3: First Law of Thermodynamics
- Page ID
- 84308
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Thermodynamics is the study of how energy flows into and out of systems and how it flows through the universe. People have been studying thermodynamics for a very long time and have developed the field a great deal, including the incorporation of high-level mathematics into the process. Many of the relationships may look cumbersome or complicated, but they are always describing the same basic thing: the flow of energy through the universe.
- 3.1: Prelude to Thermodynamics
- The text discusses thermodynamics, highlighting a quote from Albert Einstein praising the simplicity and universality of its laws. Thermodynamics is the study of energy flow in systems and the universe, often involving complex relationships related to basic energy principles. It plays a crucial role in processes like powering cars, electronics, and heating.
- 3.2: Work and Heat
- The text discusses the contributions of James P. Joule to modern thermodynamics, particularly his experiments demonstrating that work and heat can both change a system's temperature, forming the basis for the First Law of Thermodynamics. The law suggests that a system's capacity to do work is increased by heating or working on it, and it defines internal energy change as the sum of heat (q) and work (w).
- 3.3: Reversible and Irreversible Pathways
- The page explains the concept of work in systems with a focus on expansion work, distinguishing between reversible and irreversible expansion. Reversible expansion is equated with a scenario where the external and internal pressures are equal, allowing work calculations using ideal gas equations. Examples illustrate calculations of work, internal energy, heat, and enthalpy for isothermal, isobaric, and adiabatic processes.
- 3.4: Calorimetry
- This page discusses the importance of understanding thermodynamics in chemical reactions, particularly focusing on calorimetry to measure the heat exchange (\(q\)) during chemical reactions. It outlines the use of bomb calorimetry, which is typically employed for combustion reactions. The process involves calculating the change in internal energy using a bomb calorimeter and examples to determine the enthalpy of combustion for substances.
- 3.5: Temperature Dependence of Enthalpy
- The document provides a guide on calculating thermodynamic functions like enthalpy at temperatures not readily available in tabulated data. It explains how to adapt Kirchhoff's Law to account for the temperature dependence of heat capacity, incorporating an empirical model for \(C_p(T)\) involving parameters \(a\), \(b\), and \(c\).
- 3.6: Reaction Enthalpies
- Reaction enthalpies are important, but difficult to tabulate. However, because enthalpy is a state function, it is possible to use Hess’ Law to simplify the tabulation of reaction enthalpies. Hess’ Law is based on the addition of reactions. By knowing the reaction enthalpy for constituent reactions, the enthalpy of a reaction that can be expressed as the sum of the constituent reactions can be calculated.
- 3.7: Lattice Energy and the Born-Haber Cycle
- The page discusses the concept of lattice energy, which is the energy required to convert one mole of a crystalline solid to gaseous ions. It explains the Born-Haber Cycle, a thermodynamic cycle used to visualize enthalpy changes in the formation of an ionic solid, specifically \(\ce{NaCl}\). The cycle involves multiple pathways and steps, including sublimation, ionization, and electron affinity, culminating in lattice energy.
- 3.E: First Law of Thermodynamics (Exercises)
- This page contains a series of thermodynamics problems, primarily related to calculations involving gases and heat reactions, such as the temperature change in a heating experiment, and changes in pressure, work, internal energy, and enthalpy for various gas expansions under different conditions (isothermal, isochoric, isobaric, and adiabatic).
- 3.S: First Law of Thermodynamics (Summary)
- This page outlines the learning objectives and key concepts for mastering thermodynamics, including defining internal energy, work, heat, and enthalpy. It also covers calculating energy changes in systems using variables like temperature, pressure, and volume in different pathways. The content emphasizes understanding and using calorimetry, formation reactions, bond dissociation energies, and phase change enthalpies.