| A | B |
|---|
| allotrope | one of two or more different molecular forms of an element in the same physical state |
| amorphous solid | a term used to describe a solid that lacks an ordered internal structure; denotes a random arrangement of atoms |
| atmospheric pressure | the pressure exerted by air molecules in the atmosphere surrounding Earth, resulting from collisions of air molecules with objects |
| barometer | an instrument used to measure atmospheric pressure |
| boiling point | the temperature at which the vapor pressure of a liquid is just equal to the external pressure on the liquid |
| crystal | a substance in which the atoms, ions, or molecules are arranged in an orderly, repeating, three-dimensional pattern called a crystal lattice |
| evaporation | vaporization that occurs at the surface of a liquid that is not boiling |
| gas pressure | the force exerted by a gas per unit surface area of an object; due to collisions of gas particles with the object |
| glass | the optically transparent fusion product of inorganic materials that have cooled to a rigid state without crystallizing |
| kinetic energy | the energy an object has because of its motion |
| kinetic theory | a theory explaining the states of matter, based on the concept that the particles in all forms of matter are in constant motion |
| melting point | the temperature at which a substance changes from solid to a liquid |
| normal boiling point | the boiling point of a liquid at a pressure of 1 atmosphere |
| pascal (Pa) | the SI unit of pressure |
| phase diagram | a diagram showing the conditions at which a substance exists as a solid, liquid, or vapor |
| standard atmosphere (atm) | a unit of pressure; it is the pressure required to support 760 mm of mercury in a mercury barometer at 25 degrees C; this is the average atmospheric pressure at sea level |
| sublimation | the conversion of a solid to a gas or vapor without passing through the liquid state |
| triple point | the point on a phase diagram that represents the only set of conditons at which all three phases exist in equilibrium with one another |
| unit cell | the smallest group of particles within a crystal that retains the geometric shape of the crystal |
| vacuum | a space where no particles of matter exist |
| vaporization | the conversion of a liquid to a gas or a vapor |
| vapor pressure | the pressure produced when vapor particles above a liquid in a sealed container collide with the container walls; a dynamic equilibrium exists between the vapor and the liquid |
