Practice: AP Chemistry intermolecular forces

Definition of intermolecular forces

Forces that occur between molecules, affecting physical properties like boiling and melting points.

Types of intermolecular forces

1. Hydrogen bonding 2. Dipole-dipole interactions 3. London dispersion forces

True or false: Hydrogen bonds are the strongest intermolecular force

True, because they occur between hydrogen and highly electronegative atoms like O, N, or F.

Difference between dipole-dipole and London dispersion forces

Dipole-dipole forces occur between polar molecules; London dispersion forces can occur in all molecules due to temporary dipoles.

Factors affecting London dispersion forces

1. Molecular size 2. Shape of the molecule 3. Surface area

Fill in the blank: Hydrogen bonding requires a hydrogen atom bonded to _______

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

What is a polar molecule?

A molecule that has a net dipole moment due to its geometry and polar bonds.

Question: What primarily determines boiling points?

The strength of intermolecular forces; stronger forces lead to higher boiling points.

Characteristics of ionic compounds

High melting/boiling points due to strong electrostatic forces between ions.

True or false: All molecules exhibit London dispersion forces

True, because all molecules can form temporary dipoles.

Question: What enhances hydrogen bonding?

The presence of highly electronegative atoms like O, N, or F.

Comparison: Ionic vs. covalent compounds

Ionic compounds are formed by transfer of electrons; covalent compounds share electrons.

Question: What is viscosity?

A measure of a fluid's resistance to flow, influenced by intermolecular forces.

What is surface tension?

The energy required to increase the surface area of a liquid, related to intermolecular forces.

True or false: Higher temperature decreases viscosity

True, because increased kinetic energy allows molecules to move more freely.

Factors that increase hydrogen bonding

1. Availability of hydrogen atom 2. Presence of electronegative atoms.

Question: Which type of intermolecular force is strongest?

Hydrogen bonding is typically stronger than dipole-dipole and London dispersion forces.

Comparison: Strong vs. weak intermolecular forces

Strong forces result in higher boiling/melting points compared to weak forces.

What is a nonpolar molecule?

A molecule that does not have a net dipole moment; electrons are evenly distributed.