The region just above the light bulb is warmest due to the phenomenon of convection.
Explanation:
In the given case, as Xavier places his hands close to a light bulb, he feels that some of the regions around the light bulb are warmer in comparison to others. This takes place due to the phenomenon known as convection because of which the region directly above the light bulb gets warmest in comparison to the other regions.
Convection refers to the transfer of heat with the help of mass movement of fluid like air, and the phenomenon takes place above a hot surface as hot air expands, becomes less dense, and elevates. This thing can be supported by the ideal gas law.
The method of distillation can be used to separate the two liquids, if their boiling point is known. The liquid with lower boiling point will be evaporated and its vapours will be captured, while the liquid with higher boiling point will remail in the container in the liquid state.