Chapter 3 Section 2 Changes of State Changes

Chapter 3 Section 2 Changes of State

Changes Between Solid and Liquid • Melting Is the change of state from a solid to a liquid. When a substance melts, the particles in the solid vibrate so fast that they break free from their fixed positions. Melting occurs at a certain temperature called the melting point. • Freezing Is the change of state from liquid to a solid. When a substance freezes, the particles in the liquid move so slowly that they begin to take on fixed positions.

Changes Between Liquid and Gas • Vaporization Is the change from liquid to a gas. Vaporization takes place when the particles in a liquid gain enough energy to move independently, forming a gas. • Evaporation is Vaporization that takes place only on the surface of a liquid. • Boiling Is the change from liquid to gas below its surface as well as at the surface. The temperature at which the liquid starts boiling is called the boiling point. • Condensation Is the change of state from gas to liquid. During condensation, the particles in a gas lose enough thermal energy to form a liquid.

Changes between Solid and Gas • Sublimation occurs when the surface particles of a solid gain enough energy that they form a gas. During sublimation, particles of a solid do not pass through the liquid state as they form a gas.

Summarizing Changes of State Change of state Direction Melting Solid to Liquid Endothermic or Exothermic? endothermic Freezing Liquid to Solid exothermic Vaporization Liquid to Gas endothermic Condensation Gas to Liquid exothermic Sublimation Solid to gas endothermic