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# Chapter 14: Thermodynamics

Difficulty Level: At Grade Created by: CK-12

Chapter Outline

### Chapter Summary

1. The ideal gas law states \begin{align*}PV=nRT\end{align*} where \begin{align*}P\end{align*} is pressure, \begin{align*}V\end{align*} is volume, \begin{align*}n\end{align*} is the number of moles of substance, \begin{align*}R\end{align*} is the universal gas constant and \begin{align*}T\end{align*} is temperature.

2. Thermodynamics is the study of processes in which energy is transferred by heat and work.

3. In an isothermal process, temperature is constant

4. In an isochoric process, volume is constant

5. In an isobaric process, pressure is constant

6. In an adiabatic process, no heat flows into or out of the system

7. The first law of thermodynamics: The change in the internal energy of a closed system is equal to the heat into (or out of) a system plus the work done on the system (or by the system).

\begin{align*}\Delta U=Q+W,\Delta U\end{align*} is the change in internal energy of the system, \begin{align*}Q\end{align*} is the heat, and \begin{align*}W\end{align*} the work.

8. The second law of thermodynamics describes the direction in which physical phenomena can occur.

Statements describing the second law:

a. Heat can flow spontaneously from hot to cold but never from cold to hot.

b. No heat machine is 100% efficient.

The most general statement of the second law:

For all natural processes, the total entropy of a system increases.

9. The efficiency of an actual heat engine can be expressed as

\begin{align*}e=\left(1-\frac{Q_L}{Q_H}\right) \times 100 \end{align*}

The high temperature thermal energy is \begin{align*}Q_H\end{align*} and the low temperature thermal energy is \begin{align*}Q_L\end{align*}.

10. The efficiency of a Carnot engine can be expressed as

\begin{align*}e=\left(1-\frac{T_L}{T_H}\right) \times 100 \end{align*}

The high operating temperature of the Carnot engine is \begin{align*}T_H\end{align*} and the low operating temperature of the Carnot engine \begin{align*}T_L\end{align*}.

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