Heat and work have signs (positive or negative), and the sign of each depends on whether the system we are considering is gaining or losing energy. In this class, if a process makes the system gain energy, qqq and/or www are positive; if the process makes the system lose energy, qqq and/or www are negative. We can put this information into four formal statements: If heat flows into a system, qqq is positive. If heat flows out of a system, qqq is negative If the surroundings do work on the system, www is positive. If the system does work, www is negative.