1. Laws of Attraction Phase Change
Lesson 12.2 and 12.4
Laws of Attraction
Phase Change

2. Intramolecular Forces
Model
Basis
Example
Ionic
Cations and anions
NaCl
Covalent
Shared electrons H2
Metallic
Metal cations and mobile electrons Fe

3. Dispersion Forces Weak Force
Temporary shift in electron density clouds
Explains State of Matter of Halogens
Small to Large
F2 (g)
Cl2 (g)
Br2 (l)
I2 (s)

4. Dipole-dipole Forces
Permanent forces
Positive – Negative Poles

5. Hydrogen Bonds Dipole-dipole attraction
some examples large electronegative
H-F H-O
H-N H-S

6. Room Temperature H2O is liquid NH3 is gas

7. Questions
Explain what determines a substance’s state at a given temperature.
Compare intermolecular and intramolecular forces.
Which molecules can form hydrogen bonds?
a. H2 b. H2S c. HCl d. HF

8. Questions
Explain what determines a substance’s state at a given temperature.
Intermolecular forces – solid very strong, liquid weaker, gas has none
Compare intermolecular and intramolecular forces.
Intramolecular hold particles together, intermolecular between particles
Which molecules can form hydrogen bonds?
a. H2 b. H2S c. HCl d. HF

9. Phase Change

10. Phase Changes that Require Energy
Melting – liquid is warmer than ice, heat is transferred
Vaporization – liquid to vapor or gas gradually
Sublimation – direct from solid to gas

11. Phase Change Release Energy
Freezing – heat is removed
Condensation – what happens to the glass of ice cold lemonade on a hot day?

12. Phase Diagram
Triple
Point

13. Phase Diagram Questions
Explain what the triple point and the critical point on a phase diagram supplies
Determine the phase of water at C and 3.00 atm.

14. Explain what the triple point and the critical point on a phase diagram supplies
Triple point is where all 3 phases can coexist.
Critical point is temp and pressure above which a substance is not a liquid
Determine the phase of water at C and 3.00 atm. liquid

15. Questions
Explain how the addition or removal of energy can cause a phase change.
Explain the difference between the processes of melting and freezing.
Compare disposition and sublimation.

16. Questions
Explain how the addition or removal of energy can cause a phase change.
Add Energy, increase Kinetic Energy, less intermolecular forces
Remove Energy, decrease Kinetic Energy, increase intermolecular forces

17. Explain the difference between the processes of melting and freezing.
Freezing: Liquid to solid, release Energy
Melting: Solid to liquid, need to input Energy
Compare disposition and sublimation.
Sublimation: solid to vapor directly, skips liquid phase
Disposition: Vapor to solid, without liquid phase