Question

Give scientific reasons.

a. Foam accumulates on the surface of 'dal' kept for a long time in summer.
b. Why are naphthalene balls kept with clothes to be put away?

Answer 1

a. Foam accumulates on the surface of 'dal' kept for a long time in summer due to trapping of water vapours in the saponins of dal. These foams also provide a good medium for microbial growth.

b. Naphthalene balls are kept with clothes to put away because naphthalene repels the insect larvae that feed on clothes fibres. Naphthalene shows sublimation, it slowly dissolves in the air and creates repulsive fumes for the larvae.