Intermolecular Forces and Phase Changes: Key Concepts in Chemistry

What are the three states of matter?

Solid, liquid, and gas.

What are intermolecular forces (IMF)?

Attractive and repulsive forces experienced between molecules and/or atoms.

How do intermolecular forces compare to intramolecular forces?

IMF are weaker than intramolecular forces, which are bonds within molecules.

What are the physical properties affected by intermolecular forces?

Melting point, boiling point, vapor pressure, viscosity, surface tension, and density.

What are London dispersion forces?

Weak intermolecular forces arising from temporary dipoles in molecules.

What are dipole-dipole interactions?

Attractive forces between the positive end of one polar molecule and the negative end of another.

What is hydrogen bonding?

A strong type of dipole-dipole interaction that occurs when hydrogen is bonded to highly electronegative atoms like N, O, or F.

What is an ion-dipole interaction?

An attractive force between an ion and a polar molecule.

What is polarization in the context of intermolecular forces?

Charge separation within an atom or molecule, which can lead to induced dipoles.

What is an induced dipole?

A temporary dipole that occurs when a nonpolar molecule is in close proximity to a polar molecule.

How does molecule size affect London dispersion forces?

Larger molecules have more surface area for interaction and a larger electron cloud, making them easier to polarize.

What is the significance of molecule shape in intermolecular forces?

Molecules with identical formulas but different shapes can experience different London forces.

What is viscosity?

A measure of a liquid's resistance to flow, which increases as intermolecular forces increase.

What is surface tension?

The tendency of liquid molecules at the surface to stick together due to stronger intermolecular attractions.

What is vapor pressure?

The force exerted by gas molecules over an area of a container, dependent on temperature.

What is the boiling point?

The temperature at which vapor pressure equals atmospheric pressure.

What does a phase diagram illustrate?

The relationships between phases of a substance at various pressure-temperature combinations.

What is the Triple Point in a phase diagram?

A unique pressure-temperature combination at which a substance exists in all three phases: solid, liquid, and gas.

What happens to ice when pressure is applied?

Ice melts when pressurized, which is a unique property of water.

What is the effect of adding heat to a material?

It increases the vibrational motion of atoms, molecules, and ions, and can overcome intermolecular forces.

What is the relationship between melting point and intermolecular forces?

Melting point increases as intermolecular forces increase.

What is the relationship between boiling point and intermolecular forces?

Boiling point increases as intermolecular forces increase.

How does temperature affect vapor pressure?

As temperature increases, kinetic energy increases, leading to higher vapor pressure.

What is the significance of the critical point in a phase diagram?

Beyond the critical point, gas and liquid phases of a substance become indistinguishable.

What is the effect of molecular weight on intermolecular forces in nonpolar molecules?

IMF decrease as molecular weight decreases.

How do intermolecular forces affect the boiling point of acetic acid and 1-propanol?

Their boiling points differ due to the different number of hydrogen bonds.

What is the relationship between molecular polarity and intermolecular forces?

Dipole interactions are generally more important when there is a small size difference between molecules.