Question

Why is the sign of work and heat important and how does it affect free energy change, ΔE.

Answer 1

The signs of work and heat are very important because they give the direction of the process being done. According to the convention followed in Chemistry, if the work is done on the system then it is positive and if done by the system it is negative.

Similarly, if the heat is given to the system, then it is positive and if given by the system, it is negative.

Based on these signs of heat and work for a given system, the change in internal energy(ΔE), will become positive, negative or equal to zero depending on them.