pressure
force exerted per unit area of surface
acceleration
change of speed per unit time
pascal (Pa)
SI unit of pressure; 1 Pa = 1kg/(m x s^2)
barometer
device for measuring the pressure of the atmosphere
manometer
device that measures the pressure of a gas or liquid in a sealed vessel
millimeters of mercury (mmHg or torr)
traditional unit of pressure equal to that exerted by 1-mm column of mercury at 0.00 degrees C in a barometer or manometer
atmosphere (atm)
traditional unit of pressure equal to exactly 760 mmHg;1 atm = 101.325 kPa exact
bar
unit of pressure equal to 1 x 10^5 Pa, slight less than 1 atm
compressibility
ability to be squeezed into a smaller volume by the application of pressure
Boyle's law
the volume of a sample of gas at a given temperature varies inversely with the applied pressure
linearly
term describing how one variable changes with the change in another variable if a plot of the two variables gives a straight line
extrapolate
to extend a line beyond the plotted data points
Kelvin scale
absolute temperature scale on which the units (kelvins, K) are given by K= degrees C+ 273.15
Charles's law
the volume occupied by any sample of gas at a constant pressure is directly proportional to the absolute temperature
law of combining volumes
the volumes of reactant gases at a given pressure and temperature are the ratios of small whole numbers
Avogadro's law
equal volumes of any two gases at the same temperature and pressure contain the same number of molecules
molar gas volume (Vm)
volume occupied by one mole of any gas at a given temperature and pressure
standard temperature and pressure (STP)
reference conditions for gases chosen by convention to be 0 degrees C and 1 atm pressure
molar gas constant (R)
constant of proportionality relating the molar volume of a gas to T/P
ideal gas law
mathematical expression combining all the gas laws and relating the volume (V), pressure (P), Kelvin temperature (T), and the moles (n) of a gas to the molar constant R; PV=nRT
Amonton's law
the pressure of a given amount of gas at a fixed volume is proportional to the absolute temperature
partial pressure
pressure exerted by a particular gas in a gas mixture
Dalton's law of partial pressures
the sum of the partial pressures of all the different gases in a mixture is equal to the total pressure of the mixture
mole fraction
fraction of moles of a component gas in the total moles of a gas mixture
vapor pressure
partial pressure of the molecules of a substance in the gaseous state in the presence of the liquid )(or solid) substance
kinetic-molecular theory of gases (kinetic theory)
idea that a gas consists of molecules in constant random motion
postulates
basic statements from which all conclusions or predictions of a theory are deduced
ideal gas
gas that follows the ideal gas law; its molecules have essentially no volume of their own and no attraction for each other
intermolecular forces
forces of attraction or repulsion between molecules
root-mean-square (rms) molecular speed (u)
type of average molecular speed, or the speed of a molecule that has the average molecular kinetic energy; can be shown equal to u = (3RT/Mm)^1/2 where R is the molar gas constant,T is kelvin temperature, and Mm is the molar mass for the gas
diffusion
process whereby a gas spreads out through another gas to occupy the space uniformly
effusion
escape of a gas through a small hole into a vacuum at the same velocity it had in the container
Graham's law of effusion
the rate of effusion of gas molecules from a particular hole is inversely proportional to the square root of the molecular mass of the gas at constant T and P
enrichment
process used to increase the percentage of one isotope in a sample
van der Waals equation
equation similar to the ideal gas law, but it includes two constants, a and b, to account for deviations from ideal behavior