Assume it is mostly water and use the specific heat of water in the equation above. In a bomb calorimeter the reaction mix, called the system, is surrounded by a jacket of water, which is the system s surroundings . In the reaction heat is transferred from the system to its surrounding. Method 3 . There is a table of these enthalpies for may common substances in the appendices of your text.
Liquid water is in a lower energy state than water vapor.
Therefore, these are endothermic processes. In the body, the metabolism of simple sugar is, overall, the same reaction, although it takes over 25 steps when done biochemically. Either way, the energy available is the same. Using Hess law to calculate the enthalpy change of a reaction that is hard to measure directly.