Question

Give reasons for the following:
(a) Aluminium foils are used to wrap food items.
(b) Immersion rods for heating liquids are made up of metallic substances.
(c) Copper cannot displace zinc from its salt solution.
(d) Sodium and potassium are stored in kerosene.

Answer 1

a) Aluminium is one of the less reactive metals, so it does not react with food items and does not alter the taste. Moreover, being a metal, aluminium is highly malleable and can be made into very thin foils which are perfect for wrapping food.

b) Immersion rods for heating liquids are made up of metallic substances because metals are good conductors of heat and electricity. The immersion rod needs an electric supply to get heated and in turn to heat liquids.

c) Copper is less reactive than zinc. This can be confirmed from the electrochemical or activity series in which $Zn$ has a lower reduction potential than $Cu$. This means $Zn$ is more reactive than $Cu$. This is the reason, copper cannot displace zinc from its salt solution.

d) Sodium and potassium are highly reactive metals. If kept in open, they readily react with oxygen in the atmosphere. The reaction is so quick that sodium and potassium easily catch fire when exposed to air. To prevent accidental fire, they are stored in kerosene.