What is the process called when heat is transferred without any change in the temperature of a substance?

The process where heat is transferred without a change in temperature is referred to as latent heat. This concept is pivotal in thermodynamics and plays a significant role in phase changes of substances. When a substance undergoes a phase change—such as melting, boiling, or sublimation—the heat energy being added or removed does not affect the temperature of the substance; rather, it is used to change the state of the substance.

For example, during the melting of ice, the temperature remains constant at 0 degrees Celsius until all the ice has melted into water. Similarly, during the boiling of water, the temperature remains at 100 degrees Celsius until all the water has transitioned into steam. This constant temperature during a phase change occurs because all the heat energy is being utilized in breaking the intermolecular forces that hold the particles in their current state, rather than increasing their kinetic energy, which would raise temperature.

Understanding latent heat is crucial in fields like HVAC, meteorology, and other engineering disciplines, as it influences energy transfer processes significantly.