Take about 20 mL of castor oil in a beaker. Add 30 mL of 20% sodium hydroxide solution. Heat the mixture with continuous stirring for a few minutes till the mixture thickens. Add 5-10 g of common salt to this. Stir the mixture well, allow it to cool, soaps is obtained. 

(a) Why do we use common salt to make soap?
(b) What will happen if you will add the above made soap solutions to the following test tubes A, B, and C.
(c) Can we use potassium hydroxide instead of sodium hydroxide.

A hydrocarbon compound A is active ingredient of wine and cough syrup. A on oxidation with acidified K₂Cr₂O₇ forms compound B. Identify the compound A and B and write the chemical equations involved.

List four changes which help us to determine whether a chemical reaction has taken place

Three organisms ate food in the form of glucose and the end products after respiration are:
a - ethanol + CO₂
b - CO₂+H₂O 
c - Lactic acid + water
Explain how is this possible?

Why do we prefer a convex mirror as a rear view mirror in vehicles?

The atomic number of three elements X, Y and Z are 5, 7 and 10 respectively.
(a) Which element belongs to group IIIA?
(b) To which period do these elements belong?
(c) Which element belongs to VA?
(d) Which element belongs to zero group?

What is the probable formula of the oxide of the Silicon?

An organic compound 'A' which is used as antifreeze has the molecular formula C₂H₆O. On addition, it gives a compound 'B' which baking soda solution. Identify the compound A and B.

(a)What prevents the entry of food into trachea while swallowing?
(b)Why rate of breathing is faster in aquatic animals as compared to terrestrial animals?

A substance 'A' displaces 'B' from its solution in water. It is called displacement reaction. What other chemical name can be given to such type of reactions? Explain with an example.