The document discusses key concepts in chemical thermodynamics including:
- The first law of thermodynamics states that energy cannot be created or destroyed, only converted from one form to another.
- Spontaneous processes are those that can proceed without outside intervention. Processes that are spontaneous in one direction are nonspontaneous in reverse.
- Entropy is a measure of disorder or randomness. It increases for spontaneous processes according to the second law of thermodynamics.
- The Gibbs free energy, ΔG, can indicate whether processes are spontaneous or at equilibrium based on its sign and value. If ΔG is negative, the forward reaction is spontaneous.
This document discusses key concepts in chemical thermodynamics including the first, second, and third laws of thermodynamics. It describes how energy, entropy, enthalpy, and Gibbs free energy relate to spontaneous processes and equilibrium. Spontaneous processes are irreversible and result in an increase in entropy of the universe according to the second law. The third law states that the entropy of a pure crystalline substance is 0 at absolute zero. Gibbs free energy can be used to predict spontaneity based on its sign and relationship to the reaction quotient and equilibrium constant.
The document discusses key concepts in chemical thermodynamics including:
1) The first law of thermodynamics states that energy cannot be created or destroyed, only converted from one form to another.
2) Spontaneous processes are those that can proceed without outside intervention. Processes that are spontaneous in one direction are nonspontaneous in the reverse direction.
3) Entropy is a measure of the randomness or disorder of a system. It increases for spontaneous processes according to the second law of thermodynamics.
4) The Gibbs free energy, ΔG, can be used to determine whether a process is spontaneous, with a negative ΔG corresponding to a spontaneous process.
The document discusses key concepts in chemical thermodynamics including:
1) The first law of thermodynamics states that energy cannot be created or destroyed, only converted from one form to another.
2) Spontaneous processes are those that can occur without outside intervention, while reversible processes can be undone by exactly reversing changes made to the system.
3) The second law of thermodynamics states that the entropy of the universe increases for spontaneous processes. Entropy is a measure of disorder and generally increases when the number of possible molecular arrangements increases.
This document discusses key concepts from the first, second, and third laws of thermodynamics. It begins by defining spontaneous and reversible processes, explaining that spontaneous processes have a natural direction while reversible processes can return a system to its initial state. It then introduces entropy, describing how it increases for spontaneous processes based on the second law of thermodynamics. The document also discusses entropy at the molecular level and how it relates to temperature, phase changes, and the number of possible microscopic arrangements. Finally, it covers how entropy is used to define free energy and how free energy changes can indicate whether a process is spontaneous.
This document provides an overview of thermochemistry concepts including:
- Energy can be stored as potential or kinetic energy and is transferred between systems as heat or work. Enthalpy accounts for heat and pressure-volume work.
- Chemical or physical processes can be endothermic (absorb energy) or exothermic (release energy) as measured by their change in enthalpy.
- Hess's law allows calculation of enthalpy changes for complex processes using values for simpler steps. Standard enthalpies of formation are defined as the enthalpy change when forming one mole of a substance from its elements.
These slides are based on the notes provided by the K V Sangathan. For the revision of thermodynamics the notes are pretty awseome. I f only want submit the home work they will do so.I am sure they will help.
THANK YOU
Energy and the biological systems are joined together and no biological world is almost impossible without ATP. This study material intends to explore the beauty of ATP to drive different biological processes.
This document discusses key concepts in chemical thermodynamics including the first, second, and third laws of thermodynamics. It describes how energy, entropy, enthalpy, and Gibbs free energy relate to spontaneous processes and equilibrium. Spontaneous processes are irreversible and result in an increase in entropy of the universe according to the second law. The third law states that the entropy of a pure crystalline substance is 0 at absolute zero. Gibbs free energy can be used to predict spontaneity based on its sign and relationship to the reaction quotient and equilibrium constant.
The document discusses key concepts in chemical thermodynamics including:
1) The first law of thermodynamics states that energy cannot be created or destroyed, only converted from one form to another.
2) Spontaneous processes are those that can proceed without outside intervention. Processes that are spontaneous in one direction are nonspontaneous in the reverse direction.
3) Entropy is a measure of the randomness or disorder of a system. It increases for spontaneous processes according to the second law of thermodynamics.
4) The Gibbs free energy, ΔG, can be used to determine whether a process is spontaneous, with a negative ΔG corresponding to a spontaneous process.
The document discusses key concepts in chemical thermodynamics including:
1) The first law of thermodynamics states that energy cannot be created or destroyed, only converted from one form to another.
2) Spontaneous processes are those that can occur without outside intervention, while reversible processes can be undone by exactly reversing changes made to the system.
3) The second law of thermodynamics states that the entropy of the universe increases for spontaneous processes. Entropy is a measure of disorder and generally increases when the number of possible molecular arrangements increases.
This document discusses key concepts from the first, second, and third laws of thermodynamics. It begins by defining spontaneous and reversible processes, explaining that spontaneous processes have a natural direction while reversible processes can return a system to its initial state. It then introduces entropy, describing how it increases for spontaneous processes based on the second law of thermodynamics. The document also discusses entropy at the molecular level and how it relates to temperature, phase changes, and the number of possible microscopic arrangements. Finally, it covers how entropy is used to define free energy and how free energy changes can indicate whether a process is spontaneous.
This document provides an overview of thermochemistry concepts including:
- Energy can be stored as potential or kinetic energy and is transferred between systems as heat or work. Enthalpy accounts for heat and pressure-volume work.
- Chemical or physical processes can be endothermic (absorb energy) or exothermic (release energy) as measured by their change in enthalpy.
- Hess's law allows calculation of enthalpy changes for complex processes using values for simpler steps. Standard enthalpies of formation are defined as the enthalpy change when forming one mole of a substance from its elements.
These slides are based on the notes provided by the K V Sangathan. For the revision of thermodynamics the notes are pretty awseome. I f only want submit the home work they will do so.I am sure they will help.
THANK YOU
Energy and the biological systems are joined together and no biological world is almost impossible without ATP. This study material intends to explore the beauty of ATP to drive different biological processes.
This document provides information on thermodynamics and spontaneity of chemical reactions. It defines key concepts such as the first and second laws of thermodynamics, entropy, free energy, and Gibbs free energy. Equations for calculating entropy, enthalpy, and Gibbs free energy changes in chemical reactions are presented. Examples are provided to demonstrate how to apply these equations and determine if reactions are spontaneous based on the sign and value of their Gibbs free energy changes. The dependence of spontaneity on temperature is also discussed.
Thermodynamics deals with heat, temperature, and their relation to energy and work. It has four main branches: classical thermodynamics studies whole systems, statistical thermodynamics analyzes properties at a molecular level, equilibrium thermodynamics considers approaching equilibrium, and chemical thermodynamics relates heat and work to chemical reactions. The four laws of thermodynamics establish foundational concepts. The first law concerns conservation of energy, the second law involves increasing entropy, and the third law states that entropy approaches zero as temperature approaches absolute zero. Thermodynamic properties like internal energy, enthalpy, and entropy are defined in terms of heat and temperature.
The document provides an overview of key concepts in thermodynamics. It defines thermodynamics as the branch of science dealing with quantitative relationships between heat and other forms of energy. It then discusses important terms, types of systems, thermodynamic properties and processes, laws of thermodynamics, and other concepts such as internal energy, enthalpy, entropy, spontaneous processes, and Gibbs free energy.
The document discusses key concepts in engineering chemistry including:
1) Laws of thermodynamics like entropy change and Gibbs free energy are covered as well as kinetics concepts like activation energy and the Arrhenius equation.
2) Specific topics covered include the three laws of thermodynamics, concepts like enthalpy, heat capacity, and various thermodynamic processes.
3) The Carnot cycle is discussed as a theoretical reversible heat engine cycle used to demonstrate the maximum efficiency possible for a heat engine.
Thermodynamics is the study of energy and its transformations. The first law of thermodynamics states that energy can neither be created nor destroyed. Spontaneous processes are those that occur without outside intervention. The driving force for spontaneity is an increase in entropy of the universe according to the second law of thermodynamics. Free energy (G) determines whether a process is spontaneous based on the enthalpy (H) and entropy (S) at a given temperature. A negative ΔG value indicates a spontaneous process.
1. The document discusses concepts from engineering chemistry including the laws of thermodynamics, kinetics, and related topics.
2. It explains key thermodynamic concepts such as state functions, path functions, the four laws of thermodynamics, entropy, enthalpy, and Gibbs free energy.
3. The document also discusses kinetic concepts such as activation energy, the Arrhenius equation, and enzyme catalysis using the Michaelis-Menten mechanism.
This document discusses the topics of entropy and spontaneity in chemistry. It defines entropy as a measure of disorder or randomness in a system. Reactions that increase disorder have a positive change in entropy. The standard entropy change of a reaction can be calculated from standard entropy values. A spontaneous process is one that can occur without outside intervention. The Gibbs free energy change (ΔG) determines if a reaction is spontaneous - a negative ΔG means the reaction proceeds spontaneously. Temperature can affect spontaneity through the entropy term in the ΔG equation.
This document provides an overview of key concepts in chemical thermodynamics, including:
1. Systems, surroundings, boundaries, open vs closed vs isolated systems, and extensive vs intensive properties are introduced.
2. The three laws of thermodynamics - first law regarding energy conservation, second law regarding entropy, and third law regarding unattainability of zero kelvin - are briefly outlined.
3. Key thermodynamic processes like isothermal, adiabatic, isobaric, and isochoric processes are defined.
4. Important thermodynamic parameters like internal energy, work, heat, and enthalpy are explained. Sign conventions and the mathematical statement of the first law relating these parameters
This document discusses spontaneous processes and the driving forces behind them in thermodynamics. It explains that spontaneous processes are driven by a decrease in enthalpy or an increase in entropy. While enthalpy change alone cannot predict spontaneity, the introduction of entropy and Gibbs free energy allows better determination of spontaneous processes. The document also discusses how temperature, entropy change, and the relationship between Gibbs free energy and equilibrium constant can be used to analyze spontaneity.
The document discusses the first and second laws of thermodynamics. It defines entropy as a measure of disorder in a system and explains that the second law states that entropy always increases for irreversible processes in closed systems. It provides examples of reversible and irreversible processes. Reversible processes can return to their initial state while irreversible processes, like combustion, cannot. The document also discusses how entropy relates to temperature, heat transfer between objects, and the direction of spontaneous processes in thermodynamics.
The document discusses thermochemistry and the following key points:
- Thermochemistry is the study of energy changes in chemical reactions, especially the heat evolved or absorbed.
- Enthalpy (H) is a state function that equals the internal energy (E) plus pressure-volume work (PV) for a chemical reaction. The enthalpy change (ΔH) of a reaction is the heat absorbed or released under constant pressure.
- Hess's law states that the enthalpy change for an overall reaction is equal to the sum of the enthalpy changes for the individual steps of that reaction. This allows for calculation of enthalpy changes from standard enthalpy of formation values.
The document discusses key concepts from chemical thermodynamics including the first and second laws of thermodynamics, spontaneous and irreversible processes, entropy, and entropy on the molecular scale. It explains that entropy is a measure of disorder and randomness in a system and can be calculated using the equation S = k lnW, where W is the number of microstates corresponding to a given macrostate. The second law of thermodynamics states that the entropy of the universe increases for spontaneous processes.
Chapter 17.2 : Driving Force of ReactionsChris Foltz
The document discusses entropy, enthalpy, and free energy and how they relate to the tendency of reactions to occur. It defines entropy as a measure of disorder or randomness in a system. Reactions favor higher entropy states. Enthalpy relates to the energy change of a reaction. Free energy takes into account both entropy and enthalpy changes and can be used to determine if a reaction is spontaneous, with negative free energy change indicating spontaneity. The document provides examples and calculations to illustrate these concepts.
This document discusses bond enthalpy, bond dissociation enthalpy, and Hess's law of constant heat summation. It provides examples of calculating average bond enthalpy using Hess's law. It also covers spontaneous and non-spontaneous processes, entropy, Gibbs free energy, and the three laws of thermodynamics.
Dr. wael elhelece thermodynamics 230chemWael Elhelece
1. The document discusses key concepts in chemical thermodynamics including energy, heat, work, temperature, and the first law of thermodynamics.
2. It defines important terms and units used to describe thermodynamic processes and explains that energy cannot be created or destroyed, only converted from one form to another.
3. The document also covers spontaneous processes and reversible processes, stating that spontaneous processes occur without outside intervention and reversible processes can return a system and its surroundings to their original states through an exact reversal.
This document provides an overview of thermodynamics concepts including:
- Thermodynamics deals with energy changes in physical and chemical processes.
- Heat is a form of energy while temperature is a measure of average heat or thermal energy.
- Processes involve a change in state, such as isothermal, isobaric, adiabatic, and isochoric processes.
- A system exchanges energy but not mass with its surroundings in a closed system. An isolated system exchanges neither energy nor mass.
These slides cover detailed information about laws of thermodynamics.It include 1st law definition and then its limitation and then entropy etc.Once you read this you will get know about detailed concept of thermodynamics and its laws with examples.
Liquefied Natural Gas (LNG) is produced by cooling natural gas into a liquid form at liquefaction plants. It is then stored or transported as a liquid and regasified at regasification plants before being used. Understanding the thermodynamics of LNG plants is important for analyzing and evaluating the processes involved. The document discusses key thermodynamic concepts like the first and second laws of thermodynamics, entropy, enthalpy, latent and sensible heat, and different refrigeration cycles used in LNG plants. It provides explanations of these concepts and their relevance to analyzing energy transfers and processes in LNG plants.
Principle of bioenergetics & photobiology and photosynthesisDr Kirpa Ram Jangra
This document provides an overview of biochemistry topics including bioenergetics, photobiology, photosynthesis, Gibbs free energy, entropy, redox reactions, ATP, and their importance in metabolism. It was written by Dr. Kirpa Ram and covers:
1) Definitions of bioenergetics, Gibbs free energy, entropy, and their equations.
2) The laws of thermodynamics and how Gibbs free energy and entropy relate the first and second laws.
3) Explanations of systems, surroundings, enthalpy, and redox reactions.
4) The structure, functions, and importance of ATP in cellular metabolism and as the "energy currency of the cell."
This document provides information on thermodynamics and spontaneity of chemical reactions. It defines key concepts such as the first and second laws of thermodynamics, entropy, free energy, and Gibbs free energy. Equations for calculating entropy, enthalpy, and Gibbs free energy changes in chemical reactions are presented. Examples are provided to demonstrate how to apply these equations and determine if reactions are spontaneous based on the sign and value of their Gibbs free energy changes. The dependence of spontaneity on temperature is also discussed.
Thermodynamics deals with heat, temperature, and their relation to energy and work. It has four main branches: classical thermodynamics studies whole systems, statistical thermodynamics analyzes properties at a molecular level, equilibrium thermodynamics considers approaching equilibrium, and chemical thermodynamics relates heat and work to chemical reactions. The four laws of thermodynamics establish foundational concepts. The first law concerns conservation of energy, the second law involves increasing entropy, and the third law states that entropy approaches zero as temperature approaches absolute zero. Thermodynamic properties like internal energy, enthalpy, and entropy are defined in terms of heat and temperature.
The document provides an overview of key concepts in thermodynamics. It defines thermodynamics as the branch of science dealing with quantitative relationships between heat and other forms of energy. It then discusses important terms, types of systems, thermodynamic properties and processes, laws of thermodynamics, and other concepts such as internal energy, enthalpy, entropy, spontaneous processes, and Gibbs free energy.
The document discusses key concepts in engineering chemistry including:
1) Laws of thermodynamics like entropy change and Gibbs free energy are covered as well as kinetics concepts like activation energy and the Arrhenius equation.
2) Specific topics covered include the three laws of thermodynamics, concepts like enthalpy, heat capacity, and various thermodynamic processes.
3) The Carnot cycle is discussed as a theoretical reversible heat engine cycle used to demonstrate the maximum efficiency possible for a heat engine.
Thermodynamics is the study of energy and its transformations. The first law of thermodynamics states that energy can neither be created nor destroyed. Spontaneous processes are those that occur without outside intervention. The driving force for spontaneity is an increase in entropy of the universe according to the second law of thermodynamics. Free energy (G) determines whether a process is spontaneous based on the enthalpy (H) and entropy (S) at a given temperature. A negative ΔG value indicates a spontaneous process.
1. The document discusses concepts from engineering chemistry including the laws of thermodynamics, kinetics, and related topics.
2. It explains key thermodynamic concepts such as state functions, path functions, the four laws of thermodynamics, entropy, enthalpy, and Gibbs free energy.
3. The document also discusses kinetic concepts such as activation energy, the Arrhenius equation, and enzyme catalysis using the Michaelis-Menten mechanism.
This document discusses the topics of entropy and spontaneity in chemistry. It defines entropy as a measure of disorder or randomness in a system. Reactions that increase disorder have a positive change in entropy. The standard entropy change of a reaction can be calculated from standard entropy values. A spontaneous process is one that can occur without outside intervention. The Gibbs free energy change (ΔG) determines if a reaction is spontaneous - a negative ΔG means the reaction proceeds spontaneously. Temperature can affect spontaneity through the entropy term in the ΔG equation.
This document provides an overview of key concepts in chemical thermodynamics, including:
1. Systems, surroundings, boundaries, open vs closed vs isolated systems, and extensive vs intensive properties are introduced.
2. The three laws of thermodynamics - first law regarding energy conservation, second law regarding entropy, and third law regarding unattainability of zero kelvin - are briefly outlined.
3. Key thermodynamic processes like isothermal, adiabatic, isobaric, and isochoric processes are defined.
4. Important thermodynamic parameters like internal energy, work, heat, and enthalpy are explained. Sign conventions and the mathematical statement of the first law relating these parameters
This document discusses spontaneous processes and the driving forces behind them in thermodynamics. It explains that spontaneous processes are driven by a decrease in enthalpy or an increase in entropy. While enthalpy change alone cannot predict spontaneity, the introduction of entropy and Gibbs free energy allows better determination of spontaneous processes. The document also discusses how temperature, entropy change, and the relationship between Gibbs free energy and equilibrium constant can be used to analyze spontaneity.
The document discusses the first and second laws of thermodynamics. It defines entropy as a measure of disorder in a system and explains that the second law states that entropy always increases for irreversible processes in closed systems. It provides examples of reversible and irreversible processes. Reversible processes can return to their initial state while irreversible processes, like combustion, cannot. The document also discusses how entropy relates to temperature, heat transfer between objects, and the direction of spontaneous processes in thermodynamics.
The document discusses thermochemistry and the following key points:
- Thermochemistry is the study of energy changes in chemical reactions, especially the heat evolved or absorbed.
- Enthalpy (H) is a state function that equals the internal energy (E) plus pressure-volume work (PV) for a chemical reaction. The enthalpy change (ΔH) of a reaction is the heat absorbed or released under constant pressure.
- Hess's law states that the enthalpy change for an overall reaction is equal to the sum of the enthalpy changes for the individual steps of that reaction. This allows for calculation of enthalpy changes from standard enthalpy of formation values.
The document discusses key concepts from chemical thermodynamics including the first and second laws of thermodynamics, spontaneous and irreversible processes, entropy, and entropy on the molecular scale. It explains that entropy is a measure of disorder and randomness in a system and can be calculated using the equation S = k lnW, where W is the number of microstates corresponding to a given macrostate. The second law of thermodynamics states that the entropy of the universe increases for spontaneous processes.
Chapter 17.2 : Driving Force of ReactionsChris Foltz
The document discusses entropy, enthalpy, and free energy and how they relate to the tendency of reactions to occur. It defines entropy as a measure of disorder or randomness in a system. Reactions favor higher entropy states. Enthalpy relates to the energy change of a reaction. Free energy takes into account both entropy and enthalpy changes and can be used to determine if a reaction is spontaneous, with negative free energy change indicating spontaneity. The document provides examples and calculations to illustrate these concepts.
This document discusses bond enthalpy, bond dissociation enthalpy, and Hess's law of constant heat summation. It provides examples of calculating average bond enthalpy using Hess's law. It also covers spontaneous and non-spontaneous processes, entropy, Gibbs free energy, and the three laws of thermodynamics.
Dr. wael elhelece thermodynamics 230chemWael Elhelece
1. The document discusses key concepts in chemical thermodynamics including energy, heat, work, temperature, and the first law of thermodynamics.
2. It defines important terms and units used to describe thermodynamic processes and explains that energy cannot be created or destroyed, only converted from one form to another.
3. The document also covers spontaneous processes and reversible processes, stating that spontaneous processes occur without outside intervention and reversible processes can return a system and its surroundings to their original states through an exact reversal.
This document provides an overview of thermodynamics concepts including:
- Thermodynamics deals with energy changes in physical and chemical processes.
- Heat is a form of energy while temperature is a measure of average heat or thermal energy.
- Processes involve a change in state, such as isothermal, isobaric, adiabatic, and isochoric processes.
- A system exchanges energy but not mass with its surroundings in a closed system. An isolated system exchanges neither energy nor mass.
These slides cover detailed information about laws of thermodynamics.It include 1st law definition and then its limitation and then entropy etc.Once you read this you will get know about detailed concept of thermodynamics and its laws with examples.
Liquefied Natural Gas (LNG) is produced by cooling natural gas into a liquid form at liquefaction plants. It is then stored or transported as a liquid and regasified at regasification plants before being used. Understanding the thermodynamics of LNG plants is important for analyzing and evaluating the processes involved. The document discusses key thermodynamic concepts like the first and second laws of thermodynamics, entropy, enthalpy, latent and sensible heat, and different refrigeration cycles used in LNG plants. It provides explanations of these concepts and their relevance to analyzing energy transfers and processes in LNG plants.
Principle of bioenergetics & photobiology and photosynthesisDr Kirpa Ram Jangra
This document provides an overview of biochemistry topics including bioenergetics, photobiology, photosynthesis, Gibbs free energy, entropy, redox reactions, ATP, and their importance in metabolism. It was written by Dr. Kirpa Ram and covers:
1) Definitions of bioenergetics, Gibbs free energy, entropy, and their equations.
2) The laws of thermodynamics and how Gibbs free energy and entropy relate the first and second laws.
3) Explanations of systems, surroundings, enthalpy, and redox reactions.
4) The structure, functions, and importance of ATP in cellular metabolism and as the "energy currency of the cell."
Charging Fueling & Infrastructure (CFI) Program by Kevin MillerForth
Kevin Miller, Senior Advisor, Business Models of the Joint Office of Energy and Transportation gave this presentation at the Forth and Electrification Coalition CFI Grant Program - Overview and Technical Assistance webinar on June 12, 2024.
Top-Quality AC Service for Mini Cooper Optimal Cooling PerformanceMotor Haus
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Dahua provides a comprehensive guide on how to install their security camera systems. Learn about the different types of cameras and system components, as well as the installation process.
1. Chemical
Thermodynamics
First Law of Thermodynamics
• You will recall from Chapter 5 that
energy cannot be created nor
destroyed.
• Therefore, the total energy of the
universe is a constant.
• Energy can, however, be converted
from one form to another or transferred
from a system to the surroundings or
vice versa.
2. Chemical
Thermodynamics
Spontaneous Processes
• Spontaneous processes
are those that can
proceed without any
outside intervention.
• The gas in vessel B will
spontaneously effuse into
vessel A, but once the
gas is in both vessels, it
will not spontaneously
4. Chemical
Thermodynamics
Spontaneous Processes
• Processes that are spontaneous at one
temperature may be nonspontaneous at other
temperatures.
• Above 0C it is spontaneous for ice to melt.
• Below 0C the reverse process is spontaneous.
5. Chemical
Thermodynamics
Reversible Processes
In a reversible process
the system changes in
such a way that the
system and
surroundings can be
put back in their original
states by exactly
reversing the process.
Changes are
infinitesimally small in
a reversible process.
7. Chemical
Thermodynamics
Entropy
• Entropy (S) is a term coined by Rudolph
Clausius in the 19th century.
• Clausius was convinced of the
significance of the ratio of heat
delivered and the temperature at which
it is delivered, q
T
10. Chemical
Thermodynamics
Entropy
• For a process occurring at constant
temperature (an isothermal process):
qrev = the heat that is transferred when the
process is carried out reversibly at a constant
temperature.
T = temperature in Kelvin.
11. Chemical
Thermodynamics
Second Law of Thermodynamics
The second law of thermodynamics:
The entropy of the universe does not
change for reversible processes
and
increases for spontaneous processes.
Reversible (ideal):
Irreversible (real, spontaneous):
13. Chemical
Thermodynamics
Second Law of Thermodynamics
The entropy of the universe increases (real,
spontaneous processes).
But, entropy can decrease for individual systems.
Reversible (ideal):
Irreversible (real, spontaneous):
14. Chemical
Thermodynamics
Entropy on the Molecular Scale
• Ludwig Boltzmann described the concept of
entropy on the molecular level.
• Temperature is a measure of the average
kinetic energy of the molecules in a sample.
15. Chemical
Thermodynamics
Entropy on the Molecular Scale
• Molecules exhibit several types of motion:
Translational: Movement of the entire molecule from
one place to another.
Vibrational: Periodic motion of atoms within a molecule.
Rotational: Rotation of the molecule on about an axis or
rotation about bonds.
16. Chemical
Thermodynamics
Entropy on the Molecular Scale
• Boltzmann envisioned the motions of a sample of
molecules at a particular instant in time.
This would be akin to taking a snapshot of all the
molecules.
• He referred to this sampling as a microstate of the
thermodynamic system.
17. Chemical
Thermodynamics
Entropy on the Molecular Scale
• Each thermodynamic state has a specific number of
microstates, W, associated with it.
• Entropy is
S = k lnW
where k is the Boltzmann constant, 1.38 1023 J/K.
18. Chemical
Thermodynamics
Entropy on the Molecular Scale
Implications:
• more particles
-> more states -> more entropy
• higher T
-> more energy states -> more entropy
• less structure (gas vs solid)
-> more states -> more entropy
19. Chemical
Thermodynamics
Entropy on the Molecular Scale
• The number of microstates and,
therefore, the entropy tends to increase
with increases in
Temperature.
Volume (gases).
The number of independently moving
molecules.
21. Chemical
Thermodynamics
Solutions
Dissolution of a solid:
Ions have more entropy
(more states)
But,
Some water molecules
have less entropy
(they are grouped
around ions).
Usually, there is an overall increase in S.
(The exception is very highly charged ions that
make a lot of water molecules align around them.)
22. Chemical
Thermodynamics
Entropy Changes
• In general, entropy
increases when
Gases are formed from
liquids and solids.
Liquids or solutions are
formed from solids.
The number of gas
molecules increases.
The number of moles
increases.
24. Chemical
Thermodynamics
Third Law of Thermodynamics
The entropy of a pure crystalline
substance at absolute zero is 0.
Entropy:
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No stereotypes,
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http://www.garageband.com/artist/entropy_1
28. Chemical
Thermodynamics
Practical uses: surroundings & system
Entropy Changes in Surroundings
• Heat that flows into or out of the system
also changes the entropy of the
surroundings.
• For an isothermal process:
29. Chemical
Thermodynamics
Practical uses: surroundings & system
Entropy Changes in Surroundings
• Heat that flows into or out of the system also changes
the entropy of the surroundings.
• For an isothermal process:
• At constant pressure, qsys is simply
H for the system.
30. Chemical
Thermodynamics
Link S and H: Phase changes
A phase change is isothermal
(no change in T).
Entropy
system
For water:
Hfusion = 6 kJ/mol
Hvap = 41 kJ/mol
If we do this reversibly: Ssurr = –Ssys
31. Chemical
Thermodynamics
Entropy Change in the Universe
• The universe is composed of the system and
the surroundings.
Therefore,
Suniverse = Ssystem + Ssurroundings
• For spontaneous processes
Suniverse > 0
Practical uses: surroundings & system
34. Chemical
Thermodynamics
TSuniverse is defined as the Gibbs free
energy, G.
For spontaneous processes: Suniverse > 0
And therefore: G < 0
Practical uses: surroundings & system
…Gibbs Free Energy
G is easier to determine than Suniverse.
So:
Use G to decide if a process is spontaneous.
35. Chemical
Thermodynamics
Gibbs Free Energy
1. If G is negative, the
forward reaction is
spontaneous.
2. If G is 0, the system
is at equilibrium.
3. If G is positive, the
reaction is spontaneous
in the reverse direction.
36. Chemical
Thermodynamics
Standard Free Energy Changes
Standard free energies of formation, Gf
are analogous to standard enthalpies of
formation, Hf.
G can be looked up in tables,
or
calculated from S° and H.
38. Chemical
Thermodynamics
Free Energy and Temperature
• There are two parts to the free energy
equation:
H— the enthalpy term
TS — the entropy term
• The temperature dependence of free
energy comes from the entropy term.
39. Chemical
Thermodynamics
Free Energy and Temperature
By knowing the sign (+ or -) of S and H,
we can get the sign of G and determine if a
reaction is spontaneous.
40. Chemical
Thermodynamics
Free Energy and Equilibrium
Remember from above:
If G is 0, the system is at equilibrium.
So G must be related to the equilibrium
constant, K (chapter 15). The standard free
energy, G°, is directly linked to Keq by:
41. Chemical
Thermodynamics
Free Energy and Equilibrium
Under non-standard conditions, we need to use
G instead of G°.
Q is the reaction quotiant from chapter 15.
Note: at equilibrium: G = 0.
away from equil, sign of G tells which way rxn goes
spontaneously.
42. Chemical
Thermodynamics
Gibbs Free Energy
1. If G is negative, the
forward reaction is
spontaneous.
2. If G is 0, the system
is at equilibrium.
3. If G is positive, the
reaction is spontaneous
in the reverse direction.