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.