the amount of heat required to cause a change of phase from solid to liquid, or the heat released when the phase change is from liquid to solid; in the case of melting snow, the phase change from ice to water requires a significant amount of heat—160 times that required to raise the temperature of the same amount of ice by just 1 degree Celsius; until the required amount of heat is supplied to completely melt all of the ice being considered, no further increase in temperature will occur.