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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
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