What are two types of physical or phase changes?

Melting and vaporization are both fundamental phase changes that occur in physical substances. Melting refers to the transition of a solid into a liquid upon the application of heat, which provides the energy needed to overcome the forces holding the particles in a fixed structure. This process occurs at a specific temperature known as the melting point.

Vaporization, on the other hand, is the phase change where a liquid transforms into a gas. This can occur through processes such as boiling, which happens at the boiling point, or evaporation, which occurs at temperatures below the boiling point over a more extended period.

Both processes illustrate the concept of phase changes effectively, as they involve a substance altering its state without a change in chemical composition. Understanding these processes is crucial in fire investigation, where the behavior of materials during heating and the changes they undergo can provide critical clues about the origin and cause of a fire.