Question

Neither q nor w is a state function but q+w is a state function. Why?

Answer 1

the symbols q, w and$\Delta$U(q+w) in thermodynamics are symbols to heat , work and internal energy respectively.

Complete step by step solution:
In thermodynamics the universe is made of system and surrounding where all the observations are made is system and everything except system in universe is surrounding. Several types of systems are classified on the basis of movement of matter and energy in or out the system
- Open system
- Closed system
- Isolated system
The state of the system is further described by various properties such as pressure, volume, temperature and composition. It is specified by state functions or state variables as their values depend only on the state of the system and not on how it is reached. $\Delta$U or internal energy is a quantity which represents the total energy of the system .It may be chemical, electrical or other energies, the sum of all these is the energy of the system . This energy is internal energy which may change when:
- heat passes into or out of the system (q)
- work is done or by the system(w)
- matter enters or leaves the system
q and w both are path dependent in nature, that is their value is not just defined by the initial and final position but by the path followed as well and it can vary on how the change is carried. q+w=$\Delta$U gives the first law of thermodynamics and is path independent that means it will only depend on the initial and final state.

Note: For adiabatic system q=0