What happens to the temperature of a liquid when it boils?

When a liquid reaches its boiling point, the temperature remains constant despite the continuous input of heat. This phenomenon occurs because the added energy is used to overcome the intermolecular forces holding the liquid molecules together, allowing them to transition into the gaseous state. As a result, while the heat being applied to the system raises the energy level of the liquid, it does not lead to a temperature increase until all of the liquid has turned into vapor.

The boiling point is a critical property of the substance and is influenced by factors such as atmospheric pressure. Once the liquid has fully transitioned to gas, any further addition of heat will increase the temperature of the vapor. This is a fundamental concept in thermodynamics and is essential for understanding refrigeration and HVAC systems, which rely on phase changes to effectively transfer heat.