- amorphous solid: a solid in which particles are not arranged in a regular, repeating pattern that often is formed when molten material cools too quickly to form crystals
- atmosphere: the unit that is often used to report air pressure
- barometer: an instrument that is used to measure atmospheric pressure
- boiling point: the temperature at which a liquid’s vapor pressure is equal to the external or atmospheric pressure
- condensation: the energy-releasing process by which a gas or vapor becomes a liquid
- crystalline solid: a solid whose atoms, ions, or molecules are arranged in an orderly, 3-D structure; can be classified by shape and composition
- Dalton's Law of Partial Pressures: states that the total pressure of a mixture of gases is equal to the sum of the pressures of all the gases in the mixture
- deposition: the energy-releasing process by which a substance changes from a gas or a vapor to a solid without first becoming a liquid
- diffusion: the movement of one material through another from an area of higher concentration to an area of lower concentration
- dipole-dipole forces: the attractions between oppositely charged regions of polar molecules
- dispersion forces: the weak forces resulting from temporary shifts in the density of electrons in electron clouds
- elastic collision: describes a collision in which kinetic energy may be transferred between the colliding particles but the total kinetic energy of the 2 particles remains the same
- evaporation: the process in which vaporization occurs only at the surface of a liquid
- freezing point: the temperature at which a liquid is converted into a crystalline solid
- Graham's Law of Effusion: states that the rate of effusion for a gas is inversely proportional to the square root of its molar mass
- hydrogen bond: a strong dipole-dipole attraction between molecules that contain a hydrogen atom bonded to a small, highly electronegative atom with at least one lone electron pair
- kinetic-molecular theory: explains the properties of gases in terms of the energy, size, and motion of their particles
- melting point: for a crystalline solid, the temperature at which the forces holding a crystal lattice together are broken and it becomes a liquid
- pascal: the SI unit of pressure; one pascal (Pa) is equal to a force of one Newton per square meter
- phase diagram: a graph of pressure versus temperature that shows which phase a substance exists in under different conditions of temperature and pressure
- pressure: force applied per unit of area
- sublimation: the energy-requiring process by which a solid changes directly to a gas without first becoming a liquid
- surface tension: the energy required to increase the surface area of a liquid by a given amount; results from an uneven distribution of attractive forces
- surfactant: a compound, such as soap, that lowers the surface tension of water by disrupting hydrogen bonds between water molecules; also called a surface active agent
- temperature: a measure of the average kinetic energy of the particles in a sample of matter
- triple point: the point on a phase diagram representing the temperature and pressure at which the 3 phases of a substance (solid, liquid, gas) can coexist
- unit cell: the smallest arrangement of connected points that can be repeated in 3 directions to form a crystal lattice
- vapor pressure: the pressure exerted by a vapor over a liquid
- vaporization: the energy-requiring process by which a liquid changes to a gas or vapor
- viscosity: a measure of the resistance of a liquid to flow, which is affected by the size and shape of the particles, and generally increases as the temperature decreases and as intermolecular forces increase