Specific Heat:

Pure liquid water requires 1 calorie per gram (1 cal/g) to cool it down or warm it up by 1°C (provided it is not at the freezing /melting temperature or the condensation/vaporization temperature.) Though, what about alcohol, oil, or salt water? What about solids like steel or wood? What about gases like air? It is not thus simple then. Certain, fixed quantity of heat energy will raise or lower the temperatures of fixed masses of several substances more than others. Several matters take more than 1 cal/g to get hotter or cooler by 1°C; some matter takes less. Pure liquid water takes accurately 1 cal/g to warm up or cool down by 1°C merely since this is the substance on which the definition of the calorie depends. It is one of those things scientists term a convention.

Assume that we have a sample of several mysterious liquid. Let's say substance X. We measure out 1 gram (1.00 g), precise to three significant figures, of this liquid by pouring few of it into a test tube located on a laboratory balance. Then we transfer 1 calorie (1.00 cal) of energy to the substance X. Assume that, as an outcome of this energy transfer, substance X raises in temperature by 1.20°C? Off course, substance X is not water since it behaves in a different way from water whenever it receives a transfer of energy. In order to increase the temperature of 1.00 g of this material by 1.00°C, it takes somewhat less than 1.00 cal of heat. To be accurate, at least insofar as we are permitted by the rules of significant figures, it will take 1.00/1.20 = 0.833 cal to increase the temperature of this material by 1.00°C.

Now assume that we have a sample of the other material, this time a solid. Let us call it substance Y. We cut a chunk of it down until we have a piece which masses 1.0000 g, accurate to five significant figures. Again, we can employ our trusty laboratory balance for this reason. We transfer 1.0000 cal of energy to substance Y. Assume that the temperature of this solid goes up by 0.80000°C. This material allows heat energy in a manner distinct from either liquid water or substance X. It takes a slight more than 1.0000 cal of heat to raise the temperature of 1.0000 g of the material by 1.0000°C.

Computing to the permitted number of significant figures, we can establish that it takes 1.0000/0.80000 = 1.2500 cal to increase the temperature of this material by 1.0000°C.

We are onto something here: a special property of matter known as the specific heat, stated in units of calories per gram per degree Celsius (cal/g/°C). Let's say that it takes c calories of heat to increase the temperature of accurately 1 gram of a substance by accurately 1°C. For water, we already know that c = 1 cal/g/°C, to though many significant figures we want. For substance X, c = 0.833 cal/g/°C (to three significant figures), and for substance Y, c = 1.2500 cal/g/°C (to five significant figures).

Alternatively, c can be expressed in kilocalories per kilogram per degree Celsius (kcal/kg/°C), and the value for any certain substance will be similar. Therefore, for water, c = 1 kcal/kg/°C, to though many significant figures we desire. For substance X, c=0.833 kcal/kg/°C (to three significant figures), and for substance Y, c = 1.2500 kcal/kg/°C (to five significant figures).