Final answer:
A fume is produced by the condensation of vaporized solids, often from processes such as welding, whereas vapour originates from the evaporation of liquids. Fumes consist of fine particles, while vapour is a gaseous state which can condense back into liquid upon cooling.
Step-by-step explanation:
The difference between a fume and a vapour is primarily based on their origin and the physical state of the substance before it becomes airborne. Fumes are typically small, solid particles that arise from the condensation of vaporized solids, often as a result of chemical reactions or high temperatures, such as welding or smelting. In contrast, vapours come from the evaporation of liquids. For instance, when a liquid evaporates at a temperature below its boiling point, it turns into a gas without first becoming solid. This gas may then be called a vapour. It is also important to note that upon contact with cooler air, vapour can undergo condensation, transforming back into a liquid form.
Vapourization and condensation are important concepts in understanding the difference between fume and vapour. Vaporization is the process in which a liquid is converted to a gas, and evaporation is specifically the conversion of a liquid to its vapor below the boiling temperature of the liquid. Conversely, condensation is the change of state from a gas back to a liquid. Fumes, on the other hand, are not directly related to the state change between liquid and gas but involve the sublimation or chemical transformation of a solid into a gas, followed by the formation of solid particles upon cooling.