Melting point of ice

CONCEPT:

• Melting and Melting Point: The process of change of state from solid to liquid is called melting.
• The temperature at which solid starts to liquefy is known as the melting point of that solid.
• The melting point of a substance at atmospheric pressure is called a normal melting point.

EXPLANATION:

Variation of melting point with pressure:

• For those substances which contract on melting (e.g. water), the melting point decreases with pressure.
• The reason is that, pressure helps to shrink and hence melting. Most substances expand on melting. (e.g. sulpher)
• An increase of pressure opposes the melting of such substances and their melting point is raised.
• The melting point of ice decreases with an increase in pressure (as ice expands on solidification).

• For most of the materials, the melting point increases with increase in pressure but ice is an exception for that.