CH 12: Intermolecular Forces and Liquids and Solids I.States of Matter a)Kinetic Energy vs. Attractive Forces II.Intermolecular Forces (Attractive, van der Waal Forces) a)Dipole-Dipole--- (Polar Molecules) i.Hydrogen Bonding b)Dispersion (London) Forces--- (NonPolar Molecules) c)Attractive Forces Involving Ions

Intermolecular Forces and Liquids and Solids III.Properties of Liquids a)Viscosity b)Meniscus Formation c)Surface Tension d)Capillary Action IV.Phase Changes a)Equilibrium Vapor Pressure i.Normal boiling point b)Phase Diagrams

Intermolecular Forces and Liquids and Solids V.Crystalline Structure of Solids a)Unit Cells (Simple Cubic, BCC, FCC) i.Coordination Number ii.# Lattice Points in a Unit Cell VI.Radius vs. Unit Cell Edge Length,a a)Density VII.Types of Crystalline Solids a)Ionic, Molecular, Covalent, and Metallic

States of Matter Part I

Three States of Matter 1.5

Factors in Determining State of Matter I.Kinetic Energy II.Intermolecular Forces; Attractive Forces between different molecules neglible in gases important in solids, liquids

GAS-Effect of Kinetic Energy Overwhelms Attractive Force

Liquid – Molecules have Enough Kinetic Energy to Slide Past One Another.

Solid – Molecules Kinetic Energy is NOT Strong Enough to Allow Molecules to Slide Past One Another

Intermolecular Forces (Attractive Forces, van der Waal Forces) Part II

Intermolecular Forces 11.2 er Intermolecular forces; attractive forces between diff. Molecules which bring the molecules in contac with eac other ra Intramolecular forces hold atoms together in a molecule. Intermolecular vs Intramolecular 41 kJ to vaporize 1 mole of water (inter) 930 kJ to break all O-H bonds in 1 mole of water (intra) Generally, intermolecular forces are much weaker than intramolecular forces. “Measure” of intermolecular force boiling point melting point  H vap  H fus  H sub

Types of Intermolecular Forces 1.Dipole/ Dipole Forces (Polar Molecules) Hydrogen Bonds 2.London/ Dispersion Forces (NonPolar Molecules)

Intermolecular Forces I. Dipole-Dipole Forces Attractive forces between polar molecules Orientation of Polar Molecules in a Solid 11.2

Intermolecular Forces II. Dispersion Forces Attractive forces that arise as a result of temporary dipoles induced in atoms or nonpolar molecules 11.2

Polarizability Ease at which the electron distribution in an atom or molecule can be distorted and a temporary dipole induced –More electrons (greater Molar Mass) leads to greater polarizability.

Formation of Temporary Dipoles 1. Random movement of electrons 2. ion-induced dipole interaction 3. dipole-induced dipole interaction

S O O What type(s) of intermolecular forces exist between each of the following molecules? HBr HBr is a polar molecule: dipole-dipole forces. There are also dispersion forces between HBr molecules. CH 4 CH 4 is nonpolar: dispersion forces. SO 2 SO 2 is a polar molecule: dipole-dipole forces. There are also dispersion forces between SO 2 molecules. 11.2

Boiling Point- Temperature at which there is enough Kinetic Energy to Overcome Intermolecular Forces Liquid Has Intermolecular Forces Gas No Intermolecular Forces

Boiling Point Increases with.. 1.Stronger Intermolecular Force 2.If same Intermolecular Force; increasing Molar Mass, higher boiling point

Explain why the Higher Molar Mass Compound, CF 4, has a Lower Boiling Point than H 2 Se CF 4 Boiling Point; °C Molar Mass ~ 88 g/mole H 2 Se Boiling Point; °C Molar Mass ~ 81 g/mole Intermolecular Force; Dispersion Force Intermolecular Force; Dipole-Dipole Force

Boiling Points of Polar Hydrogen Compounds Approximate Molar Mass; g/mole Boiling Point; °C H2OH2O H2SH2S34-60 H 2 Se81-42 H 2 Te130-2

Hydrogen Bond Strong Type of Dipole-Dipole Force. This Type of Intermolecular Force Happens When H is directly bonded to O, N, or F.

High Strength of H- bond 1.Large electronegativity difference between H and N, O, or F. 2.Small size of H atom allows it to get close to another molecule

Hydrogen Bond O-H Covalent Bond that Makes H-bonding Possible

Which of the Two Polar Molecules Has a Higher Boiling Point ?

Importance of H-Bonds in H 2 O 1.Very high boiling point for water (H 2 O(l)) for its Molar Mass. 2.The solid form of the material is less dense than liquid form Ice Floats on liquid water. Water expands as it freezes

Ice Cubes float on water (Left) Solid benzene sinks to the bottom of liquid benzene (right)

Importance of H-Bonds in H 2 O 1.Very high boiling point for water (H 2 O(l)) for its Molar Mass. 2.Ice floats on liquid water. The solid form of the material is less dense than liquid form Water expands as it freezes 3.High specific heat of Water

Determining Type of Intermolecular Force Polar Molecules ? Dispersion/ London Forces H Directly Bonded to O, N, or F ? Dipole/Dipole Force Hydrogen Bonding Increasing Strength of Intermolecular Force NO YES NOYES