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Questions and Answers
Which of the following is true regarding a thermodynamic process said to be 'reversible'?
Which of the following is true regarding a thermodynamic process said to be 'reversible'?
- The process occurs spontaneously in one direction.
- The process is spontaneous.
- The process involves a significant increase in entropy.
- The process can be turned back such that both the system and surroundings return to their original states, with no other change anywhere else in the universe. (correct)
In an adiabatic process, heat is transferred into or out of the system.
In an adiabatic process, heat is transferred into or out of the system.
False (B)
What is the term for a system in which no matter or energy can be exchanged with the surroundings?
What is the term for a system in which no matter or energy can be exchanged with the surroundings?
isolated system
For a gas expanding into a vacuum, also known as _______ expansion, the work done is zero.
For a gas expanding into a vacuum, also known as _______ expansion, the work done is zero.
Match the following terms with their corresponding descriptions:
Match the following terms with their corresponding descriptions:
Which of the following statements accurately describes the concept of thermal equilibrium?
Which of the following statements accurately describes the concept of thermal equilibrium?
The first law of thermodynamics states that energy can be created or destroyed.
The first law of thermodynamics states that energy can be created or destroyed.
What is the term for the heat content of a system at constant pressure?
What is the term for the heat content of a system at constant pressure?
The heat capacity at constant volume is mathematically expressed as $C_v = \frac{{\partial ______}}{{\partial T}}_V $.
The heat capacity at constant volume is mathematically expressed as $C_v = \frac{{\partial ______}}{{\partial T}}_V $.
Which of the following is an example of an intensive property?
Which of the following is an example of an intensive property?
The value of $'R'$, the ideal gas constant, is the same regardless of the units used for pressure, volume, and temperature.
The value of $'R'$, the ideal gas constant, is the same regardless of the units used for pressure, volume, and temperature.
What is the criteria for two physical systems to be in thermal equilibrium?
What is the criteria for two physical systems to be in thermal equilibrium?
Work is the product of force and ______.
Work is the product of force and ______.
For which type of process is the change in internal energy equal to zero?
For which type of process is the change in internal energy equal to zero?
The heat 'q' is positive when energy is lost by the system.
The heat 'q' is positive when energy is lost by the system.
The molar heat capacity at constant volume ($C_v$) and constant pressure ($C_p$) are related. Which equation properly describes the relationship for an ideal gas?
The molar heat capacity at constant volume ($C_v$) and constant pressure ($C_p$) are related. Which equation properly describes the relationship for an ideal gas?
What is the value of the work done for an adiabatic free expansion?
What is the value of the work done for an adiabatic free expansion?
If the mass of the system is 1 gram then the heat capacity is called ______ heat of the system.
If the mass of the system is 1 gram then the heat capacity is called ______ heat of the system.
What remains constant in an isochoric process?
What remains constant in an isochoric process?
For any process, the change in internal energy (ΔU) is equal to the heat added to the system (q) minus the work done by the system (w); this is expressed: ΔU = q - w
For any process, the change in internal energy (ΔU) is equal to the heat added to the system (q) minus the work done by the system (w); this is expressed: ΔU = q - w
In terms of pressure (P) and volume (V), what is the formula for calculating work done during a reversible process?
In terms of pressure (P) and volume (V), what is the formula for calculating work done during a reversible process?
Which of the following processes is most closely associated with the rapid cooling observed in a carbon dioxide fire extinguisher?
Which of the following processes is most closely associated with the rapid cooling observed in a carbon dioxide fire extinguisher?
The molar heat capacity is termed ______ if we have only one mole of substance.
The molar heat capacity is termed ______ if we have only one mole of substance.
A 'Path function' depends only on the initial and final states of the system, and are independent of the path used to reach from.
A 'Path function' depends only on the initial and final states of the system, and are independent of the path used to reach from.
Based on the text, what equation relates the relationship between state function & an extensive property?
Based on the text, what equation relates the relationship between state function & an extensive property?
Flashcards
Thermodynamics
Thermodynamics
The study of energy transformations involving heat, work, and internal energy.
Isolated System
Isolated System
It cannot exchange matter or energy with its surroundings.
Closed System
Closed System
It can exchange energy but not matter with its surroundings.
Open System
Open System
It can exchange both matter and energy with its surroundings.
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Intensive Properties
Intensive Properties
Properties that do not depend on the amount of matter (e.g., temperature, pressure).
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Extensive Properties
Extensive Properties
Properties that depend on the amount of matter (e.g., mass, volume).
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State Function
State Function
A function whose value depends only on the initial and final states, not the path taken.
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Path Function
Path Function
A function whose value depends on the path taken to reach a particular state.
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Internal Energy (U)
Internal Energy (U)
The sum of kinetic and potential energy of all particles in the system.
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Reversible Process
Reversible Process
A process where the system's state changes, and it can return to its initial state reversing the change.
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Thermal Equilibrium
Thermal Equilibrium
A state where two systems in contact have no net exchange of energy.
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1st Law of Thermodynamics
1st Law of Thermodynamics
Energy is conserved; energy can't be created or destroyed, only converted.
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Enthalpy (H)
Enthalpy (H)
It is the amount of heat content in a system, which changes at a constant pressure.
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Heat Capacity (C)
Heat Capacity (C)
The heat required to raise the temperature of a substance.
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Molar Heat Capacity
Molar Heat Capacity
Heat capacity per mole of substance.
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Isothermal Process
Isothermal Process
A process at constant temperature.
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Adiabatic Process
Adiabatic Process
A process with no heat transfer.
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Isobaric Process
Isobaric Process
A process at constant pressure.
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Isochoric Process
Isochoric Process
A process at constant volume.
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- Engineering Chemistry Module -1 covers the Laws of Thermodynamics and Kinetics according to the Fall Semester 2022-2023 revised syllabus.
Laws of Thermodynamics
- Includes entropy change in selected processes, spontaneity of chemical reactions, Gibbs free energy, and the Carnot cycle.
- Deals with energy, heat, and work, all measured in Joules.
- Work is defined as Force times displacement and also equal to N x m.
Basic Terminology
- Studies Thermodynamic systems and their properties.
- A thermodynamic system is the quantity of matter or region in space under analysis.
- The surroundings include everything external to the system.
- There is an area called the System Boundary, separating the system from the surroundings.
Types of Systems
- Isolated System: No exchange of matter or energy with the surroundings.
- Closed System: Allows energy exchange but not matter exchange with the surroundings.
- Open System: Allows exchange of both matter and energy with the surroundings.
Properties of a System
- Intensive Properties: Do not depend on the amount of matter in a sample (e.g., temperature, boiling point).
- Extensive Properties: Depend on the amount of matter in a sample (e.g., weight, length).
State and Path Functions
- State Function: Depends only on the initial and final states, independent of the path taken (e.g., temperature, pressure, internal energy, enthalpy).
- Path Function: Depends on the path between the initial and final states (e.g., work done, heat).
Internal Energy
- Internal energy (U) comprises kinetic and potential energy.
- Internal energy is a state function and an extensive property of the system.
- Changes in internal energy occur when energy is transferred into or out of the system as heat or work.
- The change in internal energy is expressed as: ΔUsystem = Ufinal state – Uinitial state
System Processes
- Adiabatic: No heat is transferred.
- Isothermal: Constant temperature.
- Isobaric: Constant pressure.
- Isochoric: Constant volume.
System Work
- Work (W) is force (F) times distance (x) moved in the direction of the force.
- Work done (dw) when a system expands by dV against a pressure Pex is: dw = PexdV
- Total work done by the system to expand from volume Vi to Vf is: W = ∫dV
Reversible Process
- A reversible process can return the system and surroundings to their original states with no other change in the universe.
- Achieved by an infinitesimal modification of a variable.
Thermal Equilibrium
- Systems are in thermal equilibrium if there is no net flow of heat between them.
- The 0th Law of Thermodynamics: If two systems are separately in thermal equilibrium with a third, they are also in thermal equilibrium with each other
First Law of Thermodynamics
- The energy of an isolated system remains constant, energy can neither be created nor destroyed.
- Heat (q) and work (w) are equivalent ways of changing a system's internal energy.
- +ve indicates an energy transfer to a system
- -ve indicates a loss of energy from a system
Formula
- Change in internal energy equation is: ΔU = q - w.
Enthalpy
- At constant pressure, enthalpy (H) is defined as H = U + PV.
- Change in enthalpy: ΔU = ΔH - PAV or ΔH = ΔU + PAV.
Heat Capacity
- Heat capacity (C) is the amount of heat (q) needed to raise the temperature of a system by: C = q / (T2 - T1)
- The specific heat of system with a mass of 1g is termed specific heat.
- For 1 mole of substance, heat capacity is termed as ‘molar heat capacity’.
- At constant volume w = 0, therefore, ΔU = Cv= (∂U / ∂T)v.
Molar Heat Capacity
- Molar heat capacity at constant pressure (Cp): (∂U / ∂T)p = q + w.
- For an ideal gas: Cp = (∂H / ∂T)p
- Relationship between Cp and Cv: For an ideal gas, PV = RT, Δ(PV) = R ΔT
- Cp = 3/2 R for monoatomic ideal gas.
- Cp = 5/2 R for monoatomic ideal gas.
Isothermal Process Expansion
- For an ideal gas, p = nRT/V.
Adiabatic Process
- No heat is added or removed from a system.
- The equation is: Cv = (∂U / ∂T)v
- ΔU = q + w
Work
- Varies by system and whether is done by or on the system
Isobaric Process
- System is constant pressure
- The work is zero in an isochoric system.
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