Intermolecular Forces and Polarity

Polarity and Intermolecular Forces

Polar vs Nonpolar

• A polar molecule is sharing electrons unequally (two different poles, one positive and the other negative)

• A nonpolar is sharing electrons equally (tug of war with two trucks pulling with the exact same force)

Polar vs Nonpolar

• Polar molecules have a difference in electronegativity that is equal to 0.5 or greater

• Nonpolar molecules have a difference in EN of 0.4 or less

Multiple Choice

Calculate the difference in EN for a H-O bond. Is this bond polar?

• 1.4, Yes

• 1.4, No

• 2.1, Yes

• 2.1, No

INTRAmolecular VS INTERmolecular Forces

INTRAmolecular forces are the bonds that occur inside or within a single moelcule.

INTERmolecular forces (IMF) exist between two or more molecules

Multiple Choice

Intermolecular Forces are the forces that exist

• Between two or more molecules

• Within a single molecule

• Only in molecules containing carbon

• In all molecules

Multiple Choice

Intramolecular forces are the forces that exist

• Between two or more molecules

• Within a single molecule

• Only in compounds containing carbon

• In all molecules

INTRAmolecular Forces

Examples of intramolecular forces include ionic, covalent and metallic bonds.

Multiple Choice

An example of an intramolecular force includes

• ionic

• covalent

• metallic

• all of the above

INTERmolecular Forces

Examples of intermolecular forces include london dispersion (LDF), dipole/dipole, and hydrogen bonding

Multiple Choice

Examples of an intermolecular force include

• london disperson

• dipole dipole

• hydrogen bonding

• all of the above

Intermolecular vs Intramolecular

Ionic and covalent bonds are a much stronger force than intermolecular forces

Multiple Choice

Intramolecular forces are weaker than intermolecular forces

• True

• False

Multiple Choice

Which type of intermolecular force is the strongest?

• LDF

• Dipole Dipole

• Hydrogen Bonding

• Covalent Bonding

Molecule Size/Mass

Larger molecules need stronger forces to hold them together. As the size of the molecule increases so does the strength of the intermolecular force (IMF)

Multiple Choice

As the molecule size increases, the strength of the IMF

• Increases

• Descreases

• Stays the same

Multiple Choice

Which type of force is the weakest?

• LDF

• Dipole Dipole

• Hydrogen Bonding

• Ionic Bonding

London Dispersion Force (LDF)

The weakest force

Occurs between ALL MOLECULES

If a molecule is nonpolar then the only force present will be LDF

Dipole Dipole Forces

• Occurs between all polar molecules

• The attraction of the positive end of one molecule to the negative end of another

Hydrogen Bonding

• Must have a hydrogen directly bonded to a F, N or O.

• Strongest type of intermolecular force

Multiple Choice

For hydrogen bonding to occur, a molecule must have a hydrogen bonded to

• carbon

• another hydrogen

• Fluorine, Chlorine or Oxygen

• Fluorine, Nitrogen or Oxygen

Polar and Nonpolar

• Nonpolar molecules will contain only london dispersion forces

• Polar molecules will contain london dispersion and dipole dipole

• Molecules with hydrogen bonding will contain all three types of forces

Multiple Choice

Which of the following is an example of a polar molecule

• water

• methane

• propane

• carbon dioxide

Viscocity

• How thick a liquid is or how slow it flows

• Viscous liquids have larger moelcules

• Viscous liquids need stronger dispersion forces to hold them molecules close together

Multiple Choice

Which liquid is more viscous (take the longest to pour)

• Honey

• Syrup

• Vegetable Oil

Multiple Choice

Is methane (CH₄) polar or nonpolar?

• Polar

• Nonpolar

Multiple Choice

What forces are present in methane (CH₄)?

• LDF

• Dipole Dipole

• Hydrogen Bonding

• All of the above

Multiple Choice

Which forces are present in H₂O?

• LDF

• Dipole Dipole

• Hydrogen Bonding

• All of the above

Multiple Choice

Does this molecule contain hydrogen bonding?

• Yes

• NO