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A mole of any substance has a mass in grams equal to its molecular weight, which can be determined from the periodic table of elements. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
The ideal gas law can also be written and solved in terms of the number of moles of gas:PV=nRT,PV=nRT,wherennis number of moles andRRis the universal gas constant,R=8.31J/molâK.R=8.31J/molâK. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
The ideal gas law is generally valid at temperatures well above the boiling temperature. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
Kinetic theory is the atomistic description of gases as well as liquids and solids. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
Kinetic theory models the properties of matter in terms of continuous random motion of atoms and molecules. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
The ideal gas law can also be expressed asPV=13Nmv2¯,PV=13Nmv2¯,wherePPis the pressure (average force per unit area),VVis the volume of gas in the container,NNis the number of molecules in the container,mmis the mass of a molecule, andv2¯v2¯is the average of the molecular speed squared. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
Thermal energy is defined to be the average translational kinetic energyKE¯KE¯of an atom or molecule. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
The temperature of gases is proportional to the average translational kinetic energy of atoms and molecules.KE¯=12mv2¯=32kTKE¯=12mv2¯=32kTorv2¯=vrms=3kTm.v2¯=vrms=3kTm. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
or | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
The motion of individual molecules in a gas is random in magnitude and direction. However, a gas of many molecules has a predictable distribution of molecular speeds, known as theMaxwell-Boltzmann distribution. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
Most substances have three distinct phases: gas, liquid, and solid. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
Phase changes among the various phases of matter depend on temperature and pressure. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
The existence of the three phases with respect to pressure and temperature can be described in a phase diagram. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
Two phases coexist (i.e., they are in thermal equilibrium) at a set of pressures and temperatures. These are described as a line on a phase diagram. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
The three phases coexist at a single pressure and temperature. This is known as the triple point and is described by a single point on a phase diagram. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
A gas at a temperature below its boiling point is called a vapor. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
Vapor pressure is the pressure at which a gas coexists with its solid or liquid phase. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
Partial pressure is the pressure a gas would create if it existed alone. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
Daltonâs law states that the total pressure is the sum of the partial pressures of all of the gases present. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
Relative humidity is the fraction of water vapor in a gas compared to the saturation value. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
The saturation vapor density can be determined from the vapor pressure for a given temperature. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
Percent relative humidity is defined to bepercent relative humidity=vapor densitysaturation vapor densityÃ100.percent relative humidity=vapor densitysaturation vapor densityÃ100. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
The dew point is the temperature at which air reaches 100% relative humidity. | https://openstax.org/books/college-physics-2e/pages/13-section-summary |
conduction : heat transfer through stationary matter by physical contact | https://openstax.org/books/college-physics-2e/pages/14-glossary |
convection : heat transfer by the macroscopic movement of fluid | https://openstax.org/books/college-physics-2e/pages/14-glossary |
emissivity : measure of how well an object radiates | https://openstax.org/books/college-physics-2e/pages/14-glossary |
greenhouse effect : warming of the Earth that is due to gases such as carbon dioxide and methane that absorb infrared radiation from the Earthâs surface and reradiate it in all directions, thus sending a fraction of it back toward the surface of the Earth | https://openstax.org/books/college-physics-2e/pages/14-glossary |
heat : the spontaneous transfer of energy due to a temperature difference | https://openstax.org/books/college-physics-2e/pages/14-glossary |
heat of sublimation : the energy required to change a substance from the solid phase to the vapor phase | https://openstax.org/books/college-physics-2e/pages/14-glossary |
kilocalorie : 1kilocalorie=1000calories1kilocalorie=1000calories | https://openstax.org/books/college-physics-2e/pages/14-glossary |
latent heat coefficient : a physical constant equal to the amount of heat transferred for every 1 kg of a substance during the change in phase of the substance | https://openstax.org/books/college-physics-2e/pages/14-glossary |
mechanical equivalent of heat : the work needed to produce the same effects as heat transfer | https://openstax.org/books/college-physics-2e/pages/14-glossary |
net rate of heat transfer by radiation : isQnett=ÏeAT24âT14Qnett=ÏeAT24âT14 | https://openstax.org/books/college-physics-2e/pages/14-glossary |
Rfactor : the ratio of thickness to the conductivity of a material | https://openstax.org/books/college-physics-2e/pages/14-glossary |
radiation : energy transferred by electromagnetic waves directly as a result of a temperature difference | https://openstax.org/books/college-physics-2e/pages/14-glossary |
radiation : heat transfer which occurs when microwaves, infrared radiation, visible light, or other electromagnetic radiation is emitted or absorbed | https://openstax.org/books/college-physics-2e/pages/14-glossary |
rate of conductive heat transfer : rate of heat transfer from one material to another | https://openstax.org/books/college-physics-2e/pages/14-glossary |
specific heat : the amount of heat necessary to change the temperature of 1.00 kg of a substance by 1.00 ºC | https://openstax.org/books/college-physics-2e/pages/14-glossary |
Stefan-Boltzmann law of radiation : Qt=ÏeAT4,Qt=ÏeAT4,whereÏÏis the Stefan-Boltzmann constant,AAis the surface area of the object,TTis the absolute temperature, andeeis the emissivity | https://openstax.org/books/college-physics-2e/pages/14-glossary |
sublimation : the transition from the solid phase to the vapor phase | https://openstax.org/books/college-physics-2e/pages/14-glossary |
thermal conductivity : the property of a materialâs ability to conduct heat | https://openstax.org/books/college-physics-2e/pages/14-glossary |
Heat and work are the two distinct methods of energy transfer. | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
Heat is energy transferred solely due to a temperature difference. | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
Any energy unit can be used for heat transfer, and the most common are kilocalorie (kcal) and joule (J). | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
Kilocalorie is defined to be the energy needed to change the temperature of 1.00 kg of water between14.5ºC14.5ºCand15.5ºC15.5ºC. | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
The mechanical equivalent of this heat transfer is1.00 kcal=4186 J.1.00 kcal=4186 J. | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
The transfer of heatQQthat leads to a changeÎTÎTin the temperature of a body with massmmisQ=mcÎTQ=mcÎT, whereccis the specific heat of the material. This relationship can also be considered as the definition of specific heat. | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
Most substances can exist either in solid, liquid, and gas forms, which are referred to as âphases.â | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
Phase changes occur at fixed temperatures for a given substance at a given pressure, and these temperatures are called boiling and freezing (or melting) points. | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
During phase changes, heat absorbed or released is given by:Q=mL,Q=mL,whereLLis the latent heat coefficient. | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
whereLLis the latent heat coefficient. | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
Heat is transferred by three different methods: conduction, convection, and radiation. | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
Heat conduction is the transfer of heat between two objects in direct contact with each other. | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
The rate of heat transferQ/tQ/t(energy per unit time) is proportional to the temperature differenceT2âT1T2âT1and the contact areaAAand inversely proportional to the distanceddbetween the objects:Qt=kAT2âT1d.Qt=kAT2âT1d. | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
Convection is heat transfer by the macroscopic movement of mass. Convection can be natural or forced and generally transfers thermal energy faster than conduction.Table 14.4gives wind-chill factors, indicating that moving air has the same chilling effect of much colder stationary air.Convection that occurs along with a... | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
Radiation is the rate of heat transfer through the emission or absorption of electromagnetic waves. | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
The rate of heat transfer depends on the surface area and the fourth power of the absolute temperature:Qt=ÏeAT4,Qt=ÏeAT4,whereÏ=5.67Ã10â8J/sâm2âK4Ï=5.67Ã10â8J/sâm2âK4is the Stefan-Boltzmann constant andeeis the emissivity of the body. For a black body,e=1e=1whereas a shiny white or perfect reflector hase=... | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
whereÏ=5.67Ã10â8J/sâm2âK4Ï=5.67Ã10â8J/sâm2âK4is the Stefan-Boltzmann constant andeeis the emissivity of the body. For a black body,e=1e=1whereas a shiny white or perfect reflector hase=0e=0, with real objects having values ofeebetween 1 and 0. The net rate of heat transfer by radiation is | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
whereT1T1is the temperature of an object surrounded by an environment with uniform temperatureT2T2andeeis the emissivity of theobject. | https://openstax.org/books/college-physics-2e/pages/14-section-summary |
adiabatic process : a process in which no heat transfer takes place | https://openstax.org/books/college-physics-2e/pages/15-glossary |
Carnot cycle : a cyclical process that uses only reversible processes, the adiabatic and isothermal processes | https://openstax.org/books/college-physics-2e/pages/15-glossary |
Carnot efficiency : the maximum theoretical efficiency for a heat engine | https://openstax.org/books/college-physics-2e/pages/15-glossary |
Carnot engine : a heat engine that uses a Carnot cycle | https://openstax.org/books/college-physics-2e/pages/15-glossary |
change in entropy : the ratio of heat transfer to temperatureQ/TQ/T | https://openstax.org/books/college-physics-2e/pages/15-glossary |
coefficient of performance : for a heat pump, it is the ratio of heat transfer at the output (the hot reservoir) to the work supplied; for a refrigerator or air conditioner, it is the ratio of heat transfer from the cold reservoir to the work supplied | https://openstax.org/books/college-physics-2e/pages/15-glossary |
cyclical process : a process in which the path returns to its original state at the end of every cycle | https://openstax.org/books/college-physics-2e/pages/15-glossary |
entropy : a measurement of a system's disorder and its inability to do work in a system | https://openstax.org/books/college-physics-2e/pages/15-glossary |
first law of thermodynamics : states that the change in internal energy of a system equals the net heat transferintothe system minus the net work donebythe system | https://openstax.org/books/college-physics-2e/pages/15-glossary |
heat engine : a machine that uses heat transfer to do work | https://openstax.org/books/college-physics-2e/pages/15-glossary |
heat pump : a machine that generates heat transfer from cold to hot | https://openstax.org/books/college-physics-2e/pages/15-glossary |
human metabolism : conversion of food into heat transfer, work, and stored fat | https://openstax.org/books/college-physics-2e/pages/15-glossary |
internal energy : the sum of the kinetic and potential energies of a systemâs atoms and molecules | https://openstax.org/books/college-physics-2e/pages/15-glossary |
irreversible process : any process that depends on path direction | https://openstax.org/books/college-physics-2e/pages/15-glossary |
isobaric process : constant-pressure process in which a gas does work | https://openstax.org/books/college-physics-2e/pages/15-glossary |
isochoric process : a constant-volume process | https://openstax.org/books/college-physics-2e/pages/15-glossary |
isothermal process : a constant-temperature process | https://openstax.org/books/college-physics-2e/pages/15-glossary |
macrostate : an overall property of a system | https://openstax.org/books/college-physics-2e/pages/15-glossary |
microstate : each sequence within a larger macrostate | https://openstax.org/books/college-physics-2e/pages/15-glossary |
Otto cycle : a thermodynamic cycle, consisting of a pair of adiabatic processes and a pair of isochoric processes, that converts heat into work, e.g., the four-stroke engine cycle of intake, compression, ignition, and exhaust | https://openstax.org/books/college-physics-2e/pages/15-glossary |
reversible process : a process in which both the heat engine system and the external environment theoretically can be returned to their original states | https://openstax.org/books/college-physics-2e/pages/15-glossary |
second law of thermodynamics : heat transfer flows from a hotter to a cooler object, never the reverse, and some heat energy in any process is lost to available work in a cyclical process | https://openstax.org/books/college-physics-2e/pages/15-glossary |
second law of thermodynamics stated in terms of entropy : the total entropy of a system either increases or remains constant; it never decreases | https://openstax.org/books/college-physics-2e/pages/15-glossary |
statistical analysis : using statistics to examine data, such as counting microstates and macrostates | https://openstax.org/books/college-physics-2e/pages/15-glossary |
The first law of thermodynamics is given asÎEint=QâWÎEint=QâW, whereÎEintÎEintis the change in internal energy of a system,QQis the net heat transfer (the sum of all heat transfer into and out of the system), andWWis the net work done (the sum of all work done on or by the system). | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
BothQQandWWare energy in transit; onlyÎEintÎEintrepresents an independent quantity capable of being stored. | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
The internal energyEintEintof a system depends only on the state of the system and not how it reached that state. | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
Metabolism of living organisms, and photosynthesis of plants, are specialized types of heat transfer, doing work, and internal energy of systems. | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
One of the important implications of the first law of thermodynamics is that machines can be harnessed to do work that humans previously did by hand or by external energy supplies such as running water or the heat of the Sun. A machine that uses heat transfer to do work is known as a heat engine. | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
There are several simple processes, used by heat engines, that flow from the first law of thermodynamics. Among them are the isobaric, isochoric, isothermal and adiabatic processes. | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
These processes differ from one another based on how they affect pressure, volume, temperature, and heat transfer. | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
If the work done is performed on the outside environment, work (WW) will be a positive value. If the work done is done to the heat engine system, work (WW) will be a negative value. | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
Some thermodynamic processes, including isothermal and adiabatic processes, are reversible in theory; that is, both the thermodynamic system and the environment can be returned to their initial states. However, because of loss of energy owing to the second law of thermodynamics, complete reversibility does not work in ... | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
The two expressions of the second law of thermodynamics are: (i) Heat transfer occurs spontaneously from higher- to lower-temperature bodies but never spontaneously in the reverse direction; and (ii) It is impossible in any system for heat transfer from a reservoir to completely convert to work in a cyclical process in... | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
Irreversible processes depend on path and do not return to their original state. Cyclical processes are processes that return to their original state at the end of every cycle. | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
In a cyclical process, such as a heat engine, the net work done by the system equals the net heat transfer into the system, orW=QhâQcW=QhâQc, whereQhQhis the heat transfer from the hot object (hot reservoir), andQcQcis the heat transfer into the cold object (cold reservoir). | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
Efficiency can be expressed asEff=WQhEff=WQh, | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
the ratio of work output divided by the amount of energy input. | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
The four-stroke gasoline engine is often explained in terms of the Otto cycle, which is a repeating sequence of processes that convert heat into work. | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
The Carnot cycle is a theoretical cycle that is the most efficient cyclical process possible. Any engine using the Carnot cycle, which uses only reversible processes (adiabatic and isothermal), is known as a Carnot engine. | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
Any engine that uses the Carnot cycle enjoys the maximum theoretical efficiency. | https://openstax.org/books/college-physics-2e/pages/15-section-summary |
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