Question

Give reasons.
(a) While purchasing canned food, its expiry date should be checked.
(b) An iron article should be given a coat of paint
(c) A wooden article should be polished.
(d) Copper and brass utensils should be tinned.
(e) A dry handkerchief gets wet at once on dipping in water, but it takes long for a wet handkerchief to dry.

Answer 1

a. While purchasing canned food their expiry date should be checked because an expiry date indicates that for how long a canned food is safe for consumption. Canned foods with expired dates are not considered worth consumption as they could affect your health. They might get contaminated with microorganisms like bacteria or may have no nutritional value left after its expiration.

b. Iron articles often undergo rusting resulting in the formation of a reddish brown layer on its surface. Rusting is caused by the exposure of iron to the air and water in the surroundings. An iron article which is coated with a paint prevents the interaction of iron with the surrounding air and water and thus protects it from rusting.

c. A wooden article should be polished because it protects the wooden article from sunlight and all other external conditions and also it reduces the probability of wooden mites damaging the furniture.

d. Copper and brass materials also undergo corrosion resulting in the formation of a greenish layer on this surface. When the surface of copper/ brass comes in contact with air or water, it results in corrosion and to prevent this, the process of tining is used. In this process copper and brass articles are coated with tin.

e. A dry handkercheif gets wet at once because it quickly absorbs the water in which it is dipped. However, it takes longer for a wet handkerchief to dry because the water needs to evapourate from the handkerchief. Evaporation is a slow process which is dependant on other factors as well like relative humidity.