Energetics

11 Key excerpts on "Energetics"

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  eBook - PDF

  Chemistry, 5th Edition

  • Allan Blackman, Steven E. Bottle, Siegbert Schmid, Mauro Mocerino, Uta Wille(Authors)
  • 2022(Publication Date)
  • Wiley

    (Publisher)

  chemical thermodynamics The study of the role of energy in chemical change and in determining the behaviour of materials. combustion reaction The reaction of a chemical substance with oxygen. endergonic A process for which ΔG is positive. endothermic Describes a change in which energy enters a system from the surroundings. enthalpy (H) The heat content of a system measured under constant pressure conditions. entropy (S) A thermodynamic quantity related to the number of equivalent ways the energy of a system can be distributed. The greater this number, the more probable is the state and the higher is the entropy. exergonic A process in which ΔG is negative. exothermic Describes a change in which energy leaves a system and enters the surroundings. extensive property A property of an object that is described by a physical quantity (such as mass and volume) that is proportional to the size or amount of the object. first law of thermodynamics A formal statement of the law of conservation of energy; ΔU = q + w. Gibbs energy (G) A thermodynamic quantity that relates enthalpy (H), entropy (S) and temperature (T ) by the equation G = H – TS. heat (q) A transfer of energy due to a temperature difference. heat capacity (C) The quantity of heat needed to raise the temperature of an object by 1 K. heat of reaction at constant pressure (q p ) The heat of a reaction in an open system. heat of reaction at constant volume (q v ) The heat of a reaction in a sealed vessel, such as a bomb calorimeter. Hess’s law For any reaction that can be written in steps, the standard enthalpy of reaction is the same as the sum of the standard enthalpies of reaction for the steps. intensive property A property of an object that is described by a physical quantity (such as density and temperature) that is independent of the size of the sample. internal energy (U) The sum of all of the kinetic energies and potential energies of the particles within a system.

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  General Chemistry I as a Second Language

  Mastering the Fundamental Skills

  • David R. Klein(Author)
  • 2015(Publication Date)
  • Wiley

    (Publisher)

  133 CHAPTER 5 ENERGY AND ENTHALPY This chapter is the first part of a much larger topic called thermodynamics. You will revisit thermodynamics in more detail during the second semester of chemistry. The topics in this chapter will lay the foundation that you need for the second semester, so it is important to master the terms, concepts, and problem-solving techniques in this chapter. If you don’t get these topics down now, you will find yourself strug- gling with thermodynamics next semester. In one sentence, thermodynamics is the study of energy and its interconver- sions. Put more simply, thermodynamics is the study of how, why, and when en- ergy can be transferred from one place to another. In this chapter we focus on how energy is transferred. In the second semester of chemistry, you will learn about why and when energy is transferred (entropy and free energy). The first half of this chapter will focus on theory, terminology, and analogies. The second half of the chapter will focus on problem-solving techniques. 5.1 ENERGY We will start off our discussion with the different types of energy, but as we do so, keep in mind that we have still not defined what energy really is. We will get to the definition a bit later. Energy can be classified into the following categories: kinetic energy and po- tential energy. Kinetic energy is energy associated with motion (or velocity), and potential energy is energy associated with position. Let’s start with kinetic energy. When a soccer ball is in motion, it has kinetic energy (you might even remember the term 1 ⁄ 2 mv 2 from your high school physics class). When the soccer ball hits another ball, it will transfer some of its energy to the other ball. Molecules can do the same thing. A molecule in motion has kinetic energy that it can transfer when it collides with another molecule.

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  Medical Biochemistry

  • Gustavo Blanco, Antonio Blanco(Authors)
  • 2017(Publication Date)
  • Academic Press

    (Publisher)

  energy . Chemical transformations are accompanied by energy changes. Understanding these changes is important in biochemistry since it helps to recognize how metabolic processes proceed.

  Thermodynamics is the branch of physics that deals with energy and its transformations. Its basic principles are applicable to biological processes. The fundamental principles of thermodynamics are expressed in the following two laws:

  First law of thermodynamics: The total energy of the universe remains constant (all forms of energy are exchangeable; the energy is neither created nor destroyed).

  Second law of thermodynamics: The entropy of the universe increases constantly (entropy is associated with disorder or randomness).

  Energy

  Commonly, energy is defined as the capacity to produce work. Energy exists in different modes: chemical, thermal, mechanical, electrical, and radiant, all of which can be converted into each other. Energy conversions occur frequently in biological processes. The development and growth of an organism and the continuous renewal of its structures involves a large number of chemical reactions, which are only possible if there is energy input. Similarly, maintenance of body temperature in warm-blooded animals; mechanical work in muscles, cilia, and flagella; generation of electrical impulses in the nervous system; and active transport of substances across membranes are all processes that demand energy.

  The primary source of energy for all forms of life is solar radiation. This is captured and stored as chemical energy by photosynthetic organisms and transferred to other living beings through the feeding chain of biosphere. In aerobic organisms, energy is generated mainly by oxidation of substances incorporated with the food and transferred to compounds that retain it to be used when necessary.

  Chemical energy plays an important role in biological processes. The chemical energy of a compound is represented by the movement and relative position of its atoms and particles and by bonds and attractions between its elements. When a chemical reaction occurs, frequently bonds are broken or formed and the energy content of the molecules changes. The course of a chemical reaction is ultimately determined by the energy content of the system under consideration and the energy exchange between it and the environment.

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  eBook - ePub

  Regents Chemistry--Physical Setting Power Pack Revised Edition

  • Barron's Educational Series, Albert S. Tarendash(Authors)
  • 2021(Publication Date)
  • Barrons Educational Services

    (Publisher)

  Chapter Five

  Energy and chemical reactions

  Key Ideas

  This chapter focuses on the role energy plays in chemical reactions and the factors that determine whether a chemical process will occur under a given set of conditions.

  KEY OBJECTIVES

  At the conclusion of this chapter you will be able to:

  • Define the terms system and surroundings as they relate to chemical processes.
  • Define the terms internal energy and heat.
  • Distinguish between heat and temperature.
  • Distinguish between exothermic and endothermic reactions.
  • Define the term specific heat, and use specific heats to solve calorimetry problems.
  • Relate the first law of thermodynamics to the law of conservation of energy.
  • Define the term heat of reaction, and solve problems involving heats of reaction.
  • Define the terms standard heat of formation and formation reaction, and use the appropriate reference tables to solve problems related to the standard heat of formation.
  • Interpret a potential energy diagram.
  • Define the term activation energy.
  • Define the term spontaneous reaction, and name and describe the factors that drive spontaneous reactions.
  • Define the term entropy, and predict whether a given reaction leads to an increase or a decrease in entropy.

  Passage contains an image

  SECTION I—BASIC (REGENTS-LEVEL) MATERIAL

  NYS REGENTS CONCEPTS AND SKILLS

  Note:

  By the time you have finished Section I, you should have mastered the concepts and skills listed below. The Regents chemistry examination will test your knowledge of these items and your ability to apply them. Concepts are the basic ideas that form the body of the Regents chemistry course (what you need to know!). Skills are the activities that demonstrate your mastery of these concepts (how you show that you know them!). Following each concept or skill is a page reference (given in parentheses) to this chapter.

  5.1

  Concepts: Heat is a transfer of energy (usually thermal energy) from a body of higher temperature to a body of lower temperature. (Page 112

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  Chemistry

  • Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson(Authors)
  • 2015(Publication Date)
  • Openstax

    (Publisher)

  1. US Energy Information Administration, Primary Energy Consumption by Source and Sector, 2012, http://www.eia.gov/totalenergy/data/ monthly/pdf/flow/css_2012_energy.pdf. Data derived from US Energy Information Administration, Monthly Energy Review (January 2014). Chapter 5 | Thermochemistry 227 5.1 Energy Basics By the end of this section, you will be able to: • Define energy, distinguish types of energy, and describe the nature of energy changes that accompany chemical and physical changes • Distinguish the related properties of heat, thermal energy, and temperature • Define and distinguish specific heat and heat capacity, and describe the physical implications of both • Perform calculations involving heat, specific heat, and temperature change Chemical changes and their accompanying changes in energy are important parts of our everyday world (Figure 5.2). The macronutrients in food (proteins, fats, and carbohydrates) undergo metabolic reactions that provide the energy to keep our bodies functioning. We burn a variety of fuels (gasoline, natural gas, coal) to produce energy for transportation, heating, and the generation of electricity. Industrial chemical reactions use enormous amounts of energy to produce raw materials (such as iron and aluminum). Energy is then used to manufacture those raw materials into useful products, such as cars, skyscrapers, and bridges. Figure 5.2 The energy involved in chemical changes is important to our daily lives: (a) A cheeseburger for lunch provides the energy you need to get through the rest of the day; (b) the combustion of gasoline provides the energy that moves your car (and you) between home, work, and school; and (c) coke, a processed form of coal, provides the energy needed to convert iron ore into iron, which is essential for making many of the products we use daily.

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  Biochemistry

  The Chemical Reactions Of Living Cells

  • David Metzler(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  Energetics of Biochemical Reactions We all know from experience the importance of energy to life. We know that we must eat and that hard work not only tires us but makes us hungry. Our bodies generate heat, an observation that led Lavoisier around 1780 to the conclusion that respi-ration represented slow combustion of foods within the body. Later the discovery of the first and second laws of thermodynamics permitted the development of precise, quantitative relationships between heat, energy, and work. Modern bio-chemical literature abounds with references to the thermodynamic quantities energy E, enthalpy H, entropy S, and Gibbs free energy G. The purposes of this chapter are threefold: (1) to provide a short review of thermodynamic equa-tions, (2) to provide tables of thermodynamic quantities for biochemical substances and to ex-plain the use of these data in the consideration of equilibria in biochemical systems, and (3) to in-troduce the adenylate system (consisting of adeno-sine triphosphate, adenosine diphosphate, aden-osine monophosphate, and inorganic phosphate) and its central role in energy metabolism. Some of the many books on thermodynamics available for further study are mentioned in refer-ences 1-5. A. THERMODYNAMICS Thermodynamics 1-5 is concerned with the quan-titative description of heat and energy changes and of chemical equilibria. Knowledge of changes in thermodynamic quantities, such as AH and AS, enables us to predict the equilibrium positions in reactions and whether or not under given circum-stances a reaction will or will not take place. Fur-thermore, the consideration of thermodynamic quantities may provide insight into the nature of forces responsible for bonding between mole-cules. An important restriction in the use of classical thermodynamic information is that it deals only with equilibria and says nothing about kinetics. This has led to the occasional assertion that ther-modynamics is not relevant to biochemistry.

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  Inorganic Chemistry

  An Industrial and Environmental Perspective

  • Thomas W. Swaddle(Author)
  • 1997(Publication Date)
  • Academic Press

    (Publisher)

  Chapter 2 Chemical Energetics 2.1 Kinetics and Thermodynamics THERE ARE two basic questions that a chemist or chemical engineer must ask concerning a given chemical reaction: (a) How far does it go, if it is allowed to proceed to equilibrium? (Indeed, does it go in the direction of interest at all?) (b) How fast does it progress? Question (b) is a matter of chemical kinetics and reduces to the need to know the rate equation and the rate constants (customarily designated k) for the various steps involved in the reaction mechanism. Note that the rate equation for a particular reaction is not necessarily obtainable by inspec- tion of the stoichiometry of the reaction, unless the mechanism is a one-step process--and this is something that usually has to be determined by exper- iment. Chemical reaction time scales range from fractions of a nanosecond to millions of years or more. Thus, even if the answer to question (a) is that the reaction is expected to go to essential completion, the reaction may be so slow as to be totally impractical in engineering terms. A brief review of some basic principles of chemical kinetics is given in Section 2.5. Question (a) is in the province of chemical thermodynamics 1 and amounts to evaluating the equilibrium constant (K). Unlike the rate equa- tion, the equilibrium expression for a typical reaction aA + bB @ cC +dD can be written down by inspection of the stoichiometry: KO= {C}C{D} d {A}a{S} b (2.1) (2.2) 11 12 Chapter 2 Chemical Energetics where the braces represent the activities of the chemical species A, B, C, and D. In simple terms, activity is a thermodynamically effective concen- tration and is related to the stoichiometric concentration (moles per liter of solution, molar, M; or moles per kg of solvent, molal, m) by the activity coefficient 7: {A} = 7[A] (2.3) where the square brackets denote stoichiometric concentration.

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  Biothermodynamics

  Principles and Applications

  • Mustafa Ozilgen, Esra Sorguven Oner(Authors)
  • 2016(Publication Date)
  • CRC Press

    (Publisher)

  1 1 Energy, Entropy, and Thermodynamics 1.1 Energy Energy ( e) is the capacity for doing work. It may exist in a variety of forms and may be transformed from one type to another. Kinetic energy ( e k ) refers to the energy associated with the motion. It is proportional to the square of the system’s velocity. Potential energy ( e p ) refers to the energy that a system has because of its position or configuration. An object may have the capacity for doing work because of its position in a gravitational field (gravitational potential energy), in an electric field (electric potential energy), or in a magnetic field (magnetic potential energy). Internal energy ( u) refers to the energy associated with the chemical structure of the matter. It includes the energy of the translation, rotation, and vibration of the molecules. It is the energy associated with the static constituents of matter like those of the atoms and their chemical bonds. The internal energy of a matter changes with temperature and the pressure acting on the matter. Enthalpy (h) is the energy of a fluid in motion. Consider a fluid particle, which is originally at rest and has an internal energy u. If this fluid particle is set to motion, then its internal energy does not change, but its total energy increases because of the flow motion. The energy that the fluid particle possesses to push all the other fluid particles in front of it is called the flow energy, and it may be estimated as the multiplication of the particles’ pressure and specific volume, pv . The total energy of a flowing fluid particle is then the sum of its internal energy and flow energy. Accordingly, enthalpy is defined as h u pv = + Enthalpy of formation ( Δh f ) is the energy required for the formation of 1 mol of a com- pound from its elements. If all the substances are in their standard conditions, then it is called the standard enthalpy of formation, which is denoted with Dh f O .

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  eBook - ePub

  Chemistry

  With Inorganic Qualitative Analysis

  • Therald Moeller(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  G to equilibrium and electrochemistry is then discussed. Thermodynamic calculations of heats of reactions, equilibrium conditions, phase changes, and rates of reaction at temperatures other than 25°C are demonstrated. The last section applies thermodynamics to a biochemical reaction.

  t hermodynamics (from the Greek “therme” meaning heat or energy, and “dynamis” meaning power ) is the study of the transformation of energy from any one form to another. A complete study of thermodynamics involves such topics as heat, work, changes in state, and chemical energy .

  When applied to chemical systems, thermodynamics serves as a valuable tool in predicting such things as the spontaneity of a chemical reaction, the relationship between the amounts of products and reactants once equilibrium has been established, and the amount of energy absorbed or released during a reaction. However, thermodynamics cannot predict the reaction mechanism nor the reaction rate—these are in the realm of chemical kinetics, which has been explored in

  Chapter 15 .

  In Chapter 5

  we discussed thermochemistry, the branch of thermodynamics that deals with heat in chemical reactions and with ΔH, the change in enthalpy, or heat content, of substances. At this point you may be wondering what more there is to be learned about thermodynamics. From

  Chapter 5 you know that exothermic reactions can be spontaneous and endothermic reactions are not likely to be spontaneous. Isn’t this enough? As you can probably guess, the answer is no. If you go back to Section 5.3 ,

  you will see that there we emphasized the words “often” and “usually” in talking about reaction spontaneity. In this chapter we investigate all of the thermodynamic forces and explain why some changes with positive ΔH are spontaneous, while some changes with negative ΔH are not spontaneous

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  Biomolecules

  From Genes to Proteins

  • Shikha Kaushik, Anju Singh(Authors)
  • 2023(Publication Date)
  • De Gruyter

    (Publisher)

  Now the question arises, how an individual reaction contributes toward specific pathways? A reaction pathway must fulfill two criteria: (i) the individual reactions should be specific, that is, it should give only one particular product (or products), and (ii) the series of reactions that constitute the pathways should be thermodynamically favored. The thermodynamics of metabolic pathways are most readily understood in terms of free energy, and laws of thermodynamics are of utmost importance as they govern the conditions under which a particular reaction will occur or not. These laws are general principles that govern all physical and biochemical processes and make a clear difference between system and surrounding. A system is the quantity of matter present within a defined region, whereas the matter in the rest of the universe constitutes the surrounding.

  The first law of thermodynamics states that the total energy of a system and its surroundings is constant. In other words, energy content of the universe is constant; energy can neither be created nor destroyed. However, energy may be transferred from one form to another. For example, in living systems, chemical energy may be transformed into heat, electrical energy, radiant energy, or mechanical energy.

  Entropy is another important thermodynamic concept and is associated with a state of randomness and disorder of a system. Any change in the randomness is expressed as ΔS, and positive value of ΔS indicates an increase in disorder/randomness. The second law of thermodynamics states that the total entropy of a system and its surrounding always increases for a spontaneous process. J. Willard Gibbs gave the theory of change in energy during a chemical reaction and showed that free energy content, G, of any closed system can be defined as follows:

  G = H − T S

  where H is the enthalpy (heat), S is the entropy, and T is the absolute temperature (in kelvin, K).

  When a chemical reaction takes place at a constant temperature and pressure, the change in free energy (ΔG) of a reacting system is given by the following equation, which combines the two laws of thermodynamics:

  Δ G = Δ H − T Δ S

  where ΔS is the change in entropy, ΔH is the change in enthalpy (heat), and T is the absolute temperature (in K).

  For a reaction to be spontaneous, the free energy change should be negative, and a negative ΔG occurs when the overall entropy of the universe increases. On the other hand, if ΔG is positive, the reaction is nonspontaneous. The system is at equilibrium and no net change takes place when ΔG

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  Aquatic Chemistry

  Chemical Equilibria and Rates in Natural Waters

  • Werner Stumm, James J. Morgan(Authors)
  • 2012(Publication Date)
  • Wiley

    (Publisher)

  2 partial pressure; and so on. Our first step in establishing a framework for such chemical thermodynamic models will be to review some basic principles of thermodynamics. Then we will concentrate on the chemical thermodynamic concepts and tools helpful in setting up and solving models for composition of natural water systems.

  The Four Principles of Thermodynamics

  0. There is an absolute temperature scale, T.

  1. The internal energy, E, is a state function of a system. It is altered by heat transfer to the system, q, and work done by the system, w. Thus dE = dq − dw.

  2. Entropy, S, is a state function of a system. The entropy change of a system is related to the heat transferred by dq/T ≤ dS. If we denote the entropy change of the surroundings of a system by d

  e

  S and the entropy changes interior to the system by d

  i

  S, then dS = d

  e

  S + d

  i

  S is an alternative statement of the second law, wherein d

  i

  S ≥ 0.

  3. The entropy of a body is zero when T is zero.

  The concepts of internal energy and entropy are viewed as “primitive” concepts within thermodynamics, and so the first and second principles of thermodyanmics are primitive, irreducible ideas within thermodynamics. Internal energy and the first law are coupled, as are entropy and the second law. Thus Gibbsian thermodynamics (J. W. Gibbs, 1876) is based on postulation of the internal energy, the temperature, and the entropy, and all else follows from the “primitive” principles and the calculus. The principles of thermodynamics are based on experience and experiments. [Note: It is the province of statistical mechanics to obtain E, V, S as a function of T and P by considering the behavior or molecules in the system (e.g., their translational, vibrational, rotational, and electronic energies). In this context, the notions of work and heat transfer

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