Specific heat is a physical measurement of a substance s ability to hold heat. Specific heat is defined as the amount of energy that must be absorbed in order to increase the temperature of 1 gram of substance by 1 degree centigrade. Water has a specific heat of 1.00 calorie per gram degree. Compare to benzene at 0.406 calorie per gram degree. Again, the answer has to do with its hydrogen bonding capabilities.
Temperature is a measure of the motion of molecules.
High temperatures mean lots of motion. In order to get the water molecules moving around, you have to disrupt some of the hydrogen bonding which is holding it together. These kinds of physical constants are used to determine heat flow. We can use this equation to determine what temperature change will occur as heat is added or how much heat is required to enact a temperature change. The water has to be heated in the water heater.