關於潛熱和蒸發

1. 究竟潛熱如何增加勢能呢??

The collision between molecules to maintain a separation between them is applicable in gases in which molecules are free to move. In solids and liquids, the (translational) movement of molecules is limited.

Hence, in solids and liquids, the molecular seaparation can be maintained is because of the thermal agitation of molecules, i.e. vibrational motion. This is just like two balls (representing molecules) connected by an elastic spring (represents intermolecular force). As long as the balls are kept in vibration, the spring would not shrink to its natural length.

When an object changes state, either from solid to liquid or from liquid to gas, the supplied energy is first used to increase the thermal agitation of molecules, and so the temperature increases. But at the same time, the molecular separation also increases as a result of increased thermal agitation. At the temperature of state change, the thermal agitation is strong enough to break the bonding (the intermolecular attractive force) between molecules. The molecules are thus moving more freely, thus possessing more potential energy than before. The latent heat is therefore the energy supplied to break the bonding between molecules.

2.關於蒸發(evaporation),所需的潛熱跟boiling是一樣的嗎?

Apparently it is. Water molecules at the gas state at the same temperature all possess the same amount of mean energy. You could not differenitate a water molecule that comes from evapourization with one that comes from boiling.