What is Heat?

We now have several scales for measuring temperature, but first let's ask, “Is temperature the same as heat?” If I add heat to a pot of water, the water's temperature will go up. But if I have a small pot of cold water and a large pot of cold water, will their temperatures go up the same amount if I add the same amount of heat to each? No. Heat is more than just the temperature of the material. It also depends on how much of the material there is and what the material is made of.

Kinetic theory of matter proposes that heat is a measure of the internal kinetic energy (microscopic jiggles) of the molecules and atoms making up the substance. If, when I touch a stove, my hand is burned (heat was transferred to my hand), then I can deduce that the temperature (and kinetic energy of the molecules or atoms) of the stove was higher than the temperature (and kinetic energy of the molecules or atoms) of my hand. Temperature indicates when heat will be transferred but does not tell the whole story as to how much heat energy is stored in a substance.

The specific heat, c,( in cal/gCo) of a material is a number which gives us an idea of how much heat is needed to raise the temperature of one gram of the material one Celsius degree. This is a property of materials which explains why some foods remain hotter longer than others. You are more likely to burn your tongue on the filling of a hot apple pie than the crust. This tells you experimentally that the apple pie filling has a greater specific heat (it takes more heat to bring one gram of it to a given temperature or you must remove more heat to drop the temperature of one gram) than the crust. Water has one of highest specific heats at 1 cal/gCo. One gram of water is able to absorb and hold more heat than other liquids. This is why before the advent of electric blankets and heating pads, the use of hot water bottles was common. It also means that when water is cold, it can absorb more heat as it warms up. This is why we use ice in our coolers to keep our food and drinks cold, and cold water circulating in tubing is often used to cool many things including an astronaut in his/her space suit. This is also the main reason why the outdoor temperature near bodies of water is moderated. It tends to be cooler in summer and warmer in winter near the beach.
 
Example - How much heat must be added to 5.0 kg of water to increase its temperature by 20 Co? (the specific heat of water is 1.0 cal/gCo = 1.0 kcal/kgC°)

  
or 100 of the Calories that we speak of when we diet, because one diet Calorie is equal to one kilocalorie.