Question

Which of the following does not have a fixed melting point/boiling point ?

(a) gold (b) ethanol (c) air (d) oxygen

Answer 1

The boiling point of a substance is where the liquid phase changes into gas phase. The melting point of a substance is where the solid phase changes into the liquid phase. Since air is a mixture of gases, so, all the different gases have different melting and boiling points. So, air has no boiling point and it also has no melting point. Gold is a metal, ethanol is a type of alcohol and oxygen is type of gas which have only atoms of oxygen. Hence, remaining all three have fixed substances and therefore have fixed melting/ boiling point. But air does not.
option c is correct