chap 13

• absolute zero the lowest possible temperature; the temperature at which all molecular motion ceases
• Avogadro’s number , the number of molecules or atoms in one mole of a substance; particles/mole
• Boltzmann constant , a physical constant that relates energy to temperature;
• Celsius scale temperature scale in which the freezing point of water is and the boiling point of water i
• coefficient of linear expansion , the change in length, per unit length, per 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
• 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 exis
• 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 and the boiling point of water is 212F
• 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 , 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