1.7 Intermolecular Forces

H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl Pour liquid between 2 beakers along with this slide. Is this evaporating? What does evaporating look like, in terms of these molecules? Is this evaporating very fast? Why? H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl

H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl d+ d- H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl

d+ d- H Cl H Cl H H Cl Cl H Cl H Cl H Cl H H Cl

d+ d- H Cl

d+ d- H Cl

Intermolecular Forces Attraction forces between molecules

Intramolecular Force Intermolecular Force Ionic bond Covalent bond Polar covalent bond Hold together ATOMS Breaking = chemical reaction Dipole-dipole London forces Hydrogen bond Hold together MOLECULES Breaking = phase change, dissolving

Practice: Which of the following molecules are polar?   CH4 H2O NH3 

C. Hydrogen Bonds molecule contains an H atom bonded to a very electronegative atom (_____, _____, ____) the H atom of one molecule is attracted to the F, O, or N on another molecule F O N

C. Hydrogen Bonds molecule contains an H atom bonded to a very electronegative atom (_____, _____, ____) the H atom of one molecule is attracted to the F, O, or N on another molecule the strongest of the intermolecular forces H has no e- to get in the way of its attraction to F, O, or N F O N

H – F H – F What would be something that would get in the way of intermolecular forces?

H – F H – F

Example: Which of the following molecules can hydrogen bond? HCN H2O H2S HF

Arrange water molecules to reflect the structure of ice.

Example: Which would you expect to have a higher melting point, CCl4 or CHCl3?