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, geometric, three-dimensional structure; can be classified by shape and by composition
Dalton's law of partial pressure
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 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 two 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 is equal to a force of one newton per square meter
phase diagram
a graph of pressure vs. temperature that shows which phase a substance exists in under different conditions of temperature and pressure
pressure
force applied per unit 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 three phases of a substance (solid, liquid, or gas) can coexist
unit cell
the smallest arrangement of connected points that can be repeated in three 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 particles, and generally increases as the temperature decreases and as intermolar forces increase