2. Catalyst 1. List the substance in order of increasing intermolecular forces: BaCl 2, H 2, CO, HF, and Ne. 2. Order the molecules in order of increasing intermolecular forces CH 3 CH 3, CH 3 OH, CH 3 CH 2 OH End

4. Lecture 4.6 – Phase Changes and Diagrams

5. Today’s Learning Targets LT 4.9 – I can interpret a phase diagram for a substance and identify areas of solid, liquid, gas, phase changes, triple point and critical point.

6. Phase Changes A substance changes phases due to changes in either temperature or pressure. Solid  Liquid = Melting Liquid  Solid = Freezing Liquid  Gas = Vaporization Gas  Liquid = Condensation Solid  Gas = Sublimation Gas  Solid = Deposition

7. Vapor Pressure and Boiling Point A liquid boils when the vapor pressure is equal to the pressure above the liquid When this point is achieved, vapor bubbles form within the liquid and boiling is observed Boiling point of a substance increases with the pressure of the environment.

8. Phase Diagrams The phase that a substance is is dependent upon both the pressure and temperature of the surrounding environment A phase diagram shows the relationship between temperature, pressure, and phase of a substance.

10. Important Points on Phase Diagrams The triple point is the pressure and temperature where all three phases are present. The critical point is the pressure and temperature at which beyond that point gas and liquid exist as a supercritical fluid Kinetic energy is far to great for a purely liquid state to exist, but attractive forces are far to great for a purely gas state to exist

11. Liquid/Solid Phase Line Almost all substances have a solid/liquid line that bends to the right. Water is the only substance that has a solid/liquid line that bends to the left Water bends to the left because it is one of the few substances whose liquid is more dense than its solid

12. Class Example Imagine a substance with the following points on the phase diagrams: a triple point at.5 atm and -5 oC, a normal melting point at 20 oC, a normal boiling point at 150 oC, and a critical point at 5 atm 1000 oC. The solid phase is more dense then the liquid phase. Draw this phase diagram.

13. Table Talk A substance has a triple point of -56.4 o C and 5.1 atm, a normal sublimation point at -78.5 o C, and a critical point of 31 o C and 73.0 atm.

14. With your group complete the following phase diagram problems Assign roles as follows: 1 = Identify what is given 2 = Explain how to set up problem/graph 3 = Solve the problem Rotate roles after each problem Collaborative Poster

16. Closing Time Read 11.4 (skip pages 439 to middle of 441) and 11.6 FRQ Practice Problems Due Thursday