Chemistry 2 Midterm: Intermolecular Forces of Attraction Review

Phase Changes and Properties

• The temperature at which water freezes to become ice or ice melts to become water is the same.
• Critical temperature and pressure of water are 374°C and 218 atm, respectively.
• Liquid CO2 exists at temperatures above 31.1°C, and its critical point is 31.1°C at 73 atm.

Solutions

• A solution typically consists of a single solvent and one or more solutes.
• The solvent is the substance in greater amounts or the one that dissolves other substances.
• Solutes are the substances in lesser amounts that are dissolved by the solvent.
• The solubility of gaseous solutes in water decreases as temperature increases.

Boiling Point

• The boiling point is the temperature at which the vapor pressure of a liquid is equal to the atmospheric pressure.
• There is an inverse relationship between vapor pressure and boiling point: higher vapor pressure leads to a lower boiling point, and vice versa.

Examples of Liquid Properties

• Rubbing alcohol feels cold when applied to the skin due to evaporative cooling, as it quickly evaporates and absorbs heat from the skin.
• The temperature of a boiling liquid remains constant when heat is continuously added because the added heat is used to convert the liquid into vapor.

Phase Diagram

• A phase diagram is a graphical representation of the pressure-temperature relationship that applies to the equilibria between the phases of substances.
• The triple point is the point where all states of matter exist at the same time.
• The critical point is the temperature at which a gas can no longer be liquefied.
• The temperature of an ice-water mixture, commonly known as the freezing point of water, is 0°C (32°F) under standard atmospheric pressure.

Intermolecular Forces of Attraction

• London dispersion forces are the weakest type of intermolecular force, occurring between nonpolar molecules, and are present in all types of molecules.
• Dipole-dipole forces occur between polar molecules, forming permanent dipoles.
• Hydrogen bonding is the strongest type of intermolecular force, a special type of dipole-dipole force, occurring between H and F, O, or N.

Properties of Liquids

• Surface tension is the force that causes the molecules in the liquid to tighten their hold on one another, directly related to the intermolecular forces of attraction.
• Viscosity is the measure of a liquid's tendency to resist flowing motion, directly influenced by the strength of intermolecular forces.
• Vapor pressure is a characteristic of the type of liquid, dependent on the temperature of the liquid, and occurs when a liquid vaporizes in a closed container.