Brief Word about Units

The purpose of this chapter was to set the stage for learning about kinetics and to give a broad overview of the field of materials kinetics. The main points introduced in this chapter include  

Thermodynamics predicts whether a process i /tOMZfil happen, while kinetics predicts how fast it will happen. In the simplest terms, kinetics deals with rates. Additionally, kinetics describes how these rates are impacted by important system variables such as pressure, temperature, or concentration. 

When thermodynamics predicts that a process is favorable, this does not necessarily mean that it wZ/Z happen. There are many thermodynamically favorable processes that do not occur because the kinetic barriers are too high. A yes from thermodynamics really means maybe.  

Many kinetic phenomena can be described by basic concepts that broadly fall into one of two domains reaction processes and transport processes. Reaction kinetics describes the rates at which reactions occur while transport kinetics describes the rates at which matter (e.g., atoms or molecules), or charge, or energy is physically transported from one place to another. 

An overall kinetic process can often be broken down into a set of more detailed individual kinetic steps, some of which must occur in series, while others can take place in parallel. The overall rate for a process is determined by the interaction between all of these individual steps and is often governed by one step that is much slower than the others—this is known as the rate-limiting step. 

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A brief mention should be made about the terminology that has been used in the literature on the compressibilities of solutes in solution. The lUPAC "Quantities, Units and Symbols in Physical Chemistry" [93M] recommends that the name for the thermodynamic quantity Pt (or Ps) is the isothermal (or isentropic) compressibility. It also recommends that k is the symbol used to represent this quantity. In the chemical literature both and Px have been used as the symbols for the quantity -(l/V)(8V/8p)x, where x is either T or S, but in the biochemical literature Px has been used almost exclusively. For this reason we have chosen to use px in this review. The quantity Ps has sometimes been referred to as the adiabatic compressibility. The term adiabatic is loosely used in this context because isentropic does not mean adiabatic but adiabatic and reversible. The word compressibility has also been used in the chemical literature to name the thermodynamic quantity Kj,2 (Kt,2 = -(3V2/3p)x) which is commonly referred to as the partial molar isothermal compressibility. Similarly, in the study of protein solutions the same name has appeared in the biochemical literature to describe two different thermodynamic quantities. Both P and... 

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