liquid metal).
The elements that do not have the properties of metals are known as non-metals. Non-metals are widely present in the earth’s crust and atmosphere. All oceans and water bodies have an abundance of these elements. Examples: Carbon, hydrogen, and oxygen.
Properties of Non-Metals
▪ Non-malleable – cannot be made into sheets e.g. sulphur breaks into powdery mass when beaten with a hammer.
▪ Non-ductile – cannot be made into wires.
▪ Non-lustrous/dull, e.g. coal.
▪ Non-sonorous – cannot make a ringing sound when struck with any object.
▪ Soft, break easily, e.g. sulphur, pencil lead.
▪ Poor conductors of heat and electricity, e.g. phosphorus
▪ Exception – (Graphite is a good conductor of heat and electricity).
▪ It can be solid (sulphur), liquid (bromine), or gaseous (oxygen).
CBSE Class 8 Science Chapter 4 Materials: Metals and Non-Metals Revision Notes PDF