InterMolecular Forces (IMF)

Today’s Objectives

◻ Identify and describe the intermolecular forces present in molecules.

◻ Rank molecules based on the intermolecular forces involved.

◻ Assess your knowledge of chemical bonding

Bond Properties

Four Types of Bonds1.

2.

3.

4.

Bond Properties: RECALL

Type of Bond Conduct

ElectricityDissolve State at

Room Temp

POLAR N Y Liquid

IONIC Y(aqueous solutions

and when melted)

Y Solid

NON-POLAR N N Gas

METALLIC Y N Solid

MEMORIZE THIS !!

Warm Up -- Shoulder Buddy Pair

◻ Complete the following chart

Compound Type of Molecule

(I, M, PC, NPC)

Conduct

Electricity?

Dissolve in

Water?

State of Matter

@ Room

Temp?

HCl

Cl-Cl

PH3

BaS

CCl2Br2

Warm Up -- Ck it

◻ Complete the following chartCompound Type of Molecule

(I, M, PC, NPC)

Conduct

Electricity?

Dissolve in

Water?

State of Matter

@ Room

Temp?

HCl PC N Y Liquid

Cl-Cl NPC N N Gas

PH3Polar Covalent No Yes Liquid

BaS Ionic Yes Yes Solid

CCl2Br2 Polar Covalent No Yes Liquid

Watch video on InterMolecularForces ( IMFs)

1. Identify and describe the intermolecular forces present in molecules.

2. Identify and describe the intermolecular forces present in molecules.

3. Rank molecules based on the intermolecular forces involved.

Objectives

May the Forces be with You

◻ Intramolecular forces- forces within a molecule (bonds!)

◻ Intermolecular forces- the attractions between COVALENT molecules that account for properties such as BP, MP, viscosity, surface tension, and solubility.

◻ Copy in notes

Types of Intermolecular Forces

◻ Three types: ⬜ London Dispersion Forces - WEAKEST

⬜ Dipole-Dipole

⬜ Hydrogen bonding - STRONGEST

London Dispersion

◻ Also called induced dipole

◻ Between non-polar covalent molecules

◻ Very very weak

https://www.youtube.com/watch?v=ikKiQIYnqXA

Dipole-Dipole

◻ Between polar molecules AKA dipoles

◻ Two oppositely charged ends.(one + and one -)

◻ They act like little magnets

Hydrogen Bonding

◻ The king of intermolecular forces.

◻ Polar molecules with Hydrogen bonded to Nitrogen or Oxygen or Fluorine

◻ Extremely strong.

◻ Accounts for the very special properties of water

◻ https://www.youtube.com/watch?v=UukRgqzk-KE

◻ https://www.youtube.com/watch?v=dBBEpPFNCEs&index=10&list=PLUZuOzXtHwnBAa9pMPc_mOXX8IWC2grR2

Hydrogen Bonding in Water

Hydrogen bonding in water is responsible for the following properties :• Ice floats• Surface tension• Cohesion• Capillary action

Ranking Intermolecular Forces

◻ The stronger the IMF the higher the Boiling point and Melting point.

Hydrogen Bonds

Dipole-Dipole

London Dispersion

IncreasingBP/MP

Learning Team Activity

Team Discussion

◻ Identify the IMF in each of the following then rank from lowest to highest boiling point

Compound

Lewis Dot

Shape Polar/

Nonpolar

IMF RANK 1-4

1=LOW BP

PH3

CH2Cl2

CO2

H2O

Practice

◻ Now…rank them in order of increasing boiling point.

CO2

H2O

CH2Cl2

PH3

INCREAS ING

Practice

Now…rank them in order of increasing boiling point.

CO2 Linear / Nonpolar / London Disp

CH2Cl2 Tetrahedral / Polar /Dipole-dipole

PH3 Trigonal Pyramidal/Polar/Dipole-Dipole

H2O Bent / Polar / Hydrogen Bonding

INCREAS ING

Turn & Talk

◻ Which will have a higher melting point? Why?

⬜ NH3 or PH3

◻ Which will have a higher melting point? Why?

⬜ NH3 or PH3

NH3 will have a higher melting point because it contains Hydrogen Bonding between the H of one molecule and the N of another molecule. (See picture below)

PH3 has dipole-dipole forces.

You Try #1 (INDEPENDENT WORK)

Compound Shape Polar/Nonpolar IMF

H2

NH3

CO

Identify the IMF in each of the following THEN rank them for increasing boiling point

Put away supplies andReturn to Your Desk.

You Try

◻ Rank the following in order of increasing boiling point.

H2 CO NH3

You Try

◻ Rank the following in order of increasing boiling point.

H2 CO NH3

◻ H2 does NOT have H-bonding, only London and has only single bonds within the atom

◻ CO has dipole-dipole making BP higher than H2

◻ NH3 has Hydrogen, thus highest BP

Homework

Unit 4 Test is FRIDAY 10.12.18

You Will Create & Complete the IMF column Tonight I

MF