<< [[plastic and polymers MOC]], [[Material Properties MOC]] [[Differential scanning calorimetry]] [[glass transition]] Phase transitions can be categorized as ==first or second order==. In all phase transitions, the chemical potential of a system changes continuously with temperature. ## First order phase transitions Derivatives of chemical potential such as [[Enthalpy (H) is the heat energy of a system|enthalpy]], entropy, and volume are ==discontinuous== functions of temperature First order phase transitions are ==transformations between states of matter== ### Examples - Melting - Vaporization - Crystallization ![[Tm.jpg|sm]] ## Second order phase transitions Derivatives of chemical potential such as enthalpy, entropy, and volume are ==continuous== functions of temperature ### Examples - glass transition ![[Tg.jpg|sm]] ## Comparison On a [[Differential scanning calorimetry|DSC thermogram]], a glass transition appears as a baseline shift while crystallization causes a peak. Both transitions create ==a more ordered state==, but crystallization causes a ==sudden increase in entropy== while a glass transition happens more gradually and is accompanied by a ==continuous increase in entropy.== ![[Differential scanning calorimetry#Examples]]