Key Terms

Key Terms

absolute temperature scale

scale, such as Kelvin, with a zero point that is absolute zero

absolute zero

temperature at which the average kinetic energy of molecules is zero

calorie (cal)

energy needed to change the temperature of 1.00 g of water by $1.00\text{°}\text{C}$

calorimeter

container that prevents heat transfer in or out

calorimetry

study of heat transfer inside a container impervious to heat

Celsius scale

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

coefficient of linear expansion

($\alpha$) material property that gives the change in length, per unit length, per $1\text{-}\text{°}\text{C}$ change in temperature; a constant used in the calculation of linear expansion; the coefficient of linear expansion depends to some degree on the temperature of the material

coefficient of volume expansion

($\beta$) similar to $\alpha$ but gives the change in volume, per unit volume, per $1\text{-}\text{°}\text{C}$ change in temperature

conduction

heat transfer through stationary matter by physical contact

convection

heat transfer by the macroscopic movement of fluid

critical point

for a given substance, the combination of temperature and pressure above which the liquid and gas phases are indistinguishable

critical pressure

pressure at the critical point

critical temperature

temperature at the critical point

degree Celsius

($\text{°}\text{C}$) unit on the Celsius temperature scale

degree Fahrenheit

($\text{°}\text{F}$) unit on the Fahrenheit temperature scale

emissivity

measure of how well an object radiates

Fahrenheit scale

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

greenhouse effect

warming of the earth that is due to gases such as carbon dioxide and methane that absorb infrared radiation from Earth’s surface and reradiate it in all directions, thus sending some of it back toward Earth

heat

energy transferred solely due to a temperature difference

heat of fusion

energy per unit mass required to change a substance from the solid phase to the liquid phase, or released when the substance changes from liquid to solid

heat of sublimation

energy per unit mass required to change a substance from the solid phase to the vapor phase

heat of vaporization

energy per unit mass required to change a substance from the liquid phase to the vapor phase

heat transfer

movement of energy from one place or material to another as a result of a difference in temperature

Kelvin scale (K)

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

kilocalorie (kcal)

energy needed to change the temperature of 1.00 kg of water between $14.5\text{°}\text{C}$ and $15.5\text{°}\text{C}$

latent heat coefficient

general term for the heats of fusion, vaporization, and sublimation

mechanical equivalent of heat

work needed to produce the same effects as heat transfer

net rate of heat transfer by radiation

$P_{\text{net}}=\sigma eA\left(T_2{}^4-T_1{}^4\right)$

phase diagram

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

radiation

energy transferred by electromagnetic waves directly as a result of a temperature difference

rate of conductive heat transfer

rate of heat transfer from one material to another

specific heat

amount of heat necessary to change the temperature of 1.00 kg of a substance by $1.00\text{°}\text{C}$; also called “specific heat capacity”

Stefan-Boltzmann law of radiation

$P=\sigma Ae{T}^4,$ where $\sigma =5.67\times {10}^{\mathrm{-8}}\text{J/s}·{\text{m}}^2·{\text{K}}^4$ is the Stefan-Boltzmann constant, A is the surface area of the object, T is the absolute temperature, and e is the emissivity

sublimation

phase change from solid to gas

temperature

functionally defined as a quantity measured by a thermometer, which, at least for most of the systems discussed in this chapter, reflects the mechanical energy of particles in the system

thermal conductivity

property of a material describing its ability to conduct heat

thermal equilibrium

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

thermal expansion

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

thermal stress

stress caused by thermal expansion or contraction

triple point

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

vapor

gas at a temperature below the critical temperature

vapor pressure

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