What does the symbol Delta S represent?

The symbol Delta S represents the change in entropy, making it the correct answer. Entropy is a fundamental concept in thermodynamics that measures the degree of disorder or randomness in a system. When a process occurs in a chemical or physical system, it can be accompanied by a change in the system's entropy, which is denoted as Delta S.

Positive changes in entropy indicate that the system has become more disordered, while negative changes indicate that the system has become more ordered. Understanding entropy and its changes is crucial for predicting the spontaneity of reactions and the direction in which processes will naturally occur, according to the second law of thermodynamics.

The other choices refer to different thermodynamic quantities: change in energy relates to the overall energy of the system, change in enthalpy signifies heat changes at constant pressure, and change in temperature measures changes in thermal energy. Each of these has its own distinct symbol and significance in thermodynamic processes.