Calorie © Eric R. Pianka The amount of heat required to raise one cubic centimeter of water by exactly one degree Celsius is defined as a calorie which is a unit of heat energy. We also define 100 oC as the temperature at sea level of the boiling point of water (when it changes from the liquid to gaseous state). The temperature at its freezing point, when water changes from the liquid state to the solid state (ice), is defined as 0o C. Links: USGS on water Wikipedia entry on water Wikipedia entry on the water molecule See also sewage