Thermodynamics Class 11 Notes Physics Chapter 12 - CBSE
Chapter : 12
What Are Thermodynamics ?
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Thermodynamics
The study of the flow of mass, heat and energy is the study of thermodynamics.
Thermodynamic Terminology
System
A notable part of the universe that is kept under observation is known as the system.
Surroundings
The remaining part of the universe except for the system which isn’t kept under observation is known as surroundings.
Types Of System
Open System
The system in which heat energy and mass energy both circulate.
Eg: Human body.
Closed System
A system with constant mass that experiences heat energy flow.
Eg: Pressure cooker.
Isolated System
The system where none of the flow takes place.
Eg: Thermoflask.
Thermodynamic Equilibrium
Mechanical Equilibrium
Mechanical equilibrium is brought about by the absence of mechanical motion, constant
pressure, and volume.
Thermal Equilibrium
Thermal equilibrium is created by the constant heat and temperature w.r.t. time.
Chemical Equilibrium
The chemical equilibrium is reached when the rate of forward reaction equals the rate of backward reaction.
Temperature
Temperature is a measure of the average kinetic energy of the particles in an object. When the temperature increases, the motion of these particles also increases. Temperature is measured with a thermometer or a
calorimeter.
Zeroth Law Of Thermodynamics
The zeroth law may be stated as follows: If a body C, be in thermal equilibrium with two other bodies, A and B, then A and B are in thermal equilibrium with one another.
Internal Energy
Internal energy is the totality of the elements of the energy impacted by the system's internal forces. It is frequently represented by the letters U or E.
Modes of Energy Transport
Heat
Heat (Q) is the energy that is transmitted as a result of temperature variations between a system and its surroundings.
Work
Work (W) is the energy expended to overcome the outside forces operating on the system.
Laws Of Thermodynamics
First Law of Thermodynamics
According to the first law of thermodynamics, energy cannot be generated or destroyed.
∆U = Q + W
Second Law Of Thermodynamics
The state of entropy of the entire universe, as an isolated system will always increase over time, is the standard statement of the second law of thermodynamics.
Entropy
The measure of randomness or disorder in the process of a body is known as its entropy. It is a state function and is represented as S.
$$\Delta S =\frac{Q_{rev}}{\text{T}}$$
Boyle’s Law
At constant temperature, the volume of a given mass of gas is inversely proportional to its pressure.
$$\text{V}\propto\frac{1}{\text{P}}$$
Charles’ Law
At constant pressure, the volume of a given mass of a gas is directly proportional to its absolute temperature.
V ∝ T
Gay Lussac’s Law
At constant volume, pressure of a given mass of a gas is directly proportional to the temperature.
P ∝ T
Avogadro’s Law
Avogadro’s law states that equal volumes of all gases under the same conditions of temperature and pressure contain equal number of molecules.
Isothermal Process
The constant temperature process is known as the isothermal process. Here, ∆U=0 and ∆H=0.
$$\text{W} =-2.303n\text{RT}.log\frac{\text{V}_{2}}{\text{V}_{1}}\\\text{Q} = 2.303\text{nRT}.\text{log}\frac{\text{V}_{2}}{\text{V}_{1}}$$
Enthalpy
Enthalpy is the measurement of energy in a thermodynamic system. The quantity of enthalpy equals to the total content of heat of a system, equivalent to addition of the system's internal energy and the product of volume and pressure.
Adiabatic Process
When the heat exchanged with the surrounding is zero, such a process is known as adiabatic process.
TVγ−1 = Constant,
TγP1−γ
Q = 0 ⇒ W = ∆U
∆H = n CP ∆T
Isochoric Process
Constant volume process is known as isochoric process. Here, W = 0, ∆H = nCp ∆T and ∆U = nCv ∆T = Qv
Isobaric Process
Constant pressure process is known as isobaric process. Here, W = −P∆V = −n R∆T
∆H = np ∆T = Qp and ∆U = n CV∆T
Reversible Process
A reversible process is where the participants go back to its initial form by inculcating minor or negligible changes in their surroundings.
Irreversible Process
An irreversible process is a naturally occurring phenomenon, which does not go back to its original state.
