An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be

Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).

Why is sodium kept immersed in kerosene oil?

Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it,as shown in the figure below.
$(a)$ What will be the action of the gas on
$(i)$ dry litmus paper?
$(ii)$ moist litmus paper?
$(b)$ Write a balanced chemical equation for the reaction taking place.

What are amphoteric oxides? Give two examples of amphoteric oxides.

What are alloys?