Thermodynamics deals with the stability of systems and describes whole systems using quantities like temperature and pressure averaged over large numbers of entities like molecules. The document discusses key concepts in thermodynamics including systems, surroundings, open and closed systems, different types of processes, temperature, pressure, work, and heat. It provides definitions and examples to explain these fundamental thermodynamics concepts.
This document discusses key concepts in thermodynamics including:
1. Thermodynamics deals with the stability of systems and describes overall system properties like temperature and pressure, rather than interactions at the particle level.
2. The four main laws of thermodynamics are universal and apply across all disciplines of science and engineering.
3. Thermodynamics considers how energy in the form of heat or work can be transferred to or from a system, and the different types of processes this can occur under such as isothermal, isobaric, or adiabatic processes.
This document provides an overview of key concepts in thermodynamics. It discusses four main points:
1. Thermodynamics deals with the stability of systems and describes what should happen to a system, but not how long processes may take. Systems can remain in metastable states for long periods of time.
2. Temperature has two important meanings in thermodynamics - it is a measure of average kinetic energy and determines the distribution of particles among energy states.
3. Pressure is defined as force per unit area exerted by a fluid. It is related to momentum transfer while temperature is related to kinetic energy.
4. Work and heat are both ways that energy can be transferred to or from a system
1. Thermodynamics deals with the stability of systems and describes what should happen in terms of equilibrium, but not what will actually happen over time which depends on kinetics.
2. The document discusses key concepts in thermodynamics including open and closed systems, state variables, thermodynamic potentials, and the difference between macroscopic and microscopic variables.
3. Microscopic variables are associated with individual particles and change continuously, while macroscopic variables like temperature and pressure are only defined under equilibrium conditions.
its the ppt about giving basic information about thermodynamic which is part of the chemical engineering. it includes all the laws and other features related thermodynamics like entropy-temperature and pressure and other things
Thermodynamics deals with concepts of heat, temperature, and energy conversion. Thermal equilibrium occurs between substances when there is no further heat transfer between them. Internal energy is the total energy of all atoms and molecules in a substance due to their random motion. Thermodynamic systems are classified as open, closed, or isolated based on heat and matter transfer ability. The first law of thermodynamics relates heat and work through a mathematical equation. Entropy is a measure of disorder or randomness that increases for energy received by a system and decreases for energy given out. The second law of thermodynamics prohibits heat from spontaneously flowing from cold to hot without work.
This document discusses key concepts in chemical thermodynamics including:
- Thermodynamics deals with different forms of energy and quantitative relationships between them. Chemical thermodynamics focuses on chemical changes.
- Systems, surroundings, boundaries, closed/open/isolated systems, and state functions like internal energy are defined.
- The first law of thermodynamics states that energy is conserved and can be transformed between different forms like work and heat but not created or destroyed.
This document provides an overview of the course MCT-114: Fundamentals of Thermal Sciences. The objectives of the course are to provide a solid grounding in engineering thermodynamics and its fundamental concepts. Topics covered include the basic concepts, laws of energy, ideal gas model, entropy, and power/refrigeration cycles. The course also introduces heat transfer concepts. The document outlines the suggested textbooks, course learning objectives, and provides an introduction to thermal-fluid sciences, thermodynamics, heat transfer, and fluid mechanics.
This document discusses key concepts in thermodynamics including:
1. Thermodynamics deals with the stability of systems and describes overall system properties like temperature and pressure, rather than interactions at the particle level.
2. The four main laws of thermodynamics are universal and apply across all disciplines of science and engineering.
3. Thermodynamics considers how energy in the form of heat or work can be transferred to or from a system, and the different types of processes this can occur under such as isothermal, isobaric, or adiabatic processes.
This document provides an overview of key concepts in thermodynamics. It discusses four main points:
1. Thermodynamics deals with the stability of systems and describes what should happen to a system, but not how long processes may take. Systems can remain in metastable states for long periods of time.
2. Temperature has two important meanings in thermodynamics - it is a measure of average kinetic energy and determines the distribution of particles among energy states.
3. Pressure is defined as force per unit area exerted by a fluid. It is related to momentum transfer while temperature is related to kinetic energy.
4. Work and heat are both ways that energy can be transferred to or from a system
1. Thermodynamics deals with the stability of systems and describes what should happen in terms of equilibrium, but not what will actually happen over time which depends on kinetics.
2. The document discusses key concepts in thermodynamics including open and closed systems, state variables, thermodynamic potentials, and the difference between macroscopic and microscopic variables.
3. Microscopic variables are associated with individual particles and change continuously, while macroscopic variables like temperature and pressure are only defined under equilibrium conditions.
its the ppt about giving basic information about thermodynamic which is part of the chemical engineering. it includes all the laws and other features related thermodynamics like entropy-temperature and pressure and other things
Thermodynamics deals with concepts of heat, temperature, and energy conversion. Thermal equilibrium occurs between substances when there is no further heat transfer between them. Internal energy is the total energy of all atoms and molecules in a substance due to their random motion. Thermodynamic systems are classified as open, closed, or isolated based on heat and matter transfer ability. The first law of thermodynamics relates heat and work through a mathematical equation. Entropy is a measure of disorder or randomness that increases for energy received by a system and decreases for energy given out. The second law of thermodynamics prohibits heat from spontaneously flowing from cold to hot without work.
This document discusses key concepts in chemical thermodynamics including:
- Thermodynamics deals with different forms of energy and quantitative relationships between them. Chemical thermodynamics focuses on chemical changes.
- Systems, surroundings, boundaries, closed/open/isolated systems, and state functions like internal energy are defined.
- The first law of thermodynamics states that energy is conserved and can be transformed between different forms like work and heat but not created or destroyed.
This document provides an overview of the course MCT-114: Fundamentals of Thermal Sciences. The objectives of the course are to provide a solid grounding in engineering thermodynamics and its fundamental concepts. Topics covered include the basic concepts, laws of energy, ideal gas model, entropy, and power/refrigeration cycles. The course also introduces heat transfer concepts. The document outlines the suggested textbooks, course learning objectives, and provides an introduction to thermal-fluid sciences, thermodynamics, heat transfer, and fluid mechanics.
This document discusses key concepts in chemical thermodynamics including:
- Thermodynamics deals with different forms of energy and quantitative relationships between them. Chemical thermodynamics focuses on chemical changes.
- Systems, surroundings, boundaries, closed/open/isolated systems, and state functions like internal energy are defined.
- The first law of thermodynamics states that energy is conserved and can be transformed between different forms like work and heat but not created or destroyed.
This document discusses key concepts in chemical thermodynamics including:
- Thermodynamics deals with different forms of energy and quantitative relationships between them. Chemical thermodynamics focuses on chemical changes.
- Systems, surroundings, boundaries, closed/open/isolated systems, and state functions like internal energy are defined.
- The first law of thermodynamics states that energy is conserved and can be converted between different forms like work and heat but not created or destroyed.
This document provides information about a thermodynamics course including:
- Recommended textbooks for the course
- Policies such as prohibiting cell phone disturbances and not accepting late assignments
- How to access the course outline and materials online
- An introduction to concepts in thermodynamics including systems, properties, processes, and the first law of thermodynamics.
Thermodynamics is the branch of physics that deals with heat and other forms of energy. The first law of thermodynamics states that the total energy of a system remains constant, such that any increase in one form of energy (such as heat) results in an equal decrease in another form (such as work). The second law states that heat cannot spontaneously flow from a colder body to a hotter body without an input of work. The third law states that the entropy of a perfect crystal approaches zero as the temperature approaches absolute zero.
Chemical Thermodynamic_Insert Watermark.pdfErwinMapalad
Chemical thermodynamics deals with the quantitative relationships between different forms of energy involved in chemical changes and processes. It studies systems, their states, and how they exchange energy and matter with surroundings. A system exchanges energy as either heat or work with its surroundings. The internal energy of a system depends on its state, and can change through heat or work interactions. The first law of thermodynamics states that the total energy in the universe remains constant, as energy may be converted between different forms but cannot be created or destroyed.
This document provides an introduction to engineering thermodynamics for mechanical engineering students. It defines key concepts like system, state, path, process, equilibrium and introduces the three laws of thermodynamics. The first law is the conservation of energy, the second law is the conservation of entropy, and the zeroth law defines thermal equilibrium. It explains the differences between open, closed and isolated systems and discusses properties of state, intensive and extensive properties. Reversible and irreversible processes are also defined. The goal is to provide students the foundation to analyze thermodynamic processes and devices.
Group E of Sanskar Public School completed a physics project on thermodynamics during the 2018-2019 academic year. The project was led by Sawarni Tiwari and included group members Manjeet Kumar, Shreya Tiwari, Mahwish, and Abhishek Singh. The project covered topics such as the laws of thermodynamics, heat and internal energy, state variables, processes like isothermal and adiabatic processes, and the work done in different processes. The principal and physics teacher certified that the project was the work of Group E and praised their initiative, cooperation, and the quality of their content and analysis.
Group E of Sanskar Public School completed a physics project on thermodynamics during the 2018-2019 academic year. The project was led by Sawarni Tiwari and included group members Manjeet Kumar, Shreya Tiwari, Mahwish, and Abhishek Singh. The project covered various topics in thermodynamics including the zeroth law, different types of processes, and the first and second laws of thermodynamics. The group thanked their teacher and principal for guidance and support in completing the successful project.
This document provides definitions and concepts related to thermodynamics. It defines thermodynamics as the science relating heat, work, and properties of systems. A system is the part of the universe being studied, while the surroundings are what is outside the system boundaries. Systems can be closed, open, or isolated depending on if mass and energy cross the boundaries. Properties, state, path, process, and equilibrium are also defined. Temperature is a measure of how heat transfers between bodies in contact until thermal equilibrium is reached.
This document provides an introduction to an intermediate-level course on thermodynamics and statistical mechanics. It discusses how thermodynamics applies to many-body systems and can explain many everyday phenomena. It notes that while the atomic motions can be described by known physics equations, directly solving these equations for macroscopic systems is impossible due to their enormous complexity and number of particles. Therefore, thermodynamics takes a statistical approach, focusing on average properties rather than individual particle motions.
The document provides an overview of key thermodynamic concepts including:
1) Thermodynamics examines the transfer of heat and work to produce mechanical energy.
2) Precise definitions are needed for concepts like system, state, property, process, and reversible process.
3) Ideal gas behavior is an excellent approximation for many aerospace applications and the ideal gas law relates pressure, volume, temperature and moles of gas.
Thermodynamics deals with energy transfer between systems and states of matter. The first law of thermodynamics states that energy is conserved, while the second law introduces entropy and establishes that the entropy of the universe increases over time. Thermodynamics can determine if a reaction will proceed spontaneously based on the energy change and entropy change between reactants and products. A reaction is spontaneous if the change in internal energy is negative and the change in entropy is positive.
In this PPT have have covered
1. Basic thermodynamics definition
2. Thermodynamics law
3. Properties , cycle, Process
4. Derivation of the Process
5.Formula for the numericals.
This topic is use full for those students who want to study basic thermodynamics as a part of their University syllabus.
Most of the university having basic Mechanical engineering as a subject and in this subject Thermodynamics is a topic so by this PPT our aim is to give presentable knowledge of the subject
Thermodynamics deals with stability of systems and tells us what should happen. It concerns heat, work, temperature, pressure, volume and equilibrium. The laws of thermodynamics relate these macroscopic properties and describe spontaneous processes and the behavior of systems as they approach absolute zero. Thermodynamics considers systems as either open, closed, or isolated and can undergo various processes like isothermal, isobaric, or adiabatic processes between different equilibrium states.
1. The document discusses key concepts in thermodynamics including the first and second laws of thermodynamics. It defines internal energy, heat, work, and important thermodynamic terms.
2. The first law states that energy cannot be created or destroyed, only changed in form. The change in internal energy of a system is equal to heat supplied plus work done.
3. Examples are provided to illustrate thermodynamic concepts including the conversion of potential to kinetic energy for a mass of water falling over a waterfall.
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.
The document discusses key concepts in thermodynamics including:
- Systems can be open, closed, or isolated depending on whether work, heat, and mass cross the boundary.
- A system's state is defined by properties like temperature, pressure, and volume. A process occurs as the system moves between states.
- The first law of thermodynamics concerns the conservation of energy as work and heat are applied to a system. The second law concerns entropy.
- Systems must be in thermal, mechanical, and chemical equilibrium for their properties to be well-defined and for reversible processes to occur. Temperature is a measure of thermal equilibrium.
1. Heat and work are two modes of energy transfer that can change a system's state; equilibrium is required for thermodynamic equations relating properties to be valid.
2. Heat is energy transferred due to temperature differences across boundaries; the amount of heat needed to change states depends on the process path.
3. The Zeroth Law defines temperature as a property such that equal temperatures between objects or systems indicates thermal equilibrium.
Why is it incorrect to say that a system contains heatSolution.pdfsantanadenisesarin13
Why is it incorrect to say that a system contains heat?
Solution
System and heat are two different things. Heat is a type of energy, and system is system. The
system can gain heat, but the heat can\'t gain system.
Heat is a property of system . You cannot \"contain heat\". Heat can be regarded as a sense of
the \"energy levels\" of a system.
Strictly speaking heat is the transfer of energy- the flow due to the temperature difference
between one piece of matter to the other.
That is, if you touch your fingers together, you do not feel heat - but if you touch fire (an
ongoing chemical reaction that evolves heat) you will obviously feel heat.
OR
Heat capacity or thermal capacity, is the measurable physical quantity that characterizes the
amount of heat required to change a substance\'s temperature by a given amount. In the
International System of Units (SI), heat capacity is expressed in units of joule(s) (J) per kelvin
(K)
Before the development of modern thermodynamics, it was thought that heat was a fluid, the so-
called caloric. Bodies were capable of holding a certain amount of this fluid, hence the term heat
capacity, named and first investigated by Joseph Black in the 1750s. Today one instead discusses
the internal energy of a system. This is made up of its microscopic kinetic and potential energy.
Heat is no longer considered a fluid. Rather, it is a transfer of disordered energy at the
microscopic level. Nevertheless, at least in English, the term \"heat capacity\" survives. Some
other languages prefer the term thermal capacity, which is also sometimes used in English
\"In physics and thermodynamics, heat is energy transferred from one body, region, or
thermodynamic system to another due to thermal contact or thermal radiation when the systems
are at different temperatures... Thermal energy is sometimes referred to as heat, although the
strict definition of heat requires it to be in transfer between two systems.\"
The term \"enthalpy\" is \"sometimes described as the heat content of a system under a given
pressure, whereas \"heat\" is defined as thermal energy in transit. For the assumption that a
change of enthalpy H is heat to be valid, no energy exchange with the environment must occur
aside from heat or expansion work. GIVEN THIS RESTRICTION, it can be shown that:
* The enthalpy is the total amount of energy that the system can emit through heat
* Adding or removing energy through heat is the only way to change the enthalpy
* The amount of change in enthalpy is equal to the amount of energy added through heat.\"
\"Thus it is as if enthalpy is nothing more than heat \"stored\" by the system, provided the given
restrictions are adhered to.\"
\"However, heat is not the only way to change enthalpy. Enthalpy also changes when the
pressure of the environment is altered, even if no energy is exchanged as heat. In addition,
enthalpy changes when energy is transferred into or out of the system through a means other than
heat or expansion wor.
Thermodynamics is the study of energy and its transformation. It discusses the relationship between heat, work, and the physical properties of systems. Some applications of thermodynamics include pressure cookers, internal combustion engines, steam plants, refrigeration and air conditioning systems, chemical plants, and jet propulsion. The zeroth law of thermodynamics states that if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. A system can be described either through a macroscopic or microscopic approach. The macroscopic approach considers properties like pressure and temperature without examining molecular-level events, while the microscopic approach considers molecular motion and properties like velocity and kinetic energy.
Discovery of An Apparent Red, High-Velocity Type Ia Supernova at 𝐳 = 2.9 wi...Sérgio Sacani
We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
�
(
�
−
�
)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
�
Ca-rich population. Although such an object is too red for any low-
�
cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
�
) with
Λ
CDM. Therefore unlike low-
�
Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
�
truly diverge from their low-
�
counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
PPT on Alternate Wetting and Drying presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
This document discusses key concepts in chemical thermodynamics including:
- Thermodynamics deals with different forms of energy and quantitative relationships between them. Chemical thermodynamics focuses on chemical changes.
- Systems, surroundings, boundaries, closed/open/isolated systems, and state functions like internal energy are defined.
- The first law of thermodynamics states that energy is conserved and can be transformed between different forms like work and heat but not created or destroyed.
This document discusses key concepts in chemical thermodynamics including:
- Thermodynamics deals with different forms of energy and quantitative relationships between them. Chemical thermodynamics focuses on chemical changes.
- Systems, surroundings, boundaries, closed/open/isolated systems, and state functions like internal energy are defined.
- The first law of thermodynamics states that energy is conserved and can be converted between different forms like work and heat but not created or destroyed.
This document provides information about a thermodynamics course including:
- Recommended textbooks for the course
- Policies such as prohibiting cell phone disturbances and not accepting late assignments
- How to access the course outline and materials online
- An introduction to concepts in thermodynamics including systems, properties, processes, and the first law of thermodynamics.
Thermodynamics is the branch of physics that deals with heat and other forms of energy. The first law of thermodynamics states that the total energy of a system remains constant, such that any increase in one form of energy (such as heat) results in an equal decrease in another form (such as work). The second law states that heat cannot spontaneously flow from a colder body to a hotter body without an input of work. The third law states that the entropy of a perfect crystal approaches zero as the temperature approaches absolute zero.
Chemical Thermodynamic_Insert Watermark.pdfErwinMapalad
Chemical thermodynamics deals with the quantitative relationships between different forms of energy involved in chemical changes and processes. It studies systems, their states, and how they exchange energy and matter with surroundings. A system exchanges energy as either heat or work with its surroundings. The internal energy of a system depends on its state, and can change through heat or work interactions. The first law of thermodynamics states that the total energy in the universe remains constant, as energy may be converted between different forms but cannot be created or destroyed.
This document provides an introduction to engineering thermodynamics for mechanical engineering students. It defines key concepts like system, state, path, process, equilibrium and introduces the three laws of thermodynamics. The first law is the conservation of energy, the second law is the conservation of entropy, and the zeroth law defines thermal equilibrium. It explains the differences between open, closed and isolated systems and discusses properties of state, intensive and extensive properties. Reversible and irreversible processes are also defined. The goal is to provide students the foundation to analyze thermodynamic processes and devices.
Group E of Sanskar Public School completed a physics project on thermodynamics during the 2018-2019 academic year. The project was led by Sawarni Tiwari and included group members Manjeet Kumar, Shreya Tiwari, Mahwish, and Abhishek Singh. The project covered topics such as the laws of thermodynamics, heat and internal energy, state variables, processes like isothermal and adiabatic processes, and the work done in different processes. The principal and physics teacher certified that the project was the work of Group E and praised their initiative, cooperation, and the quality of their content and analysis.
Group E of Sanskar Public School completed a physics project on thermodynamics during the 2018-2019 academic year. The project was led by Sawarni Tiwari and included group members Manjeet Kumar, Shreya Tiwari, Mahwish, and Abhishek Singh. The project covered various topics in thermodynamics including the zeroth law, different types of processes, and the first and second laws of thermodynamics. The group thanked their teacher and principal for guidance and support in completing the successful project.
This document provides definitions and concepts related to thermodynamics. It defines thermodynamics as the science relating heat, work, and properties of systems. A system is the part of the universe being studied, while the surroundings are what is outside the system boundaries. Systems can be closed, open, or isolated depending on if mass and energy cross the boundaries. Properties, state, path, process, and equilibrium are also defined. Temperature is a measure of how heat transfers between bodies in contact until thermal equilibrium is reached.
This document provides an introduction to an intermediate-level course on thermodynamics and statistical mechanics. It discusses how thermodynamics applies to many-body systems and can explain many everyday phenomena. It notes that while the atomic motions can be described by known physics equations, directly solving these equations for macroscopic systems is impossible due to their enormous complexity and number of particles. Therefore, thermodynamics takes a statistical approach, focusing on average properties rather than individual particle motions.
The document provides an overview of key thermodynamic concepts including:
1) Thermodynamics examines the transfer of heat and work to produce mechanical energy.
2) Precise definitions are needed for concepts like system, state, property, process, and reversible process.
3) Ideal gas behavior is an excellent approximation for many aerospace applications and the ideal gas law relates pressure, volume, temperature and moles of gas.
Thermodynamics deals with energy transfer between systems and states of matter. The first law of thermodynamics states that energy is conserved, while the second law introduces entropy and establishes that the entropy of the universe increases over time. Thermodynamics can determine if a reaction will proceed spontaneously based on the energy change and entropy change between reactants and products. A reaction is spontaneous if the change in internal energy is negative and the change in entropy is positive.
In this PPT have have covered
1. Basic thermodynamics definition
2. Thermodynamics law
3. Properties , cycle, Process
4. Derivation of the Process
5.Formula for the numericals.
This topic is use full for those students who want to study basic thermodynamics as a part of their University syllabus.
Most of the university having basic Mechanical engineering as a subject and in this subject Thermodynamics is a topic so by this PPT our aim is to give presentable knowledge of the subject
Thermodynamics deals with stability of systems and tells us what should happen. It concerns heat, work, temperature, pressure, volume and equilibrium. The laws of thermodynamics relate these macroscopic properties and describe spontaneous processes and the behavior of systems as they approach absolute zero. Thermodynamics considers systems as either open, closed, or isolated and can undergo various processes like isothermal, isobaric, or adiabatic processes between different equilibrium states.
1. The document discusses key concepts in thermodynamics including the first and second laws of thermodynamics. It defines internal energy, heat, work, and important thermodynamic terms.
2. The first law states that energy cannot be created or destroyed, only changed in form. The change in internal energy of a system is equal to heat supplied plus work done.
3. Examples are provided to illustrate thermodynamic concepts including the conversion of potential to kinetic energy for a mass of water falling over a waterfall.
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.
The document discusses key concepts in thermodynamics including:
- Systems can be open, closed, or isolated depending on whether work, heat, and mass cross the boundary.
- A system's state is defined by properties like temperature, pressure, and volume. A process occurs as the system moves between states.
- The first law of thermodynamics concerns the conservation of energy as work and heat are applied to a system. The second law concerns entropy.
- Systems must be in thermal, mechanical, and chemical equilibrium for their properties to be well-defined and for reversible processes to occur. Temperature is a measure of thermal equilibrium.
1. Heat and work are two modes of energy transfer that can change a system's state; equilibrium is required for thermodynamic equations relating properties to be valid.
2. Heat is energy transferred due to temperature differences across boundaries; the amount of heat needed to change states depends on the process path.
3. The Zeroth Law defines temperature as a property such that equal temperatures between objects or systems indicates thermal equilibrium.
Why is it incorrect to say that a system contains heatSolution.pdfsantanadenisesarin13
Why is it incorrect to say that a system contains heat?
Solution
System and heat are two different things. Heat is a type of energy, and system is system. The
system can gain heat, but the heat can\'t gain system.
Heat is a property of system . You cannot \"contain heat\". Heat can be regarded as a sense of
the \"energy levels\" of a system.
Strictly speaking heat is the transfer of energy- the flow due to the temperature difference
between one piece of matter to the other.
That is, if you touch your fingers together, you do not feel heat - but if you touch fire (an
ongoing chemical reaction that evolves heat) you will obviously feel heat.
OR
Heat capacity or thermal capacity, is the measurable physical quantity that characterizes the
amount of heat required to change a substance\'s temperature by a given amount. In the
International System of Units (SI), heat capacity is expressed in units of joule(s) (J) per kelvin
(K)
Before the development of modern thermodynamics, it was thought that heat was a fluid, the so-
called caloric. Bodies were capable of holding a certain amount of this fluid, hence the term heat
capacity, named and first investigated by Joseph Black in the 1750s. Today one instead discusses
the internal energy of a system. This is made up of its microscopic kinetic and potential energy.
Heat is no longer considered a fluid. Rather, it is a transfer of disordered energy at the
microscopic level. Nevertheless, at least in English, the term \"heat capacity\" survives. Some
other languages prefer the term thermal capacity, which is also sometimes used in English
\"In physics and thermodynamics, heat is energy transferred from one body, region, or
thermodynamic system to another due to thermal contact or thermal radiation when the systems
are at different temperatures... Thermal energy is sometimes referred to as heat, although the
strict definition of heat requires it to be in transfer between two systems.\"
The term \"enthalpy\" is \"sometimes described as the heat content of a system under a given
pressure, whereas \"heat\" is defined as thermal energy in transit. For the assumption that a
change of enthalpy H is heat to be valid, no energy exchange with the environment must occur
aside from heat or expansion work. GIVEN THIS RESTRICTION, it can be shown that:
* The enthalpy is the total amount of energy that the system can emit through heat
* Adding or removing energy through heat is the only way to change the enthalpy
* The amount of change in enthalpy is equal to the amount of energy added through heat.\"
\"Thus it is as if enthalpy is nothing more than heat \"stored\" by the system, provided the given
restrictions are adhered to.\"
\"However, heat is not the only way to change enthalpy. Enthalpy also changes when the
pressure of the environment is altered, even if no energy is exchanged as heat. In addition,
enthalpy changes when energy is transferred into or out of the system through a means other than
heat or expansion wor.
Thermodynamics is the study of energy and its transformation. It discusses the relationship between heat, work, and the physical properties of systems. Some applications of thermodynamics include pressure cookers, internal combustion engines, steam plants, refrigeration and air conditioning systems, chemical plants, and jet propulsion. The zeroth law of thermodynamics states that if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. A system can be described either through a macroscopic or microscopic approach. The macroscopic approach considers properties like pressure and temperature without examining molecular-level events, while the microscopic approach considers molecular motion and properties like velocity and kinetic energy.
Discovery of An Apparent Red, High-Velocity Type Ia Supernova at 𝐳 = 2.9 wi...Sérgio Sacani
We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
�
(
�
−
�
)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
�
Ca-rich population. Although such an object is too red for any low-
�
cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
�
) with
Λ
CDM. Therefore unlike low-
�
Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
�
truly diverge from their low-
�
counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
PPT on Alternate Wetting and Drying presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
JAMES WEBB STUDY THE MASSIVE BLACK HOLE SEEDSSérgio Sacani
The pathway(s) to seeding the massive black holes (MBHs) that exist at the heart of galaxies in the present and distant Universe remains an unsolved problem. Here we categorise, describe and quantitatively discuss the formation pathways of both light and heavy seeds. We emphasise that the most recent computational models suggest that rather than a bimodal-like mass spectrum between light and heavy seeds with light at one end and heavy at the other that instead a continuum exists. Light seeds being more ubiquitous and the heavier seeds becoming less and less abundant due the rarer environmental conditions required for their formation. We therefore examine the different mechanisms that give rise to different seed mass spectrums. We show how and why the mechanisms that produce the heaviest seeds are also among the rarest events in the Universe and are hence extremely unlikely to be the seeds for the vast majority of the MBH population. We quantify, within the limits of the current large uncertainties in the seeding processes, the expected number densities of the seed mass spectrum. We argue that light seeds must be at least 103 to 105 times more numerous than heavy seeds to explain the MBH population as a whole. Based on our current understanding of the seed population this makes heavy seeds (Mseed > 103 M⊙) a significantly more likely pathway given that heavy seeds have an abundance pattern than is close to and likely in excess of 10−4 compared to light seeds. Finally, we examine the current state-of-the-art in numerical calculations and recent observations and plot a path forward for near-future advances in both domains.
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
Mechanisms and Applications of Antiviral Neutralizing Antibodies - Creative B...Creative-Biolabs
Neutralizing antibodies, pivotal in immune defense, specifically bind and inhibit viral pathogens, thereby playing a crucial role in protecting against and mitigating infectious diseases. In this slide, we will introduce what antibodies and neutralizing antibodies are, the production and regulation of neutralizing antibodies, their mechanisms of action, classification and applications, as well as the challenges they face.
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdfSelcen Ozturkcan
Ozturkcan, S., Berndt, A., & Angelakis, A. (2024). Mending clothing to support sustainable fashion. Presented at the 31st Annual Conference by the Consortium for International Marketing Research (CIMaR), 10-13 Jun 2024, University of Gävle, Sweden.
(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...Scintica Instrumentation
Targeting Hsp90 and its pathogen Orthologs with Tethered Inhibitors as a Diagnostic and Therapeutic Strategy for cancer and infectious diseases with Dr. Timothy Haystead.
Embracing Deep Variability For Reproducibility and Replicability
Abstract: Reproducibility (aka determinism in some cases) constitutes a fundamental aspect in various fields of computer science, such as floating-point computations in numerical analysis and simulation, concurrency models in parallelism, reproducible builds for third parties integration and packaging, and containerization for execution environments. These concepts, while pervasive across diverse concerns, often exhibit intricate inter-dependencies, making it challenging to achieve a comprehensive understanding. In this short and vision paper we delve into the application of software engineering techniques, specifically variability management, to systematically identify and explicit points of variability that may give rise to reproducibility issues (eg language, libraries, compiler, virtual machine, OS, environment variables, etc). The primary objectives are: i) gaining insights into the variability layers and their possible interactions, ii) capturing and documenting configurations for the sake of reproducibility, and iii) exploring diverse configurations to replicate, and hence validate and ensure the robustness of results. By adopting these methodologies, we aim to address the complexities associated with reproducibility and replicability in modern software systems and environments, facilitating a more comprehensive and nuanced perspective on these critical aspects.
https://hal.science/hal-04582287
TOPIC OF DISCUSSION: CENTRIFUGATION SLIDESHARE.pptxshubhijain836
Centrifugation is a powerful technique used in laboratories to separate components of a heterogeneous mixture based on their density. This process utilizes centrifugal force to rapidly spin samples, causing denser particles to migrate outward more quickly than lighter ones. As a result, distinct layers form within the sample tube, allowing for easy isolation and purification of target substances.
SDSS1335+0728: The awakening of a ∼ 106M⊙ black hole⋆Sérgio Sacani
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼ 106M⊙ black hole (BH) that is currently in the process of ‘turning on’. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼ 106M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGNobserved in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour. Key words. galaxies: active– accretion, accretion discs– galaxies: individual: SDSS J133519.91+072807.4
1. Basics of Thermodynamics
Four Laws that Drive the Universe
Peter Atkins*
Oxford University Press, Oxford, 2007
Reading
Some of the material covered here is also covered in the chapter/topic on:
Equilibrium
*It is impossible for me to write better than Atkins- his lucid (& humorous) writing style is truly impressive- paraphrasing may lead to loss of
the beauty of his statements- hence, some parts are quoted directly from his works.
MATERIALS SCIENCE
&
ENGINEERING
Anandh Subramaniam & Kantesh Balani
Materials Science and Engineering (MSE)
Indian Institute of Technology, Kanpur- 208016
Email: anandh@iitk.ac.in, URL: home.iitk.ac.in/~anandh
AN INTRODUCTORY E-BOOK
Part of
http://home.iitk.ac.in/~anandh/E-book.htm
A Learner’s Guide
Physical Chemistry
Ira N Levine
Tata McGraw Hill Education Pvt. Ltd., New York (2002).
2. Thermodynamics deals with stability of systems. It tells us ‘what should happen?’.
‘Will it actually happen(?)’is not the domain of thermodynamics and falls under
the realm of kinetics.
At –5C at 1 atm pressure, ice is more stable then water. Suppose we cool water to
–5C. “Will this water freeze?” (& “how long will it take for it to freeze?”) is (are)
not questions addressed by thermodynamics.
Systems can remain in metastable state for a ‘long-time’.
Window pane glass is metastable– but it may take geological time scales for it
to crystallize!
At room temperature and atmospheric pressure, graphite is more stable then
diamond– but we may not lose the glitter of diamond practically forever!
Thermodynamics versus Kinetics
* The term metastable is defined in the chapter on equilibrium.
3. One branch of knowledge that all engineers and scientists must have a grasp of
(to some extent or the other!) is thermodynamics.
In some sense thermodynamics is perhaps the ‘most abstract subject’ and a
student can often find it very confusing if not ‘motivated’ strongly enough.
Thermodynamics can be considered as a ‘system level’ science- i.e. it deals with
descriptions of the whole system and not with interactions (say) at the level of
individual particles.
I.e. it deals with quantities (like T,P) averaged over a large collection of entities
(like molecules, atoms)*.
This implies that questions like: “What is the temperature or entropy of an
atom?”; do not make sense in the context of thermodynamics (at lease in the usual way!).
TD puts before us some fundamental laws which are universal** in nature (and
hence applicable to fields across disciplines).
Thermodynamics (TD): perhaps the most basic science
* Thermodynamics deals with spatio-temporally averaged quantities.
** They apply to the universe a whole as well! (Though the proof is lacking!).
4. To understand the laws of thermodynamics and how they work, first we need to get the
terminology right. Some of the terms may look familiar (as they are used in everyday
language as well)- but their meanings are more ‘technical’and ‘precise’, when used in TD
and hence we should not use them ‘casually’.
System is region where we focus our attention (Au block in figure).
Surrounding is the rest of the universe (the water bath at constant ‘temperature’).
Universe = System + Surrounding (the part that is within the dotted line box in the figure below)
More practically, we can consider the ‘Surrounding’ as the immediate neighbourhood of the
system (the part of the universe at large, with which the system ‘effectively’ interacts).
In this scheme of things we can visualize: a system, the surrounding and the universe at
large.
Things that matter for the surrounding: (i) T, (ii) P, (iii) ability to: do work, transfer heat,
transfer matter, etc. Parameters for the system: (i) Internal energy, (ii) Enthapy, (iii) T, (iv) P,
(v) mass, etc.
The language of TD
In TD we usually do not worry about
the universe at large!
5. To a thermodynamic system two ‘things’ may be added/removed:
energy (in the form of heat &/or work) matter.
An open system is one to which you can add/remove matter (e.g. a open beaker to which
we can add water). When you add matter- you also end up adding heat (which is contained
in that matter).
A system to which you cannot add matter is called closed.
Though you cannot add/remove matter to a closed system, you can still add/remove heat
(you can cool a closed water bottle in fridge).
A system to which neither matter nor heat can be added/removed is called isolated.
A closed vacuum ‘thermos’ flask can be considered as isolated.
Open, closed and isolated systems
Type of boundary Interactions
Open All interactions possible (Mass, Work, Heat)
Closed Matter cannot enter or leave
Semi-permeable Only certain species can enter or leave
Insulated Heat cannot enter or leave
Rigid Mechanical work cannot be done*
Isolated No interactions are possible**
* By or on the system
** Mass, Heat or Work
Mass
Heat
Work
Interactions possible
6. Matter is easy to understand and includes atoms, ions, electrons, etc.
Energy may be transferred (‘added’) to the system as heat, electromagnetic radiation etc.
In TD the two modes of transfer of energy to the system considered are Heat and Work.
Heat and work are modes of transfer of energy and not ‘energy’ itself.
Once inside the system, the part which came via work and the part which came via
heat, cannot be distinguished*. More sooner on this!
Before the start of the process and after the process is completed, the terms heat and
work are not relevant.
From the above it is clear that, bodies contain internal energy and not heat (nor work!).
Matter when added to a system brings along with it some energy. The ‘energy density’
(energy per unit mass or energy per unit volume) in the incoming matter may be higher or lower than the
matter already present in the system.
* The analogy usually given is that of depositing a cheque versus a draft in a bank. Once credited to an account, cheque and draft have no
meaning. (Also reiterated later).
7. Here is a brief listing of a few kinds of processes, which we will encounter in TD:
Isothermal process → the process takes place at constant temperature
(e.g. freezing of water to ice at –10C)
Isobaric → constant pressure
(e.g. heating of water in open air→ under atmospheric pressure)
Isochoric → constant volume
(e.g. heating of gas in a sealed metal container)
Reversible process → the system is close to equilibrium at all times (and infinitesimal
alteration of the conditions can restore the universe (system + surrounding) to the original
state. (Hence, there are no truly reversible processes in nature).
Cyclic process → the final and initial state are the same. However, q and w need not be
zero.
Adiabatic process → dq is zero during the process (no heat is added/removed to/from the
system)
A combination of the above are also possible: e.g. ‘reversible adiabatic process’.
Processes in TD We will deal with some of them in detail later on
8. Though we all have a feel for temperature (‘like when we are feeling hot’); in the context
of TD temperature is technical term with ‘deep meaning’.
As we know (from a commons sense perspective) that temperature is a measure of the ‘intensity of
heat’. ‘Heat flows’ (energy is transferred as heat) from a body at higher temperature to one at lower
temperature. (Like pressure is a measure of the intensity of ‘force applied by matter’→
matter (for now a fluid) flows from region of higher pressure to lower pressure).
That implies (to reiterate the obvious!) if I connect two bodies (A)-one weighing 100kg at 10C
and the other (B) weighing 1 kg at 500C, then the ‘heat will flow’ from the hotter body to
the colder body (i.e. the weight or volume of the body does not matter).
But, temperature comes in two important ‘technical’ contexts in TD:
1 it is a measure of the average kinetic energy (or velocity) of the constituent entities (say molecules)
2 it is the parameter which determines the distribution of species (say molecules) across
various energy states available.
Temperature
500C
Heat flow
direction
10C
A B
9. Let us consider various energy levels available for molecules in a system to be promoted to.
At low temperatures the lower energy levels are expected to be populated more, as compared to
higher energy levels. As we heat the system, more and more molecules will be promoted to
higher energy levels.
The distribution of molecules across these energy levels is given by:
Temperature as a parameter determining the distribution of species across energy levels
10. Celsius (Farenheit, etc.) are relative scales of temperature and zero of these scales do not have
a fundamental significance. Kelvin scale is a absolute scale.
Zero Kelvin and temperatures below that are not obtainable in the classical sense.
Classically, at 0K a perfect crystalline system has zero entropy (i.e. system attains its minimum
entropy state). However, in some cases there could be some residual entropy due to degeneracy
of states (this requires a statistical view point of entropy).
At 0K the kinetic energy of the system is not zero. There exists some zero point energy.
Few points about temperature scales and their properties
11. Pressure* is force per unit area (usually exerted by a fluid on a wall**).
It is the momentum transferred (say on a flat wall by molecules of a gas) per unit area, per unit time. (In
the case of gas molecules it is the average momentum transferred per unit area per unit time on to the flat wall).
P = momentum transferred/area/time.
Pressure is related to momentum, while temperature is related to kinetic energy.
Pressure
Wall
of
a
container
‘Crude schematic’
of particles
impinging on a
wall.
* ‘Normal’pressure is also referred to as hydrostatic pressure.
** Other agents causing pressure could be radiation, macroscopic objects impinging on a wall, etc.
12. Work (W) in mechanics is displacement (d) against a resisting force (F). W = F d
Work has units of energy (Joule, J).
Work can be expansion work (PV), electrical work, magnetic work etc. (many sets of
stimuli and their responses).
Heat as used in TD is a tricky term (yes, it is a very technical term as used in TD).
The transfer of energy as a result of a temperature difference is called heat.
“In TD heat is NOT an entity or even a form of energy; heat is a mode of transfer of
energy” [1].
“Heat is the transfer of energy by virtue of a temperature difference” [1].
“Heat is the name of a process, not the name of an entity” [1].
“Bodies contain internal energy (U) and not heat” [2].
The ‘flow’ of energy down a temperature gradient can be treated mathematically by
considering heat as a mass-less fluid [1] → this does not make heat a fluid!
Heat and Work
[1] Four Laws that Drive the Universe, Peter Atkins, Oxford University Press, Oxford, 2007. [2] Physical Chemistry, Ira N Levine, Tata McGraw Hill Education Pvt. Ltd., New York (2002).
To give an example (inspired by [1]):
assume that you start a rumour that there is ‘lot of’ gold under the class room floor. This rumour ‘may’ spread when persons talk to each other.
The ‘spread of rumor’ with time may be treated mathematically by equations, which have a form similar to the diffusion equations (or heat
transfer equations). This does not make ‘rumour’a fluid!
Expansion work
13. Work is coordinated flow of matter.
Lowering of a weight can do work
Motion of piston can do work
Flow of electrons in conductor can do work.
Heat involves random motion of matter (or the constituent entities of matter).
Like gas molecules in a gas cylinder
Water molecules in a cup of water
Atoms vibrating in a block of Cu.
Energy may enter the system as heat or work.
Once inside the system:
it does not matter how the energy entered the system* (i.e. work and heat are terms
associated with the surrounding and once inside the system there is no ‘memory’ of how
the input was received and
the energy is stored as potential energy (PE) and kinetic energy (KE).
This energy can be withdrawn as work or heat from the system.
* As Aktins put it: “money may enter a back as cheque or cash but once inside the bank there is no difference”.
14. A reversible process is one where an infinitesimal change in the conditions of the
surroundings leads to a ‘reversal’ of the process. (The system is very close to equilibrium
and infinitesimal changes can restore the system and surroundings to the original state).
If a block of material (at T) is in contact with surrounding at (TT), then ‘heat will flow’
into the surrounding. Now if the temperature of the surrounding is increased to (T+T), then
the direction of heat flow will be reversed.
If a block of material (at 40C) is contact with surrounding at 80C then the ‘heat transfer’
with takes place is not reversible.
Though the above example uses temperature differences to illustrate the point, the situation
with other stimuli like pressure (differences) is also identical.
Consider a piston with gas in it a pressure ‘P’. If the external pressure is (P+P), then the
gas (in the piston) will be compressed (slightly). The reverse process will occur if the
external (surrounding pressure is slightly lower).
Maximum work will be done if the compression (or expansion) is carried out in a reversible
manner.
Reversible process
T
Heat flow
direction
T+T
T
Heat flow
direction
TT
Reversible process
40C
Heat flow
direction
80C
NOT a Reversible process
‘Reversible’ is a technical term (like many others) in the context of TD.
15. Let us keep one example in mind as to how we can (sometimes) construct a ‘reversible’
equivalent to a ‘irreversible’ processes.
Let us consider the example of the freezing of ‘undercooled water’* at –5C (at 1 atm
pressure). This freezing of undercooled water is irreversible (P1 below).
We can visualize this process as taking place in three reversible steps hence making the
entire process reversible (P2 below).
How to visualize a ‘reversible’ equivalent to a ‘irreversible’ processes?
* ‘Undercooled’ implies that the water is held in the liquid state below the bulk freezing point! How is this possible?→ read chapter on phase
transformations
Water at –5C Ice at –5C
Irreversible
Water at –5C
Water at –0C
Reversible
Ice at 0C
Ice at –5C
Heat Cool
P2
P1
16. ‘Ultimately’, all forms of energy will be converted to heat!!
One nice example given by Atkins: consider a current through a heating wire of a resistor.
There is a net flow of electrons down the wire (in the direction of the potential gradient)
i.e. work is being done.
Now the electron collisions with various scattering centres leading to heating of the wire
i.e. work has been converted into heat.
(P+P)
In a closed system (piston in the example figure below), if infinitesimal pressure increase
causes the volume to decrease by V, then the work done on the system is:
The system is close to equilibrium during the whole process
thus making the process reversible.
As V is negative, while the work done is positive (work done on the system is positive,
work done by the system is negative).
If the piston moves outward under influence of P (i.e. ‘P’ and V are in opposite directions,
then work done is negative.
Reversible P-V work on a closed system
reversible
dw PdV
1
2
Note that the ‘P’is the pressure inside the container. For the work to be
done reversibly the pressure outside has to be P+P (~P for now). Since
the piston is moving in a direction opposite to the action of P, the work
done by the surrounding is PV (or the work done by the system is PV,
i.e. negative work is done by the system).
P
17. A property which depends only on the current state of the system (as defined by T, P, V etc.)
is called a state function. This does not depend on the path used to reach a particular state.
Analogy: one is climbing a hill- the potential energy of the person is measured by the
height of his CG from ‘say’ the ground level. If the person is at a height of ‘h’ (at point P),
then his potential energy will be mgh, irrespective of the path used by the person to reach
the height (paths C1 & C2 will give the same increase in potential energy of mgh- in figure
below).
In TD this state function is the internal energy (U or E). (Every state of the system can be ascribed to a unique U).
Hence, the work needed to move a system from a state of lower internal energy (=UL) to a
state of higher internal energy (UH) is (UH) (UL). W = (UH) (UL)
The internal energy of an isolated system (which exchages neither heat nor mass) is
constant this is one formulation of the first law of TD.
A process for which the final and initial states are same is called a cyclic process. For a
cyclic process change in a state function is zero.
E.g. U(cyclic process) = 0.
State functions in TD
18. A spontaneous process is one which occurs ‘naturally’, ‘down-hill’ in energy*. I.e. the
process does not require input of work in any form to take place.
Melting of ice at 50C is a spontaneous process.
A driven process is one which wherein an external agent takes the system uphill in energy
(usually by doing work on the system).
Freezing of water at 50C is a driven process (you need a refrigerator, wherein electric
current does work on the system).
Later on we will note that the entropy of the universe will increase during a spontaneous
change. (I.e. entropy can be used as a single parameter for characterizing spontaneity).
Spontaneous and Driven processes
Spontaneous process
(Click to see)
* The kind of ‘energy’we are talking about depends on the conditions. As in the topic on
Equilibrium, at constant temperature and pressure the relevant TD energy is Gibbs free
energy.
19. Heat capacity is the amount of heat (measured in Joules or Calories) needed to raise an
unit amount of substance (measured in grams or moles) by an unit in temperature
(measured in C or K). As mentioned before bodies (systems) contain internal energy and not heat.
This ‘heating’ (addition of energy) can be carried out at constant volume or constant
pressure. At constant pressure, some of the heat supplied goes into doing work of
expansion and less is available with the system (to raise it temperature).
Heat capacity at constant Volume (CV):
It is the slope of the plot of internal energy with temperature.
Heat capacity at constant Pressure (CP):
It is the slope of the plot of enthalpy with temperature.
Units: Joules/Kelvin/mole, J/K/mole, J/C/mole, J/C/g.
Heat capacity is an extensive property (depends on ‘amount of matter’)
If a substance has higher heat capacity, then more heat has to be added to raise its
temperature. Water with a high heat capacity (of CP = 4186 J/K/mole =1 Cal/C/Kg) heats
up slowly as compared to air (with a heat capacity, CP = 29.07J/K/mole) this implies that
oceans will heat up slowly as compared to the atomosphere.
As T0K, the heat capacity tends to zero. I.e near 0 Kelvin very little heat is required to
raise the temperature of a sample. (This automatically implies that very little heat has to
added to raise the temperature of a material close to 0K.
This is of course bad news for cooling to very low temperatures small leakages of heat will lead to drastic increase in temperature).
Heat Capacity
V
V
E
C
T
P
P
H
C
T
20. The internal energy of an isolated system is constant. A closed system may exchange energy
as heat or work. Let us consider a close system at rest without external fields.
There exists a state function U such that for any process in a closed system:
U = q + w [1] (For an infinitesimal change: dU = (U2 U1) = q + w)
q → heat flow into the system
w, W → work done on the system (work done by the system is negative of above- this is just ‘one’ sign convention)
U is the internal energy. Being a state function for a process U depends only of the final
and initial state of the system. U = Ufinal – Uinitial. Hence, for an infinitesimal process it can be written as dU.
In contrast to U, q & w are NOT state functions (i.e. depend on the path followed).
q and w have to be evaluated based on a path dependent integral.
For an infinitesimal process eq. [1] can be written as: dU = q + w
The change in U of the surrounding will be opposite in sign, such that:
Usystem + Usurrounding = 0
Actually, it should be E above and not U {however, in many cases K and V are zero (e.g.
a system at rest considered above) and the above is valid- as discussed elsewhere}.
It is to be noted that in ‘w’ work done by one part of the system on another part is not included.
The Laws of Thermodynamics The First Law
* Depending on the sign convention used there are other ways of writing the first law:
dU = q W, dU = q + W
21. It is impossible to build a cyclic machine* that converts heat into work with 100%
efficiency Kelvin’s statement of the second law.
Another way of viewing the same:
it is impossible to construct a cyclic machine** that completely (with 100% efficiency)
converts heat, which is energy of random molecular motion, to mechanical work, which is
ordered motion.
The unavailable work is due to the role of Entropy in the process.
The Second Law
Heat reservoir Cyclic engine
Heat q
Work (w)
100%
Not possible
Heat reservoir Cyclic engine
Heat q
Work (w)
Cold Reservoir
Heat q’
Kelvin’s
statement of the
second law
The second law comes in many equivalent forms
* For now we are ‘building’‘conceptual machines’!
** These ‘engines’ which use heat and try to produce work are called heat engines.
Called the sink
Possible
Called the source G
T S
H
22. Hot body
Cold body
Heat does not ‘flow*’ from a colder body to a hotter body, without an concomitant change
outside of the two bodies Clausius’s statement of the second law.(a)
This automatically implies that the spontaneous direction of the ‘flow of heat*’ is from a
hotter body to a colder body.(b)
The Kelvin’s and Clausius’s statements of the second law are equivalent. I.e. if we violate
Kelvin’s statement, then we will automatically violate the Clausius’s statement of the
second law (and vice-versa).
Another statement of the second law → the Clausius statement
* Used here in the ‘common usage sense’.
(b) is obvious, but not (a) → though they represent the same fact.
Not possible
Hot body
Cold body
Spontaneous flow not possible
Work
G
T S
H
23. The entropy* of a closed system will increase during any spontaneous change/process.
If we consider the Universe to be a closed system (without proof!!)**, then,
the entropy of the universe will increase during any spontaneous change (process).
A combined (Kelvin + Clausius) statement of the II Law
* Soon we will get down to this mysterious quantity.
** For all we know the Universe could be ‘leaky’ with wormholes to other parallel Universes!
You may want to jump to chapter on
equilibrium to know about Entropy first
Entropy sets the direction for the arrow of time !
24. The efficiency of a heat engine is the amount of work output divided by the amount of heat
input.
This efficiency depends only on the ratio of the temperature of the sink to the temperature
of the source. The maximum efficiency achievable is given by the formula below.
This is surprising as:
there is no mention of the medium of the system (or its properties),
the formula has only temperatures and
the temperature of the sink seems to play a major role (as the presence of the sink is
usually not intentional or obvious→ in a steam engine sink is the air around the engine and
source is the hot steam).
Important message Sink (characterized by its temperature) is as important as the source.
To increase the maximum possible efficiency of a heat engine, either the temperature of the
source has to be increased on the temperature of the sink has to be decreased.
output
heat engine
input
w
q
max sink
source
1
heat engine
T
T
The efficiency of a heat engine
Nicolas Léonard Sadi Carnot in 1824.
“Reflections on the Motive Power of Fire”,
Chapman & Hall ltd, London, 1897.
25. Heat cannot spontaneously flow from a cold (low temperature) body to a hot body.
To make heat flow from a cold body to a hot body, there must be accompanying change
elsewhere (work has to be done to achieve this).
Clausius statement of the second law
26. Heat reservoir
Heat q
Work (w)
Cold Reservoir
Heat q’
Sink
Source
Q & A What is the difference between ‘heat engine’ and ‘work engine’?
Actually both the engines we are going to describe here are usually known as heat engines.
We are differentiating two types of engines to see which one produces work and which one
actually transfers heat.
In the heat engine as the temperature of the cold body tends to zero Kelvin, more and more
work has to be done to transfer the heat from the cold body to the hot body.
Cyclic engine
‘Work engine’
Hot body
Heat q
Work (w)
Cold Body
Heat q’
Cyclic engine
‘heat engine’
The main objective here
is to produce work
The main objective here is
to transfer heat from a
cold body to a hot body
Like a steam engine Like a refrigerator
27. For substances in internal equilibrium, undergoing an isothermal process, the entropy
change goes to zero as T (in K) goes to zero.
The Third Law
0
lim 0
T
S
The law is valid for pure substances and mixtures.
Close to Zero Kelvin, the molecular motions have to be treated using quantum mechanics
→ still it is found that quantum ideal gases obey the third law.
Phenomenological description of the third law.
There does not exist any finite sequence of cyclical process, which can cool a body to zero
Kelvin (absolute zero).
Other statements of the third law.
For a closed system in thermodynamic equilibrium, the entropy of the system approaches a
constant value as the temperature goes to absolute zero.
If there is a unique ground state with minimum energy at zero Kelvin, then the entropy at
zero Kelvin is ZERO. However, if there is a degeneracy with respect to the number of
microstates at absolute zero, then there will be some Residual Entropy.
28. To understand the basics often we rely on simple ‘test-bed’ systems.
In TD one such system is the ideal gas. In an ideal gas the molecules do not interact with
each other (Noble gases come close to this at normal temperatures).
An ideal gas obeys the equation of state:
As the molecules of a ideal gas do not interact with each other, the internal energy of the
system is expected to be ‘NOT dependent’ on the volume of the system.
I.e.:
A gas which obeys both the above equations is called a perfect gas.
Internal energy (a state function) is normally a function of T & V: U = U(T,V).
For a perfect gas: U = U(T) only.
Ideal and Perfect Gases
PV nRT
0
T
U
V
29. The first law says: “you cannot win”.
The second law says: “you can at best break even- that too at zero Kelvin”.
Third law says: “zero Kelvin is unattainable”.
Humorous look at
the three laws
Q & A What is the difference in the ‘status’ of quantities like T, U, S, H, A & G?
T, U & S are fundamental quantities of thermodynamics.
H, A & G do not give us new fundamental concepts, but are for better ‘accounting’ in
thermodynamics.
30. When we mix two (or for that matter more) elements (A & B), the stable phase will be that
with the lowest G. There are three options here (as we have seen in Chapter 4a):
1 Phase separation → A & B do not want to talk to each other
2 Formation of solid solution → A & B do not care about their environment
3 Compound formation → A & B prefer each other’s environment as compared to their own environment
In a compound the each one of the components are fixed to their sub-lattices and hence the
configurational entropy of the compound is zero. This is true in the case of a complete phase
separation as well (i.e. the configurational entropy is zero).
The solid solution is also called a disordered solid solution, in which case each component
is randomly occupies a lattice point without any preference. In practice, there might be
some tendency for ‘ordering’ (i.e. compound formation) or ‘clustering’ (phase separation)
and in that case the ‘random configuration’ assumption will be violated.
What happens when we mix two elements (say Ag and Au→ two crystals*)?
* For the case of Au and Ag, solid solution will form (irrespective of the amount of Au or Ag).
+
1 Phase separation
2 Formation of solid solution
3 Compound formation
=
31. The Gibbs free energy change on mixing (for now we visualize mixing– soon we will see if they actually mix!) is:
Gmix = (Gmixed state – Gunmixed state) = Hmix – T Smix. Hmix = (Hmixed state – Hunmixed)
Hence, if we know two numbers (Hmix, Smix) our job is done!
The game-plan is to find these numbers (especially, Hmix).
Various models are used for this purpose and that can be quite confusing!
Each one of these models come with their own baggage of assumptions (& hence approximations).
The simplest model of mixing is the formation of the ideal solution. In an ideal solution A-
B bonds are energetically no different from the A-A or B-B bonds.
This implies that (Hmix)ideal solution = 0.
If (Hmix)ideal solution 0, which is usually found in practice (i.e. usually the mixing process is
endothermic or exothermic), then we need a more ‘realistic’ computation of Hmix. One of
the popular models is the regular solution model (which is based on the quasi-chemical
approach).
In real alloys the following factors come into the picture, which can lead to substantial
deviation from the some of the models considered: (i) ordering (if Hmix is very negative),
(ii) clustering (leading to deviation from the random configuration model, (iii) strain in the
lattice due to size difference between the atoms (the quasi-chemical model will
underestimate the change in internal energy on mixing), (iv) substantial size difference
leading to the formation of a interstitial solid solution.
32. Ideal solution
.
mix mix
ideal solution
G T S
( ln ln )
mix A A B B
S R X X X X
( ln ln )
mix A A B B
ideal solution
G RT X X X X
A
Increasing T
B
G
mix
→
XB →
0
In an ideal solution: (Hmix)ideal solution = 0
Hence
Click here to see derivation
33. The regular solution model makes the following assumptions:
(i) the enthalpy of mixing is only due to nearest neighbour atoms,
(ii) volume of A and B (per mole) is the same and there is no volume change due to the
mixing process (interatomic distances and bond energies are independent of the
composition),
(iii) point (ii) above also implies that there is no strain in the lattice.
Regular solution model (quasi-chemical approach)
A B AB
+ =
If no. of A-A bonds (per mole) is NAA, the no. of B-B bonds is NBB and the no. of A-B bonds is
NAB and the corresponding bond energies (per bond) are given by EAA, EBB & EAB the internal
energy of the solution is given by (Esolution):
No change in volume
before and after mixing
solution AA AA BB BB AB AB
E N E N E N E
The change in internal energy on mixing (noting that since there is no change in volume, E =
H): mix AB
H N E
1
2 ( )
AB AA BB
E E E E
Where
E < 0 → Hmix negative
Sign of E E = 0 → Hmix is zero
AB bonds are preferred over AA or BB bonds
Ideal solution (no difference between AA, AB or BB bonds
E > 0 → Hmix is positive AB bonds less preferred over AA or BB bonds
Three scenarios are possible regarding the sign of E
34. The equation in the case of the ideal solution for NAB can still be used as
an approximation
E= 0 → Hmix is zero Ideal solution (no difference between AA, AB or BB bonds
For an ideal solution it can be shown that: 0
AB A B
N z N X X
N0 → Avogadro’s No.
z → No. of bonds per atom
E is not too negative or E is not too positive
Let us consider the scenarios a little further
If
If
0
AB A B
N z N X X
0
mix A B A B
H z N X X E X X
This implies: mix A B
H X X
0
z N E
( ln ln )
mix mix
mix A B A A B B
regular solution
H T S
G X X RT X X X X
1
2 ( )
AB AA BB
E E E E
This implies that for regular solutions is the key parameter determining the behaviour of the
regular solution ( in turn depends on E, which is ‘some’ measure of the relative values of AA
and AB bond energies).
We can further consider the liquid and solid phases to be two regular solutions with it own ‘
parameter’: S & L.
35. The effect of (& T)
High T
Low T
< 0 > 0
We will
understand
these figures
in the
coming
slides
Could be –T or ‘nothing’
Could be H, S or G
36. Understanding the G- composition curves: General aspects
is obviously zero for
pure (unmixed) components
As mixing leads to an increase in
entropy and T is always positive
(in K) –TSmix term is always
negative
The Smix term only depends on
the composition for a random
solid solution
The parameter determines
the sign of the Hmix
The Gmix is determined just by the
addition of the Hmix & –TSmix for
each composition
37. < 0
High T
Low T
As Hmix & –TSmix are both
negative Gmix is always negative.
Gmix gets more negative with
increasing T due to the –TSmix.
Hsolution < Hpure components
38. High T
Low T
> 0
Hsolution > Hpure components
Hmix and –TSmix oppose each
other at high ‘enough’ T, –TSmix
wins at all compositions and Gmix
is always negative
At ‘low’ T, Hmix wins over –TSmix
for some compositions (in the
‘middle’) and Gmix turns positive for
this range of compositions.
Except at absolute zero (T), Gmix
always decreases on the addition of a
small amount of solute (even if Hmix
gets ‘very’ positive).
The phase diagram of such a system will show
complete solubility at high T and phase
separation for a range of compositions (in the
middle) at low T.
39. For the case where > 0 (Hmix > 0), why does mixing occur?
Funda Check
In the regular solution model if > 0, then (Hmix > 0). This implies that A atoms prefers A
neighbours and B atoms prefer B neighbours and this should lead to phase separation purele
based on enthalpy considerations. However, at constant T & P it is G which determines the
‘energetics’ (stability) of the system and the term TS is negative for the mixing process.
At ‘high enough’ temperatures, this TS offsets the Hmix term and Gmix is negative (i.e.
the mixed state is energetically preferred).
40. How to understand the case where > 0 (Hmix > 0), at ‘low T’?
Funda Check
In this case for a range of compositions
Gmix is positive. If we plot the G-XB
curves, we observe two points of inflection.
All compositions between that labelled XM
& XN in the G-XB plot will decompose to
phases with compositions XM and XN.
X1 and X2 are determined by the common
tangent construction.
As we shall see in the chapter on phase
transformations, that the transformation
(splitting into two phases) can occur by a
spinodal mechanism or a nucleation and
growth mechanism.
The locus of the points like XM & XN at
various temperatures will give us a region
of phase separation (miscibility gap) in the
phase diagram (the binodal curve). The
locus of the points like XP & XQ will give
us the spinodal curve.
Common tangent to the G-XB curve
We will learn about many of the
concepts in this page in later chapters
41. So far what we have seen is the change in the quantities (H, S, G) on mixing.
To obtain the molar free energy (G per mole) of an ‘alloy’ of a certain composition, we have
to add the linear composition dependent term to the Gmix.
The molar free energy of the system before mixing (Gunmix) is a linear combination of that of
the pure elements (GA and GB).
The Molar Free Energy
mix unmix mix
G G G
unmix A A B B
G X G X G
42. Statistical Thermodynamics
Some ‘thingamajigs’ we will encounter:
Statistical Physics
Macrostate
Microstate
Quantum mechanical picture of a microstate
Statistical physics view of temperature
The equilibrium state
The steady state
The Postulates of statistical thermodynamics
The equal probability postulate
The ergodic* hypothesis
Ensemble, average over ensembles
* Etymology. [Ergon (Greek) = Work] + [Hodos (Greek) = Way] = [Ergoden (German)] + [ic (English)] = [Ergodic] a dynamical systems
term
Clearly we are not going to do much justice to the subject here just a
spattering!
43. Statistical Thermodynamics
Equilibrium statistical mechanics is also referred to as statistical thermodynamics[1].
This branch of science pertains to systems in thermodynamic equilibrium.
The thermodynamic state also known as the macrostate of a system can be
described/fixed by macroscopic parameters like P, T, V & ni (sufficient number of these).
In contrast, the quantum state of the system (or the microstate) requires a large a
large number of variables to describe.
Given that system consists of a large number of particles*, it requires a large
number of variables to describe the microstate [if ‘j’ is the microstate then the wave
function (j) will be a function of a large number of spatial and spin coordinates].
In special cases, wherein the particles do not interact with each other, like the
molecules in a ideal monoatomic gas; it would suffice to specify the quantum states
available to each particle.
Classically a microstate can be described by giving the positions and velocities of
all molecules.
The macrostate is experimentally accessible (observable), while the microstates are
usually not (at least not easily!).
[1] Founding fathers of the field include: J.C. Maxwell, L.E. Boltzmamm, J.W. Gibbs, A. Einstein.
* Defined soon.
44. At the heart of statistical thermodynamics are the concept of an ensemble and couple of
postulates.
In the macroscopic description of a system we carry out spatio-temporal averaging of
quantities. Pressure for instance is obtained by averaging the momentum transferred per unit
area per unit time by the molecules (1023 impacts occur per cm2 per second at 25C and 1
atm pressure). Instead of time averaging, we typically use the concept of a ensemble and the
postulate:
the measured time average of a macroscopic property in a system is equal to the average
value of the property in the ensemble.
An ensemble is a collection of a ‘infinite’ number of isolated systems, which are in the same
macrostate as the system under consideration.
Another way of looking at this is to consider an infinite system. What happens at different
times in a portion of this system, already exists in elsewhere in the infinite system. So
instead of time averaging, we can average over these spatially separated identical systems (in
terms of their macrostate).
45. A system typically consists of a large number (~mole) of entities (atoms, molecules, ions,..)
sometimes refereed to as ‘particles’.
This implies that the system is associated with a large number of degrees of freedom (DoF)
(microscopically). These DoF correspond to the translations, rotations, etc. of the particles.
This ‘implies’ that there are a large number of microstates corresponding to a single
macrostate (i.e. there is a degeneracy with respect to the microstates).
The macrostate, unlike the microstates, can be described with a few variables (P, T, ni, ...).
The Ergodic theorem (a.k.a Gibbs postulate or second postulate of statistical
thermodynamics) says that the macroscopic properties of a system can be found as
probability weighed average of the values for microstates.
In this scenario the internal energy (U) is given as:
Statistical Thermodynamics A brief overview... especially with respect to Entropy
i i
i
U p
pi → probability of microstate ‘i’.
i → energy of the ith microstate.
i → summation is over the ‘i’ microstates.
This simplifies the matters as now we need to know only the probability of finding the ‘ith’
microstate, along with it energy (instead of all the degrees of freedom of the particles).
46. Depending on the conditions we consider various kinds of ensembles.
NVT Cannonical ensemble
NVE Micro-cannonical ensemble
VT Grand-cannonical ensemble
NPT No special name
NPH No special name
The concept of the ensemble and types of ensembles
47. The probability of a microstate as a function of its energy can be computed using the
Boltzmann distribution.
i
i
kT
i kT
i
e
p
e
T → in Kelvin
k → Boltzmann constant (kB)
This can be combined with the Gibbs Entropy equation to compute the Entropy:
ln
i i
i
S k p p
Hence, if we know the probability distributions of the microstates,
we can calculate the entropy of the system.
Now, let us consider as system with constant volume and number of particles. Further, if a
given macrostate corresponds to microstates of equal energy, then we can invoke the Laplace
principle to assume that the all the microstates are equally probable. The Laplace principle is
also knows as the principle of equal a priori probabilities or the first postulate of statistical
thermodynamics.
If is the total number of microstates, then the probability of occurrence of a given
microstate (the ith state) is: (1/).
Substituting into the Gibbs Entropy Equation and summing over all the number of states:
1 1
1 1 1 1
ln ln ln ln
i i
i i
S k p p k k k
1/
i
p
ln
S k
48. This is the Boltzmann equation or the Boltzmann-Planck equation:
ln
S k
ln
S k
Often written with ‘small Omega’or
‘w’instead of the ‘capital Omega’.
(or ) is the number of microstates available to the system. Currently, we are not asking
questions like “will all these microstates will actually be explored by the system?” or “how
long will it take to explore all these microstates?”.
The system may have multiple macrostates and the entropy of the Mth macrostate is
computed using the number of microstates corresponding to that macrostate.
ln
M M
S k
The number of microstates includes both ‘disordered’ and ‘ordered’ microstates. Since the
number of ‘disordered’ microstates >> number of ‘ordered’ microstates. Hence, logarithm of
the number of microstates can be approximated to the logarithm of the number of
‘disordered’ microstates.
ln ln
ordered disordered disordered
S k k
ln
S k w
49. The ‘classically’ defined entropy (macroscopic interpretation) is zero at zero Kelvin.
In the statistical picture of entropy, there could exist a multiplicity of microstates even at zero
Kelvin. These degeneracy/multiplicity of states gives rise to configurational entropy even at
zero Kelvin.
Let us consider an example. Argon crystal at 0K versus CO crystal at 0K. Unlike the Ar
crystal, the linear CO molecule has two orientations (CO or CO). In a CO crystal (at 0K)
if the up and down states are randomly positions on the lattice, this will give rise to
configurational entropy. This will be the residual entropy of CO at RT. This is assuming that
the ordered and disordered states have the same energy.
The microstates for entropy at +ve Kelvin temperatures are given by the Maxwell-Boltzmann
statistics, while residual entropy is described by Normal distribution.
Residual Entropy