which says simply that a change in the total energy of a system may result from work (\(W\)) or from “heat exchange” (\(Q\)). “Heat,” in physics usage today, is simply what we call the thermal energy ...which says simply that a change in the total energy of a system may result from work (\(W\)) or from “heat exchange” (\(Q\)). “Heat,” in physics usage today, is simply what we call the thermal energy that is directly transferred from one object to another, typically by contact; the convention used for this term is the same as for the work term, that is, \(Q\) is positive if thermal energy flows into the system and negative if thermal energy leaves the system.
