(i) Zinc is placed above iron in the reactivity series. It has therefore reduced Fe²⁺
ions to Fe.
(ii) Zn(s) + Fe²⁺⟶Fe(s) + Zn²⁺(aq)
(iii) One should be very careful in selecting container for storing certain chemicals.

(i) Intermixing of particles 9ases or liquids spontaneously is called diffusion. Liquids diffuse at a slower rate as compared to gases.
(ii) Ammonia gas will reach first to a person in the centre of the laboratory because it is lighter than hydrochloric acid. 
(iii) The phenomenon of diffusion of gases is very useful in daily life. As a result of diffusion, the poisonous effect of the gases gets slowly diluted

(i) In solid form they are (anions & cations) closely packed, that is why they are not able to move.
(ii) In water they aquire mobility and can conduct electricity.
(iii) By this property these compounds can be applied in electroplating of all types of cells.

(i) Atomic no. of the element is the basis of classification of modern periodic table.
(ii) Students can be divided on the basis of their grasping capacity in class.
(iii) Classification can be applied in class and special attention can be paid to the students who are weak in studies.

(i) According to Heisenberg, it is not possible to measure simultaneously the position and the momentum of a microscopic particle with absolute accuracy.
(ii) It has significance for microscopic particles. After his principle both wave and particle nature were considered and quantum mechanics was developed.
(iii) It has no impact on our daily life. It applies only to the moving microscopic particles which we cannot see with our eyes.