Chapter 13 Notes Sub day Pre Ap students- copy down these notes for Chapter 13. There are two diagrams included. I encourage you to copy these down, as well. I will explain them, in greater detail, when I return. BE GOOD!!!

Phase Changes Phases physically distinct parts of a mixture that coexist Ex. ice and water - Phase Changes – add or remove energy  Endothermic Phase Changes (addition)‏ - Heat is the transfer of energy from an object at higher T to one at lower T - The T at which the forces holding the particles in a solid together are broken is called the melting point

- During a phase change the T of a substance remains constant - Vaporization – liquid changes to gas or vapor - If energy change is gradual, vaporization takes place with the molecules on the surface – called evaporation - When evaporation takes place, vapor collects at the surface of the liquid and then exerts a pressure on the surface - vapor pressure

- T at which the vapor pressure (VP) of liquid equals the atmospheric pressure is called the boiling point - Sublimation – change directly from solid to gas Ex. Dry ice or ice in the freezer  Exothermic Phase Changes (removal)‏ - Condensation – gas (or vapor) becomes liquid - Deposition – change directly from gas (vapor) to solid Ex. Formation of frost, hail in clouds

- Freezing point – T at which a liquid is converted into solid (solidification)‏  Phase Diagrams – graph that shows in which phase a substance exists under different conditions (pressure and T)‏ - Triple point – point on a phase diagram that represents the T and P at which the 3 phases coexist - Critical temperature- Critical temperature-DEF- is the temperature above which the substance cannot exist in the liquid state. - Critical pressure- DEF- the lowest pressure at which the substance can exist as a liquid at the critical temperature. - Critical point – indicates the critical T and P above which a substance cannot exist as a liquid