Glossary

absolute zero

the lowest possible temperature; the temperature at which all molecular motion ceases

Avogadro’s number

$N_{\text{A}}$ , the number of molecules or atoms in one mole of a substance; $N_{\text{A}}=6\text{.}\text{02}\times {\text{10}}^{\text{23}}$ particles/mole

Boltzmann constant

$k$ , a physical constant that relates energy to temperature; $k=\text{1.38}\times {\text{10}}^{\text{–23}}\text{J/K}$

Celsius scale

temperature scale in which the freezing point of water is $0\text{º}\text{C}$ and the boiling point of water is $\text{100}\text{º}\text{C}$

coefficient of linear expansion

$\alpha$, the change in length, per unit length, per $1\text{º}\text{C}$ change in temperature; a constant used in the calculation of linear expansion; the coefficient of linear expansion depends on the material and to some degree on the temperature of the material

coefficient of volume expansion

$\beta$, the change in volume, per unit volume, per $1\text{º}\text{C}$ change in temperature

critical point

the temperature above which a liquid cannot exist

critical pressure

the minimum pressure needed for a liquid to exist at the critical temperature

critical temperature

the temperature above which a liquid cannot exist

Dalton’s law of partial pressures

the physical law that states that the total pressure of a gas is the sum of partial pressures of the component gases

degree Celsius

unit on the Celsius temperature scale

degree Fahrenheit

unit on the Fahrenheit temperature scale

dew point

the temperature at which relative humidity is 100%; the temperature at which water starts to condense out of the air

Fahrenheit scale

temperature scale in which the freezing point of water is $\text{32}\text{º}\text{F}$ and the boiling point of water is $\text{212}\text{º}\text{F}$

ideal gas law

the physical law that relates the pressure and volume of a gas to the number of gas molecules or number of moles of gas and the temperature of the gas

Kelvin scale

temperature scale in which 0 K is the lowest possible temperature, representing absolute zero

mole

the quantity of a substance whose mass (in grams) is equal to its molecular mass

partial pressure

the pressure a gas would create if it occupied the total volume of space available

percent relative humidity

the ratio of vapor density to saturation vapor density

phase diagram

a graph of pressure vs. temperature of a particular substance, showing at which pressures and temperatures the three phases of the substance occur

PV diagram

a graph of pressure vs. volume

relative humidity

the amount of water in the air relative to the maximum amount the air can hold

saturation

the condition of 100% relative humidity

sublimation

the phase change from solid to gas

temperature

the quantity measured by a thermometer

thermal energy

$\overline{\text{KE}}$, the average translational kinetic energy of a molecule

thermal equilibrium

the condition in which heat no longer flows between two objects that are in contact; the two objects have the same temperature

thermal expansion

the change in size or volume of an object with change in temperature

thermal stress

stress caused by thermal expansion or contraction

triple point

the pressure and temperature at which a substance exists in equilibrium as a solid, liquid, and gas

vapor

a gas at a temperature below the boiling temperature

vapor pressure

the pressure at which a gas coexists with its solid or liquid phase

zeroth law of thermodynamics

law that states that if two objects are in thermal equilibrium, and a third object is in thermal equilibrium with one of those objects, it is also in thermal equilibrium with the other object