Fundamentals Of Thermodynamics Chem 223 PDF

Fundamentals of Thermodynamics Chem 223 Dr. Abeer S. Elsherbiny A. S. Elsherbiny 1  Course content Chapter1: Introduction Chapter2: Work, heat and first law of thermodynamics Chapter 3: Second , third law of thermodynamics Chapter4: Thermodynami...

Fundamentals of Thermodynamics Chem 223 Dr. Abeer S. Elsherbiny A. S. Elsherbiny 1  Course content Chapter1: Introduction Chapter2: Work, heat and first law of thermodynamics Chapter 3: Second , third law of thermodynamics Chapter4: Thermodynamics of solutions Chapter 5: Chemical equilibrium A. S. Elsherbiny 2  Marks distribution Activity 25 marks Oral 25 marks Final exam 100 marks A. S. Elsherbiny 3 Chapter 1 Introduction A. S. Elsherbiny 4  Thermodynamics definition Thermodynamics: is the branch of science that deals with the study of different forms of energy and the quantitative relationships between them. Why is the study of Thermodynamics important? 1-The study of thermodynamics is important because many machines and modern devices: change heat into work, such as an automobile engine or turn work into heat or cooling, such as a refrigerator. 2-Understanding how reactions reach equilibrium and what their composition is at equilibrium 5 A. S. Elsherbiny Thermodynamics is a macroscopic science that deals with such properties as pressure, temperature, and volume. Thermodynamics when studied on a macroscopic scale (large scale) is called classical thermodynamics Statistical thermodynamics: studied on a microscopic scale (molecular scale) A. S. Elsherbiny 6  Important definitions in thermodynamics Heat (q) is a transfer of energy as a result of a temperature difference between bodies Energy: is the ability to do work. Work (w): is a transfer of energy that can cause motion against an opposing force. A. S. Elsherbiny 7  Units of heat , energy and work The most common units used are: Joule, calorie Calorie: the amount of heat energy needed to raise the temperature of one gram of water one degree Celsius in temperature. A. S. Elsherbiny 8  The SI unit of energy is the joule (J): The calorie (cal), which was originally defined as the amount of heat required to raise the temperature of 1 gram of water by 1oC, is now defined by: non-SI units A. S. Elsherbiny 9  System and surrounding A system is the portion of the universe being studied, e.g.(Chemical reaction, bacteria, reaction vessel, metabolic Pathway). Surroundings are the rest of the universe that is outside of the system.[ surroundings are everything outside the system] the system is separated from the surroundings by The boundary (system wall) and may be real or imaginary. Changes in a system are associated with the transfer of energy 10 A. S. Elsherbiny Example: 1 mole of oxygen confined in a cylinder fitted with a piston, is a thermodynamic system. ❑ The cylinder and the piston and all other objects outside the cylinder, form the surroundings. ❑ Here the boundary between the system (oxygen) and the surroundings (cylinder and the piston) are clearly defined A. S. Elsherbiny 11  System and surrounding ❖ If energy as heat cannot pass through the system wall, it is termed an adiabatic wall, and the system is said to be thermally isolated or thermally insulated. ❖ If heat can pass through the wall, it is termed a diathermic wall. Like a metal container. ❖ Two systems connected by a diathermic wall are said to be in thermal contact. A. S. Elsherbiny 12  Types of system There are three types of thermodynamic systems, depending on the nature of the boundary 1) An isolated system: cannot transfer matter or energy with its surroundings. The wall of an isolated system must be adiabatic.(e.g. Boiling water in thermos flask) 2) A closed system can exchange energy, but not matter, with its surroundings. The energy exchange may be mechanical (associated with a volume change) or thermal (associated with heat transfer through a diathermic wall). 3) An open system can exchange both matter and energy with its surroundings. 13 A. S. Elsherbiny  Isolated, Closed and Open Systems Isolated Closed Open System System System Neither energy Energy, but not Both energy and nor matter can matter can be matter can be be exchanged. exchanged. exchanged. 14 Isolated, Closed and Open Systems A. S. Elsherbiny 15  Problems 1) Which type of thermodynamic system is an ocean? an aquarium? a pizza delivery bag? a greenhouse? ocean: open, aquarium: closed, a pizza delivery bag: isolated, a greenhouse: closed. A. S. Elsherbiny 16  Problems An isolated system has an initial temperature of 30oC. It is then placed on top of a bunsen burner for an hour. What is the final temperature? The final temperature will be 30oC. Remember, an isolated system does not allow energy transfer. A. S. Elsherbiny 17  A macroscopic system: is a large system containing many atoms or molecules. A microscopic system: is a system consisting of a single atom or molecule. Macroscopic properties: apply only to a macroscopic system and are properties of the whole system. such as temperature, volume, composition, density, viscosity, surface tension, refractive index, color. The study of macroscopic properties involves thermodynamics Microscopic properties: such as kinetic energy and momentum are mechanical in nature. 18 A. S. Elsherbiny  State of System and State Variables When macroscopic properties of a system have definite values, the system is said to be in a definite state Whenever there is a change in any one of the macroscopic properties, the system is said to change into a different state Thus the state of a system is fixed by its macroscopic properties. state variables: when the state of a system changes with the change in any of the macroscopic properties. It follows that when a system changes from one state (initial state) to another state (final state), 19 A. S. Elsherbiny  Thermodynamic Variables Thermodynamic variables are the observable macroscopic variables of a system, such as P, V,T and n. If they are used to describe an equilibrium state of the system, they are known as state variables. Equation of state: is a functional relationship between the state variables; e.g. if P,V and T are the state variables, then the equation of state has the form f(P, V, T) =0. The simpilified equation of state is ideal gas equation PV=nRT 20 A. S. Elsherbiny Two classes for a macroscopic variables: Extensive variables: depends upon the amount of the substances present in the system; e.g. mass, volume, entropy, heat capacity, enthalpy, magnetic moment. Intensive variables: independent on the amount of the substances present in the system; e.g. pressure, temperature, magnetic field, density, viscosity, refractive index, surface tension and specific heat. The quotient of two extensive variables is an intensive variable, such as density and molar volume. Example: 1- Vm = V/n; Vm = molar volume 2- density= mass/volume 21 A. S. Elsherbiny Thermodynamic Equilibrium: Occurs in a system in which the macroscopic properties do not undergo any change with time. The term thermodynamic equilibrium implies the existence of three kinds of equilibria system. These are: (i)Thermal equilibrium: no flow of heat from one position of the system to another. (Temp. is constant) ii) Mechanical equilibrium: no mechanical work is done by one part of the system on another part of the system.(pressure is constant) (iii) Chemical equilibrium: if the composition of the various phases in the system remains the same throughout. A. S. Elsherbiny 22  Process A process refers to the change of a system from one equilibrium state to another. which is usually accompanied by a change in energy or mass. For ex., a temperature difference is the driving force that causes a flow of heat. The initial and final states of a process are its end- points. Process types according to heat trasnsfer -Exothermic process: it is a process that relates heat transfer from system to the surroundings - Endothermic process: it is a process that absorbs heat from the surroundings 23 A. S. Elsherbiny -Different types of processes connecting an initial state, in such changes: An isobaric process is one in which the pressure of the system remains constant i.e. ΔP = 0 An isochoric process is one in which the volume of the system is constant, ΔV= 0. An isothermal process is one in which the temperature of the system is constant ( ΔT = 0, the system is in thermal contact with constant temperature and both exchange heat with the surroundings ). An adiabatic process is one in which no heat enters or leaves the system; i.e. Δq = 0 i.e the system is thermally isolated from the surroundings. 24 A. S. Elsherbiny For example, if heat is evolved in the system, the temperature of the system increases and if heat is absorbed, the temperature decreases. An isentropic process is one in which the entropy is constant. It is a reversible adiabatic process. A. S. Elsherbiny 25 Graphical representation of the process: 26 A. S. Elsherbiny Cyclic process: The process which brings aback a system to its original state after a series of changes is called a cyclic process. Enthaply change, ΔH = 0 Internal energy change, ΔE = 0 Entropy change, ΔS=0 A. S. Elsherbiny 27  Reversible and Irreversible Processes Reversible process A process takes place infinitesimally slowly and its direction at any point can be reversed by an infinitesimally change in the state of the system. Irreversible process: A process goes from the initial state to the final state in a single step and cannot be carried in the reverse order. Note that, most of the processes are irreversible in nature. 28  Reversible and Irreversible Processes For example; Flow of heat from high temperature to low temperature water flowing from –hill expansion of gas from higher to lower pressure, use of cells or batteries directly They are also called spontaneous process A. S. Elsherbiny 29 Differences between Reversible and Irreversible Processes: Reversible Processes Irreversible Processes takes place by infinitesimal process takes place in finite small steps, the process would time take infinite time to occur is in equilibrium state at all is ‘in equilibrium state only at stages of the operation the initial and final stages of the operation. is unreal as it assumes the is real and can be performed presence of frictionless and actually. weightless piston a little bed of nature processes Most of the nature processes is reversible are irreversible non-spontaneous processes spontaneous processes 30 A. S. Elsherbiny