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1: Introduction

Last updated

Apr 13, 2022
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- Licensing
- 1.1: Units

Howard DeVoe
University of Maryland

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$\newcommand{\id}{^{\text{id}}}      % ideal$
$\newcommand{\rf}{^{\text{ref}}}     % reference state$
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$\newcommand{\K}{\units{K}} % kelvins$
$\newcommand{\degC}{^\circ\text{C}} % degrees Celsius$
$\newcommand{\br}{\units{bar}} % bar (\bar is already defined)$
$\newcommand{\Pa}{\units{Pa}}$
$\newcommand{\mol}{\units{mol}} % mole$
$\newcommand{\V}{\units{V}} % volts$
$\newcommand{\timesten}[1]{\mbox{$\,\times\,10^{#1}$}}$
$\newcommand{\per}{^{-1}} % minus one power$
$\newcommand{\m}{_{\text{m}}} % subscript m for molar quantity$
$\newcommand{\CVm}{C_{V,\text{m}}} % molar heat capacity at const.V$
$\newcommand{\Cpm}{C_{p,\text{m}}} % molar heat capacity at const.p$
$\newcommand{\kT}{\kappa_T} % isothermal compressibility$
$\newcommand{\A}{_{\text{A}}} % subscript A for solvent or state A$
$\newcommand{\B}{_{\text{B}}} % subscript B for solute or state B$
$\newcommand{\bd}{_{\text{b}}} % subscript b for boundary or boiling point$
$\newcommand{\C}{_{\text{C}}} % subscript C$
$\newcommand{\f}{_{\text{f}}} % subscript f for freezing point$
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$\newcommand{\el}{\subs{el}} % electrical$
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Thermodynamics is a quantitative subject. It allows us to derive relations between the values of numerous physical quantities. Some physical quantities, such as a mole fraction, are dimensionless; the value of one of these quantities is a pure number. Most quantities, however, are not dimensionless and their values must include one or more units. This chapter reviews the SI system of units, which are the preferred units in science applications. The chapter then discusses some useful mathematical manipulations of physical quantities using quantity calculus, and certain general aspects of dimensional analysis.

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