Why is that latent heat of vaporisation is greater than specfic latent heat of fusion to most substance?
To understand the answer to this question, it is important to understand what happens during vaporization and fusion. In vaporization, the molecules of the substance have to separate a great deal against the force of attraction between the molecules of the substance in liquid state. The distances between the molecules in vapor state are much larger than their distances in the liquid state. In comparision, such separation between molecules in fusion,i.e., conversion from solid to liquid state is much less. Hence, the work done against the force of molecular attraction in vaporization is much larger due to larger separation as compared to fusion in which case the separation is less against more or less the same force. This is the reason for the heat of vaporization to be more than the heat of fusion. It is the heat energy which provides for this work done. I would like to add here some interesting observation. As the pressure increases, volume of vapor reduces which brings the molecules
