How can energy value of substrate be determined using a calorimeter?

A calorimeter is tool used to measure the heat substance and the chemical changes or physical changes in a substance or matter. Technically utilized in calorimetry. These calorimeter scans for the heat wave signals in the substance if they have occurred, the alterations and reactions of a certain chemical or matter. Furthermore, we use calorimeter in molar heat solution because we want to be exact in the heat that is in the substance or in this case, solution. Avoiding errors, specifically systematic errors.