work done is the area under a graph of Fx(x) (Section 6.6)
heat capacity (Section 14.3)
the ideal gas law (Section 13.5)
specific heat of ideal gases at constant volume (Section 14.4)
natural logarithm (Appendix A.3)
Master the Concepts
The first law of thermodynamics is a statement of energy conservation: <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0073512141/663823/15_1.jpg','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (3.0K)</a>
where Q is the heat flow into the system and W is the work done on the system.
Pressure, temperature, volume, number of moles, internal energy, and entropy are state variables; they describe the state of a system at some instant of time but not how the system got to that state. Heat and work are not state variables—they describe how a system gets from one state to another.
The work done on a system when the pressure is constant—or for a volume change small enough that the pressure change is insignificant—is <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0073512141/663823/15_2.jpg','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (3.0K)</a>
The magnitude of the work done is the total area under the PV curve.
The change in internal energy of an ideal gas is determined solely by the temperature change. Therefore, <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0073512141/663823/15_10.jpg','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (6.0K)</a>
A process in which no heat is transferred into or out of the system is called an adiabatic process.
The molar specific heats of an ideal gas at constant volume and constant pressure are related by <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0073512141/663823/15_9.jpg','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (3.0K)</a>
Spontaneous heat flow from a hotter body to a colder body is always irreversible.
For one cycle of an engine, heat pump, or refrigerator, conservation of energy requires <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0073512141/663823/for_one_cycle.jpg','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (3.0K)</a>
where Q H, Q C, and W net are defined as positive quantities.
The efficiency of an engine is defined as <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0073512141/663823/15_12.jpg','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (3.0K)</a>
The coefficient of performance for a heat pump is <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0073512141/663823/15_15.jpg','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (6.0K)</a>
The coefficient of performance for a refrigerator or air conditioner is <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0073512141/663823/15_16.jpg','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (6.0K)</a>
A reservoir is a system with such a large heat capacity that it can exchange heat in either direction with a negligibly small temperature change.
The second law of thermodynamics can be stated in various equivalent ways. Two of them are: (1) heat never flows spontaneously from a colder body to a hotter body, and (2) the entropy of the universe never decreases.
The efficiency of a reversible engine is determined only by the absolute temperatures of the hot and cold reservoirs: <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=gif::::/sites/dl/free/0073512141/663823/15_17.gif','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (0.0K)</a>
If an amount of heat Q flows into a system at constant absolute temperature T, the entropy change of the system is <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0073512141/663823/15_20.jpg','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (3.0K)</a>
The third law of thermodynamics: it is impossible to cool a system to absolute zero.
