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

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

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)

Dipole-dipole Forces Permanent forces Positive – Negative Poles

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

Room Temperature H2O is liquid NH3 is gas

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

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

Phase Change

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

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

Phase Diagram Triple Point

Phase Diagram Questions Explain what the triple point and the critical point on a phase diagram supplies Determine the phase of water at 75.00 C and 3.00 atm.

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 75.00 C and 3.00 atm. liquid

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.

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

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