if q is positive for a system
[5.4]. When heat is transferred from the surroundings to the system, q has a positive value. Likewise, when work is done on the system by the surroundings, w has a positive value (Figure 5.6). In other words, both the heat added to the system and the work done on the system increase its internal energy.onversely, both the heat lost by the system to the surroundings and the work done by the system on the surroundings have negative values; that is, they lower the internal energy of the system. The relationship between the signs of q and w and the sign of E is presented in Table 5.1.