21.

Water is a valuable resource. List two ways that you would suggest every family member to save this resource.

List four advantages of vegetative propagation.

Draw a ray diagram to show the path of the reflected ray corresponding to an incident ray which is directed parallel to the principal axis of a convex mirror. Mark on it the angle of incident and the angle of reflection.

Why is Government of India imposing a ban on the use of polythene bags? Suggest two alternatives to these bags and explain how this ban is likely to improve the environment.

What is meant by biodiversity? List two advantages of conserving forest and wild life.

State the meaning of functional group in a carbon compound. Write the functional group present in (i) ethanol and (ii) ethanoic acid and also draw their structures.

 Write the name and general formula of a chain of hydrocarbons in which an addition reaction with hydrogen can take place. Stating the essential conditions required for an addition reaction to occur, write the chemical equation giving the name of the reactant and the product of such a reaction.

Based on the group valency of elements state the formula lot the following giving justification for each :

(i) Oxides of 1st group elements,

(ii) Halides of the elements of group 13, and

(iii) Compounds formed when an element of group 2 combines with, an element of group 16.

(a) Define the following terms :

(i) Valency (ii) Atomic size

b) How do the valency and the atomic size of the elements vary while going from left to right along a period in the modern periodic table?

Draw diagrams to explain the regeneration that takes place in each of the body parts of planaria when its body is cut into pieces. Name any other organism in which a similar process can be observed.