What does H = -ml tell us?

The equation H = -ml signifies the relationship between the heat absorbed or released during a phase change, particularly focusing on the condensation process. In this context, "H" represents the heat, "m" stands for the mass of the substance undergoing the phase change, and "l" refers to the latent heat of vaporization or condensation.

When a gas condenses into a liquid, it releases heat into the environment. This process is exothermic; thus, the heat change (H) is negative, indicating that heat is being released when the substance transitions from a gaseous state to a liquid state. The negative sign reflects this release of heat, and the product ml gives the total energy change based on the mass of the substance and the specific latent heat.

This understanding is essential in thermodynamics and describes the behavior of materials during phase transitions, which is critical for applications in various fields, including chemistry and engineering.

The other options do not accurately represent the equation's meaning concerning heat changes in phase transitions.