What does heat measure?

Heat measures the transfer of thermal energy between systems or within a system due to a temperature difference. It is not a measure of energy stored within an object, but rather how energy moves from one place to another. When two objects at different temperatures come into contact, thermal energy will flow from the hotter object to the cooler one until thermal equilibrium is reached. This process, characterized by the movement of energy, is what heat quantifies.

The other options refer to different concepts in thermodynamics. The total energy in a system encompasses all forms of energy, including potential and kinetic energy, but it does not specifically address the transfer aspect. The internal energy of a stationary object typically refers to the total energy contained within that object, including all forms of energy, but does not specifically pertain to heat transfer. Kinetic energy of particles relates to the energy of their motion and is a component of internal energy. While related, these concepts do not define heat as the measurement of thermal energy transfer.