Which of the following describes a form of energy identified by temperature difference or a change of state?

Heat is a form of energy that is transferred between systems or objects with different temperatures, moving from the hotter object to the cooler one until thermal equilibrium is reached. This transfer can occur in various ways, such as conduction, convection, and radiation. Additionally, heat is associated with changes of state, such as when a substance transitions from solid to liquid (melting) or from liquid to gas (vaporization). These changes require the absorption or release of heat energy, further illustrating heat's critical role in energy transformation related to temperature differences.

The other options do not capture this concept accurately. Momentum relates to the quantity of motion of a moving body and does not directly involve temperature or state changes. Pressure is a measure of force applied per unit area and does not indicate energy changes due to temperature differences. Potential energy refers to stored energy based on an object's position in a gravitational field or its state, but it also does not involve temperature or changes of state in the same way heat does. Thus, heat is the correct answer as it specifically encompasses the energy aspect related to temperature differences and phase changes.