States of Matter, Phase Changes & Intermolecular Forces – Chapter 7 Review

Question-and-answer flashcards reviewing phase changes, heat flow, evaporation, vapor pressure, volatility, and the three primary intermolecular forces (hydrogen bonding, dipole-dipole, and London dispersion).

What phase change converts a liquid to a solid?

Freezing.

Which phase change converts a liquid to a gas?

Evaporation (or vaporization).

During condensation, matter changes from which state to which state?

From gas to liquid.

What is the direct transition from solid to gas called?

Sublimation.

Melting represents a change from to .

Solid to liquid.

What is the reverse of sublimation, where a gas turns directly into a solid?

Deposition.

When heat is added to a system, is the process endothermic or exothermic?

Endothermic.

Removing heat from a system corresponds to what type of thermal process?

Exothermic.

How do surface area and temperature each affect the rate of evaporation of a liquid?

Both increased surface area and higher temperature increase the evaporation rate.

Define a vapor in terms of temperature, pressure, and usual phase expectation.

A vapor is a gas that exists at a temperature and pressure where the substance is ordinarily expected to be a solid or liquid.

What condition exists when the rate of a forward process equals the rate of its reverse process?

Dynamic equilibrium.

What is vapor pressure?

The pressure exerted by a vapor above its liquid when the two are in equilibrium.

How do strong intermolecular attractions affect vapor pressure?

Stronger attractions lower the vapor pressure.

Substances that evaporate readily at room temperature are described as _.

Volatile.

List the three main types of intermolecular forces in order of decreasing strength.

Hydrogen bonding > Dipole–dipole interactions > London (dispersion) forces.

Which atoms must hydrogen bond directly to H for hydrogen bonding to occur?

Fluorine (F), Oxygen (O), or Nitrogen (N).

Between two compounds that both exhibit hydrogen bonding, what property often determines which has stronger overall intermolecular forces?

Higher molar mass typically corresponds to stronger hydrogen-bonding interactions.

Why do London dispersion forces become stronger as molar mass increases?

More electrons and a larger electron cloud make momentary dipoles larger, increasing the dispersion force.

What type of molecules experience dipole-dipole interactions?

Polar molecules.

How does molecular polarity influence the strength of dipole-dipole forces?

Greater polarity leads to stronger dipole-dipole interactions.