Question

Camphor disappears without leaving any residue. Explain?

Answer 1

To answer this question, you should recall the concept of sublimation. Sublimation is defined as the changing of a substance directly from the solid to the gas state, without passing through the liquid state.

Complete step by step answer:
Sublimation process is endothermic and occurs at a temperature and a pressure lower than the substance's triple point in its phase diagram. This pressure is the lowest pressure at which the substance can exist as a liquid. The opposite or reverse of sublimation is deposition, in which a substance passes directly from a gas to a solid phase.
Evaporation is considered as the transition from liquid to gas if it takes place at a temperature lower than the boiling point of the liquid, and the process of boiling only occurs at the boiling point. There is no such distinction within the solid-to-gas transition, it is always described as sublimation. Camphor disappears after some time as its surface gains kinetic energy and directly gets converted into gas.
Hence, when camphor is given heat, it gets converted into gas and disappears, without leaving any residue.

Note:
Sublimation requires a specific amount of energy to take place. This energy is known as sublimation energy. Sublimation molar heat can be defined as the amount of energy that must be applied to one mole of solid-phase at constant pressure to convert it directly into the gas phase. The best example of sublimation is dry ice which is a frozen form of carbon dioxide. Upon exposure of this dry ice to air, it is observed that dry ice directly changes its phase from solid-state to gaseous state which is visible as fog. Frozen carbon dioxide in its gaseous state is more stable than in its solid-state.