| 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 |
| vaporization | the energy-requiring process by which a liquid changes to a gas or vapor |
| vapor pressure | the pressure exerted by a vapor over a liquid |
| 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 |