Heat & State property

[Grace Chen 3F]

Dr. Lavelle said in today's lecture that heat is not a state property, but 'heat under constant pressure' is a state property. I don't really get the difference, can someone explain to me?

[Fiona H 2E]

Heat itself is not a state function because a state function depends only on the final and initial state of the system. It does not depend on how we got from initial to final state. Heat is the energy transferred between the system and the surroundings during some process. The amount that transfers does depend on how the process happens and is therefore not a state function.

[madison_bang_1L]

We can treat heat as a state function because 'heat under constant pressure' is the definition of enthalpy. He mentioned towards the beginning of the lecture that if an open system is used, pressure is constant, and therefore no energy is being transferred as work. Therefore, q_p = delta H (also known as enthalpy). Enthalpy is a state function.

[elliemehrara]

Heat can be thought of as a state function under constant pressure because this is considered enthalpy which is a state property. Heat is not a state property itself because it is the energy transferred between systems. This transfer of energy is dependent on the path taken, therefore making heat not a state variable.