Monday november 25th

Intermolecular forcesAim: What are the forces that hold molecules together?

Extra Credit Project

Due Monday 12/2

Homework: IMF practice

worksheet

Unit 3b ExamWednesday 12/4

DO NOW WILL BE COLLECTED AT THE END OF THE TIMER← ← ← ← ←

★ Inter vs. Intra● Using the image on the right,

describe the difference between intermolecular and intramolecular forces:

Intramolecular forces are IN

a molecule, while

intermolecular forces are

BETWEEN molecules.

● Intermolecular forces (IMF): Weak forces of attraction BETWEEN molecules

★ London Dispersion Forces (aka Van der Waals forces)

● Weakest IMF

● Occurs between Nonpolar molecules

● Explains how nonpolar molecules can exist in solid and liquid phases.

● The more electrons, the stronger the London dispersion forces. (Example: Bromine has more electrons than chlorine, bromine will have stronger dispersion forces)

★ Dipole-Dipole Attraction ● Second strongest intermolecular

attraction

● Between polar covalent molecules

● The partial negative end of the dipole is attracted to the partial positive end of another dipole

● Greater polarity = Stronger IMF

★ Hydrogen Bonding ● Strongest IMF (note: H-bonding is

an IMF… not a form of bonding!!)

● Extreme Dipole (super polar bond) due to most electronegative elements

● Occurs between a hydrogen of one molecule and F, O or N in another (The hydrogen needs to be attached to a F, O, or N)● Memory trick: “H bonding is

FON”

★ Effects of IMF on Physical Properties ● They are what make solid and

liquid molecular compounds possible.

o The stronger the attractions, the closer the molecules.

● They attribute to the temperature at which a substance boils/melts

o The stronger the attraction, the higher the melting and boiling points.

★ Check for understanding The molar masses and boiling points at standard pressure for four compounds are given in the table.

Which compound has the strongest intermolecular forces?a. HF b. HC c. HBr d. HI

Reasoning: HF has the strongest intermolecular forces because there is hydrogen bonding between the molecules. (Note: You can tell HF has the strongest intermolecular forces because it has the highest boiling point.)

★ Check for understanding The molar masses and boiling points at standard pressure for four compounds are given in the table.

Which compound has the strongest intermolecular forces?a. HF b. HC c. HBr d. HI

Reasoning: HF has the strongest intermolecular forces because there is hydrogen bonding between the molecules. (Note: You can tell HF has the strongest intermolecular forces because it has the highest boiling point.)

Regents alert!!

HYDROGEN BONDING

IN H2O

● Hydrogen bonding is the strongest intermolecular force

● Hydrogen bonding occurs between molecules of water

● Hydrogen bonding in water explains water’s high boiling point

(100% guaranteed to be on the regents)

Relative Strength of Intermolecular Forces of AttractionIntermolecular Force Occurs Between… Relative Strength

Dispersion forces Nonpolar molecules 3rd (weakest)

Dipole-dipole forces polar covalent molecules 2nd

Hydrogen bonding

molecules in which hydrogen is bound to a highly

electronegative atom, such as nitrogen, oxygen, or fluorine.

1st (strongest)

Type of Compound Intermolecular forces present

Relative order of boiling and melting points

Ionic compoundsstrong electrostatic forces

that exist between oppositely charged ions

1 (highest MP & BP)

Covalent compounds containing hydrogen bonds

Hydrogen bonds 2

Polar covalent compounds Dipole-dipole forces 3

Nonpolar covalent compounds

Dispersion forces 4 (lowest MP & BP)

★ Network Solids

● A network solid or covalent network solid is a chemical compound (or element) in which the atoms are bonded by covalent bonds in a continuous network extending throughout the material.

● In a network solid there are no individual molecules (much like an ionic crystal)

● The atoms of network solids can bond to one another in chains, rings, and networks.

● Carbon can form network solids. Ex: diamond, graphite , carbon nanotubes, buckyball (C60)

Tuesday november 26th

Chemical bonding cer

Extra Credit Project

Due Monday 12/2

Unit 3b ExamWednesday 12/4

Peer review the do now