Physical and Chemical changes
PHYSICAL CHNAGES:-
· A change is called physical change when a substance undergoes a change in its physical properties such as shape , size, color & state of matter. and .
· Properties such as shape, size, colour, and state of substance are called physical properties.
· A physical change is generally reversible
· In physical change where no new substance are formed.
· The chemical properties of the substance doesn’t change.
CHEMICAL CHNGES:-
· A change is called chemical change when a substance undergoes a change in its chemical propertiesand form a new substance .
· The chemical change is irreversible.
· During chemical change heat, light, sound or gas may produce.
· A change in colour or smell may occur.
· Example :- Burning of magnesium ribbon, Changing milk into curd, Ripening of fruits.
Burning of magnesium ribbon:-
Magnesium (Mg) + Oxygen (O2) → Magnesium oxide (MgO)
Magnesium oxide (MgO) + Water (H2O) → Magnesium hydroxide [Mg(OH)2]
Rusting:-
· The chemical formula for rust is Fe2O3 and is commonly called ferric oxide or iron oxide.
· Rusting is harmful since the object made of iron like gates, pillars, chains, bridges etc. get rusted which results in eating away the metal which finally gets converted into powder.
· To prevent rusting paint is applied on the surface of iron.
· By galvanization (zinc coat) rusting can be prevented.
