Physical Chemistry

11 Key excerpts on "Physical Chemistry"

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  Cross Disciplinary Physics

  • (Author)
  • 2014(Publication Date)
  • Learning Press

    (Publisher)

  ________________________ WORLD TECHNOLOGIES ________________________ Chapter- 2 Chemical Physics Chemical physics is a subdiscipline of chemistry and physics that investigates physic-cochemical phenomena using techniques from atomic and molecular physics and condensed matter physics; it is the branch of physics that studies chemical processes from the point of view of physics. While at the interface of physics and chemistry, chemical physics is distinct from Physical Chemistry in that it focuses more on the characteristic elements and theories of physics. Meanwhile, Physical Chemistry studies the physical nature of chemistry. Nonetheless, the distinction between the two fields is vague, and workers often practice in each field during the course of their research. What chemical physicists do Chemical physicists commonly probe the structure and dynamics of ions, free radicals, polymers, clusters, and molecules. Areas of study include the quantum mechanical behavior of chemical reactions, the process of solvation, inter- and intra-molecular energy flow, and single entities such as quantum dots. Experimental chemical physicists use a variety of spectroscopic techniques to better understand hydrogen bonding, electron transfer, the formation and dissolution of chemical bonds, chemical reactions, and the formation of nanoparticles. Theoretical chemical physicists create simulations of the molecular processes probed in these experiments to both explain results and guide future investigations. The goals of chemical physics research include understanding chemical structures and reactions at the quantum mechanical level, elucidating the structure and reactivity of gas phase ions and radicals, and discovering accurate approximations to make the physics of chemical phenomena computationally accessible.

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  Chemical Physics & Physical Chemistry

  • (Author)
  • 2014(Publication Date)
  • Library Press

    (Publisher)

  ________________________ WORLD TECHNOLOGIES ________________________ Chapter- 1 Chemical Physics and Physical Chemistry Chemical physics Chemical physics is a subdiscipline of chemistry and physics that investigates physi-cochemical phenomena using techniques from atomic and molecular physics and condensed matter physics; it is the branch of physics that studies chemical processes from the point of view of physics. While at the interface of physics and chemistry, chemical physics is distinct from Physical Chemistry in that it focuses more on the characteristic elements and theories of physics. Meanwhile, Physical Chemistry studies the physical nature of chemistry. Nonetheless, the distinction between the two fields is vague, and workers often practice in each field during the course of their research. What chemical physicists do Chemical physicists commonly probe the structure and dynamics of ions, free radicals, polymers, clusters, and molecules. Areas of study include the quantum mechanical behavior of chemical reactions, the process of solvation, inter- and intra-molecular energy flow, and single entities such as quantum dots. Experimental chemical physicists use a variety of spectroscopic techniques to better understand hydrogen bonding, electron transfer, the formation and dissolution of chemical bonds, chemical reactions, and the formation of nanoparticles. Theoretical chemical physicists create simulations of the molecular processes probed in these experiments to both explain results and guide future investigations. The goals of chemical physics research include understanding chemical structures and reactions at the quantum mechanical level, elucidating the structure and reactivity of gas phase ions and radicals, and discovering accurate approximations to make the physics of chemical phenomena computationally accessible.

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  Modern and Cross Disciplinary Physics

  • (Author)
  • 2014(Publication Date)
  • Academic Studio

    (Publisher)

  Physical Chemistry, in contrast to chemical physics, is predominantly (but not always) a macroscopic or supra-molecular science, as the majority of the principles on which Physical Chemistry was founded are concepts related to the bulk rather than on molecular/ atomic structure alone; for example, chemical equilibrium, colloids, etc. Some of the relationships that Physical Chemistry strives to resolve include the effects of: 1. Intermolecular forces on the physical properties of materials (plasticity, tensile strength, surface tension in liquids). 2. Reaction kinetics on the rate of a reaction. 3. The identity of ions on the electrical conductivity of materials. 4. Surface chemistry and electrochemistry of membranes. History The term Physical Chemistry was first introduced by Mikhail Lomonosov in 1752, when he presented a lecture course entitled A Course in True Physical Chemistry (Russian: «Курс истинной физической химии») before the students of Petersburg University. Modern Physical Chemistry originated in the 1860s to 1880s with work on chemical thermodynamics, electrolytes in solutions, chemical kinetics and other subjects. One milestone was the publication in 1876 by Josiah Willard Gibbs of his paper, On the Equilibrium of Heterogeneous Substances . This paper introduced several of the corner-stones of Physical Chemistry, such as Gibbs energy, chemical potentials, Gibbs phase rule . Other milestones include the subsequent naming and accreditation of enthalpy to Heike Kamerlingh Onnes and to macromolecular processes. The first scientific journal specifically in the field of Physical Chemistry was the German journal, Zeitschrift für Physikalische Chemie , founded in 1887 by Wilhelm Ostwald and Jacobus Henricus van 't Hoff. Together with Svante August Arrhenius., these were the leading figures in Physical Chemistry in the late 19th century and early 20th century. All three were awarded with the Nobel Prize in Chemistry between 1901-1909.

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  Molecular Physical Chemistry

  A Concise Introduction

  • Keith A McLauchlan(Author)
  • 2007(Publication Date)
  • Royal Society of Chemistry

    (Publisher)

  MMMM CHAPTER 1 Some Basic Ideas and Examples 1.1 INTRODUCTION Physical Chemistry is widely perceived as a collection of largely indepen-dent topics, few of which appear straightforward. This book aims to remove this misconception by basing it securely on the atoms and mol-ecules that constitute matter, and their properties. We shall concentrate on just two aspects and we focus mainly on thermodynamics, which although extremely powerful is one of the least popular subjects with students. A briefer account describes how reactions occur. We shall nevertheless encounter the major building blocks of Physical Chemistry, the foundations that, if understood, together with their inter-dependence, remove any mystique. These include statistical thermodynamics, ther-modynamics and quantum theory. The way that Physical Chemistry is taught today reflects the historical process by which understanding was initially obtained. One subject led to another, not necessarily with any underlying philosophical connection but largely as a result of what was possible at the time. All experiments involved very large numbers of molecules (although when ther-modynamics was first formulated the existence of atoms and molecules was not generally accepted) and people attempted to decipher what happened at a molecular level from their results. This was very indirect. Nowadays the existence and properties of atoms and molecules are established and experiments can even be performed on individual atoms and molecules. This provides the opportunity for a different way of looking at the subject, building from these properties to deduce the characteristic behaviour of large collections of them, which is more in keeping with how chemistry is taught at school level. Similarly, our understanding of how reactions occur has come from observations of samples containing huge numbers of molecules and we have tried to deduce what happens at molecular level from them.

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  Basic Physical Chemistry

  The Route to Understanding

  • E Brian Smith(Author)
  • 2012(Publication Date)
  • ICP

    (Publisher)

  1 Background 1.1 Introduction The boundaries of scientific subjects are defined only by usage. They change with time and so it is rarely worthwhile to seek detailed definitions. However, it can be said that chemistry is the study of the structure, composition and transformations of substances and we may take this as a useful working definition that will serve our purpose. Physical Chemistry seeks to provide a quantitative understanding of chemistry. To do this requires an understanding of the structure of matter, of how atoms combine to form molecules and, when chemical compounds react, what determines the speed of reaction and what new substances result. We need to answer questions such as: (i) why are there approximately one hundred elements each with different properties but with clear family relationships? (ii) how are stable chemical compounds formed and what factors contribute to their stability? (iii) why, when substances are exposed to light (or other radiation), are only some wavelengths absorbed, which may or may not induce chemical change? (iv) why do some compounds react rapidly and completely to produce new substances and others do not react at all? (v) why some compounds which can, in principle, react to produce a new stable product, do not do so, or at least react only very slowly? (vi) why can substances exist in the gas, liquid or solid states? It is possible to approach the subject of Physical Chemistry by reviewing the experimental evidence which provides the facts on which chemical theories must be based. An alternative approach starts with the theories that have been developed and seeks to interpret chemical phenomena on the basis of these theories. Given ample time and space, there is much to be said for the first approach because it corresponds to the way in which our understanding of chemistry has developed. However, given very limited space and time, it is much more economical to take the second approach 1

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  The Handy Chemistry Answer Book

  • Justin P. Lomont, Ian C. Stewart(Authors)
  • 2013(Publication Date)
  • Visible Ink Press

    (Publisher)

  PHYSICAL AND THEORETICAL CHEMISTRY

  ENERGY IS EVERYTHING

  What is Physical Chemistry?

  Physical Chemistry is a branch of chemistry primarily concerned with developing a better understanding of the fundamental principles that govern chemical processes. It is an empirical science, meaning that it is based on experimental observations, though it is probably the most closely linked experimental branch of chemistry to developing new theories in chemistry. As the name implies, Physical Chemistry is intrinsically concerned with topics in physics that are also relevant to the study of chemistry.

  What is energy?

  In chemistry, energy serves as the “currency” for making or breaking chemical bonds and moving molecules (or matter) from one place to another.

  What is potential energy?

  Potential energy describes all of the nonkinetic energy associated with an object. This energy can be the energy stored in chemical bonds, in a compressed spring, or in a variety of other ways. Another example is gravitational potential energy, like that associated with a ball sitting at the top of a hill. Since there are many types of potential energy, there isn’t a single equation that describes them all. Since the value we assign to potential energy is always inherently described relative to some choice of a reference value, we can only actually measure changes in potential energy in a meaningful way. A closed system can exchange potential energy for kinetic and vice versa, but the total energy must always remain constant. This is stated in the First Law of Thermodynamics, which we’ll get to soon.

  What is kinetic energy?

  Kinetic energy is the type of energy associated with the movement of an object. Faster-moving objects have more kinetic energy, and the kinetic energy of an object is related to its mass, m, and velocity, v, by the equation:

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  Fundamentals of Molecular Structural Biology

  • Subrata Pal(Author)
  • 2019(Publication Date)
  • Academic Press

    (Publisher)

  Chapter 3

  Physical basis of chemistry

  Abstract

  Physics has been the chief agent in transforming molecular biology into molecular structural biology. This chapter gives an overview of different areas of physics as a minimum requirement for the experimental and theoretical understanding of biomolecular interactions and dynamics. The layout of the topics is somewhat similar to one that would appear in an exclusive textbook on basic physics—classical mechanics, wave motion, kinetic theory and thermodynamics, and quantum and statistical physics; nevertheless, the presentation here is purely introductory. In each of the topics, mathematical expressions and equations have been judiciously used to deliver some quantitative sense. All such is expected to facilitate meaningful deliberations in the subsequent chapters.

  Keywords

  Classical mechanics; Wave motion; Kinetic theory and thermodynamics; Quantum physics; Statistics

  Richard Feynman, Nobel Laureate in Physics in 1965, had said, “there is nothing that living things do that cannot be understood from the point of view that they are made of atoms acting according to the laws of physics.” On the one hand, physics has provided very powerful techniques such as X-ray crystallography, a wide variety of spectroscopy, and electron microscopy to investigate the biological system at the atomic level. At the same time, physics has also placed chemistry on a sound theoretical foundation from where it has been able to characterize complex molecules and unravel intricate molecular mechanisms of life.

  3.1 Classical mechanics

  3.1.1 Matter and motion

  Let us begin by considering an object in motion. The simplest object would be a dimensionless particle. At any particular time t , the location of the particle can be denoted by the position vector r :

  r = x

  i ˆ

  + y

  j ˆ

  + z

  k ˆ

    (3.1)

  where

  i ˆ

  ,

  j ˆ

  , and

  k ˆ

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  Physical Chemistry from Ostwald to Pauling

  The Making of a Science in America

  • John W. Servos(Author)
  • 2021(Publication Date)
  • Princeton University Press

    (Publisher)

  Instances of both cooperation and conflict are readily visible in relations between physical chemists and chemical engineers in the era of World War I. They were drawn together by self-interest. Physical chemists saw in chemical engineers a potentially large clientele and an opportunity to influence the world of business. Chemical engineers recognized in Physical Chemistry tools of industrial value. “Physical Chemistry,” wrote one,

  is described as that branch of chemistry which has for its object the study of the laws governing chemical phenomena. When these laws and their application to a reaction or process are once understood, it is a relatively easy matter to select the most favorable working conditions in an apparatus which operates on an industrial scale.1

  “To be able to actually apply the laws of chemistry and to predict the course of reactions from general principles already proven,” wrote another, “is a tremendous economy of both time and energy.”2

  Yet, characteristically, the engineer’s emphasis was on efficiency rather than understanding. “The owners of electrochemical industries,” wrote Charles Burgess, a founder of Wisconsin’s program in chemical engineering,

  are not advertising for men to determine the dissociation constants at extreme dilution, or to measure solution tensions and osmotic pressures under ideal conditions, or to determine the velocity of migration of ions; but, rather, men who can operate machinery, and design and work electrolytic appliances so that a kilowatt hour may be made to do the greatest service.3

  Burgess required students to take a semester of work with Louis Kahlenberg, Wisconsin’s physical chemist. But one semester was rather too little to suit Kahlenberg, who soon launched a competitive program in industrial chemistry, and rather too much for some of Burgess’s students, who grumbled about Kahlenberg’s antagonistic attitude toward engineers. Chemical engineers and physical chemists grew increasingly interdependent in the early twentieth century, but at Wisconsin, and at other universities, mutual interests did not always guarantee harmonious relations.4

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  Chemistry for Environmental Scientists

  • Detlev Möller(Author)
  • 2015(Publication Date)
  • De Gruyter

    (Publisher)

  3 Fundamentals of Physical Chemistry

  Transport and transformation of chemical species is ongoing permanently in the environment, within soils, waters and air as well as crossing the reservoir interfaces. As already stated, the atmosphere is the global reservoir, characterised with the highest rates of turnover. The Earth’s surface (soils, waters and vegetation) is the source of atmospheric constituents but is also the disposal site of air pollutants (after deposition) and direct pollution from wastewater, landfills, agrochemicals, and other human activities. As often already mentioned in this book, we cannot separate chemical and physical processes, but this book will not refer to transport processes with the exception of molecular diffusion to interfaces.

  Physical Chemistry describes particulate phenomena in chemical systems in terms of laws and concepts of physics.

  Normally, into the complex term Physical Chemistry also fall the key properties of ‘environmental’ materials we have discussed in the previous Chapter 2: states of the matter (Chapter 2.2), ideal gases (Chapter 2.3.2) and aqueous solutions (Chapter 2.4.3). The gist of environmental chemistry is equilibriums (Chapter 3.2) and chemical reactions (Chapter 3.3). To understand them, the fundamentals of thermodynamics, thermochemistry and reaction kinetics will be presented here.

  3.1 Chemical thermodynamics

  Thermodynamics was originally the study of the energy conversion between heat and mechanical work, but now tends to include macroscopic variables such as temperature, volume, pressure, internal energy and entropy.

  In physics and chemistry, and thereby the environment, thermodynamics includes all processes of equilibrium between water phases, gases and solids. These processes occurring in energetic changes are the key factor for understanding environmental states and thereby environmental changes.

  Changes in heat and kinetic energy can be measured in the work carried out. Specifically, chemical thermodynamics16

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  Physico-Chemical Properties of Nanomaterials

  • Richard C. Pleus, Vladimir Murashov(Authors)
  • 2018(Publication Date)
  • Jenny Stanford Publishing

    (Publisher)

  8 ], Copyright (1998), with permission from Elsevier.

  Chemical characterization is distinct from physicochemical characterization. Physicochemical characterization addresses phenomena that is derived from the physical interactions between chemical constituents and not phenomena that lead to covalent or chemical bonds. Chemical bonds result in a complete change of the electron charge distributions of the participating atoms, resulting in an essential merger of the charge distributions and fields between atoms. This is in contrast to physical bonding, where the charge distributions of participating atoms are merely perturbed. Even though physical interactions are not as transformative as covalent bonding, they can be of similar strength and importantly can manifest themselves collectively and over much longer distances (e.g., several nanometers to centimeters versus angstroms). Physical interactions hold atoms and molecules together in solids and in liquids and in complex phase-segregated systems such as cellular and subcellular biological assemblies. While quantum-mechanical interactions define the nature and temporal charge distributions within a substance through subatomic processes and chemical modifications (i.e., chemical composition), larger-scale physical interactions describe the behavior of those chemical substances and serve as the primary origin of physicochemical properties. Indeed, physical interactions such as those described below are the primary regulating interactions in all environmental safety and health phenomena that do not involve chemical reactions and biological transformations.

  3.3.2    Electrostatic Interactions

  Electrostatic interactions originate from the coulombic force between charges and are pertinent for ions as well as for molecules exhibiting permanent dipoles. A dipole is a separation of positive and negative electrical charges that are inherent within a molecule (or molecular region) that contains no net charge. Molecules like water are polar and exhibit a dipole but do not have a net charge. In contrast, ions (e.g., dissolved chlorine from table salt in water) contain a net charge and sign.

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  Time-Resolved Mass Spectrometry

  From Concept to Applications

  • Pawel L. Urban, Yu-Chie Chen, Yi-Sheng Wang(Authors)
  • 2016(Publication Date)
  • Wiley

    (Publisher)

  Chapter 10 Applications in Fundamental Studies of Physical Chemistry

  10.1 Overview

  A mass spectrometer is a convenient tool for investigating chemical reactions and physical processes in real-time. It provides information-rich output, enabling accurate and precise measurements based on only a small amount of sample. There is no other analytical device offering such advantages simultaneously. For example, optical absorption spectroscopy provides some structural information but requires a large amount of sample, fluorescence spectroscopy is sensitive but is suitable only for fluorescent molecules, and nuclear magnetic resonance spectroscopy provides important structural information but is unsuitable for analyzing small amounts or complex samples. In addition, many spectroscopy techniques are unsuitable for time-resolved analysis since they may not be able to provide sufficient information due to low resolving power and low speeds. Such analytical capabilities are vital for Physical Chemistry studies because reaction kinetics – the core of Physical Chemistry research – concerns variations and changes in molecular quantities and identities in a real-time manner.

  Most Physical Chemistry molecular reactions have distinct temporal properties. These reaction times range from femtoseconds, such as in the case of ultrafast quantum chemical reactions, to seconds, such as in the case of slow chemical equilibria. Quantum chemical reactions typically involve excitation of the internal energy of molecules from the femtosecond to picosecond range via laser excitation or ion–molecule collisions. This excitation induces the transition of a molecule from its original quantum state, normally a lower state (e.g., ground state), to a higher state (e.g., excited state). After excitation, the excess energy will dissipate or relax via various reaction channels. The energy-relaxation time depends on the quantum states involved in the process. For gaseous molecules in the absence of collision, electronic relaxation normally takes few femtoseconds to sub-picoseconds. This relaxation involves the transition of electrons from higher to lower electronic states. Electronically excited molecules typically have lifetimes in the sub-picosecond to low picosecond range, but fluorescent and phosphorescent molecules have longer lifetimes, typically spanning from few nanoseconds to tens of nanoseconds and from few sub-microseconds to minutes, respectively. Intramolecular vibrational relaxation of molecules may range from few sub-picoseconds to sub-nanoseconds, depending on the relaxation process. The selection of suitable time-resolved mass spectrometry (TRMS) approach for the study of certain reactions needs to take into account the spectrum acquisition time (SAT) of the mass spectrometer; the SAT needs to be shorter than duration of the reaction of interest.

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