Molecular theory of matter

The Kinetic Molecular Theory of matter attempts to describe all the states of matter and the conversion between the states by considering the structures of molecules comprising matter and how those molecules interact. There are three commonly encountered states of matter solids, liquids, and gases. There are a few other states of matter, such as plasmas, but these are encountered only under extremely high energy conditions. Therefore, we will restrict our conversation to the more mundane states. 

Rationalize the defining characteristics of the states of matter in terms of intermolecular forces and the kinetic molecular theory of matter. 

Let us first note that a given set of molecules does not always react, but rather that there are specific conditions which must be met in order that reactions proceed at a measurable rate. If we take temperature for consideration as a variable, we know that at low enough temperatures almost any chemical reaction may be stopped. But the molecular theory of matter has shown that temperature is simply an average measure of the mean energy of a molecule in thermal equilibrium. An increase in temperature implies an increase in molecular energy. 

This is a consequence of the fact that no thermodynamically exact method is known that allows the determination of individual ion activities. Thermodynamics is the systematic study of energy changes in chemical and physical systems, and as such is independent of models and theories, including the molecular theory of matter. Acknowledging the existence of dissociated ions in solution is necessary for many purposes, but is not necessary to the definition of thermodynamically exact quantities. ... 

This understanding was finally achieved in the quantum theory of 1925, which provided for the first time an adequate explanation of how matter is constructed of atoms and molecules, how atoms are constructed of nuclei and electrons, and how atoms interact with light. Each of the major developments of nineteenth-century physical science played critical roles in leading up to quantum theory. These developments included electromagnetic theory, molecular theory of matter, and statistical thermodynamics. ... 

The quantitative laws of chemical combination provide clear pointers to the molecular theory of matter, which increases progressively in vividness and realism with the application of Newton s laws to the motions of the particles. The interpretation of phenomena such as the pressure and viscosity of gases and the Brownian motion, and the assignment of definite magnitudes to molecular speeds, masses, and diameters render it clear that a continual interchange of energies must occur between the molecules of a material system, a circumstance which lies at the basis of temperature equilibrium and determines what in ordinary experience is called the flow of heat. It is responsible indeed for far more than this, and a large part of physical chemistry follows from the conception of the chaotic motion of the molecules. This matter must now be examined more deeply. 

At that time, the molecular theory of matter was not universally accepted. This had to wait for Einstein s 1905 explanation [32] of a study of the irregular movement of microscopic particles suspended in a liquid by the botanist Robert Brown [12] in 1828 - Brownian motion. Rutherford s 1911 paper [101] establishing the nuclear model of the atom was followed Bohr s quantum theory of the atom [8] and the flowering of Quantum Mechanics during the 1920s. Quantum ChemisUy, now mature field of scientific investigation and one of the centtal pillars of Computational Chemistty, was established in two seminal papers published in 1927 by Heitler and London [40] and Born and Qppenheimer [9]. 

In the case of nano (small) scale there is Uttle or no such data available and the molecular theories of matter in nanoscale are in their infancy. With the recent advent of tools to observe study and measure the behavior of matter in nanoscale it is expected that in a near future experimental nanoscale data will become available. 

A molecular theory of matter provides a bridge between the molecular properties of the individual particles constituting the system under observation and the macroscopic properties of the bulk matter as revealed in an actual experiment. The mathematical tools to establish such a bridge are contained within the realm of statistical mechanics. 

Demonstrate an understanding of the kinetic molecular theory of matter. 

SECTION 1 The Kinetic-Molecular Theory of Matter KEY TERMS ... 

I just want to say that even at this early stage, simple molecular ideas can do much to stretch the range of application of thermodynamics. When thermodynamics is coupled with the molecular theory of matter, we can construct useful models while these only roughly approximate true molecular behavior, they nevertheless enable us to interpolate and extrapolate with some confidence, thereby reducing further the experimental effort required for reliable results. When my nontechnical friends ask me what I, a molecular thermodynamicist do, I answer with a naive but essentially accurate analogy I am a greedy tax collector. From the smallest possible capital, I try to extract the largest possible revenue. 

Risteen, A.D. (1895) Molecules and the Molecular Theory of Matter, Ginn and Company. 

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