Melting

or Fusion, passing from a solid to a liquid state. In theory, any solid may be turned into a liquid if heated sufficiently. Some solids, as ice, pass into a liquid abruptly; others, like iron, soften and yield before melting. Most substances increase slightly in volume as they melt, as may be noted by the fact that the unmelted portion lies at the bottom of the crucible. Cast iron, ice, and bismuth are exceptions. They float, showing that they shrink as they melt. As is well known, ice is lighter than water. Most metals melt at a higher temperature if subjected to increased pressure, but pressure assists the melting of ice and cast iron. Under ordinary or the same conditions of pressure, a substance always melts at the same temperature, and remains at that temperature during the process of melting. Ice, for instance, never fails to melt at 0 deg. C. or 32 deg. F., and, though thrown into boiling hot water, its temperature remains at 0 deg. C. or 32 deg. F. until it is entirely melted.