Phase Changes and Phase Diagrams
Ever wonder why ice melts or water boils? It's all about energy transfer! When substances change from one state to another, they either absorb or release energy. For example, melting occurs when a solid absorbs energy and becomes a liquid, while freezing happens when a liquid releases energy to become a solid.
Water typically freezes/melts at 0°C and boils/condenses at 100°C, but these temperatures depend on air pressure. At higher pressures, water boils at higher temperatures, which is why cooking takes longer at high altitudes where pressure is lower.
A phase diagram shows the temperatures and pressures where different phases of a substance can exist. The lines on these diagrams represent boundaries where phases coexist. The triple point is particularly special—it's the exact temperature and pressure where solid, liquid, and gas phases can all exist simultaneously!
Did you know? Above a certain temperature called the critical temperature (373.99°C for water), the liquid phase cannot exist no matter how much pressure you apply. This is why some substances can never be liquefied at room temperature!
