Thermodynamics is the branch of physics which deals with the energy and the work of a system. It is a study of relations between heat, work, temperature, and energy. Sadi Carnot discovered thermodynamics.
There are 4 laws of thermodynamics.
Zeroth law of Thermodynamics
“If two systems are in thermal equilibrium with a third system, then they are in thermal equilibrium with one another”
Thermal equilibrium is the state in which two objects connected by a permeable barrier don't have any heat transfer between them. The Zeroth law states that if the temperature of system 1 is equal to temperature of system 3, and the temperature of system 2 is equal to temperature of system 3; then the temperature of system 1 should be equal to the temperature of system 2. The three systems are said to be in thermal equilibrium with each other.
That is ; If T1 = T3 and T2 = T3, then T1 = T2
First law of Thermodynamics
First law of thermodynamics is thus conventionally stated as: “The change in internal energy of a closed system is equal to the energy added to it in the form of heat (Q) plus the work (W) done on the system by the surroundings.”
Internal energy U of a system or a body with well defined boundaries is the total of the kinetic energy due to the motion of molecules and the potential energy associated with the vibrational motion and electric energy of atoms within molecules.
Second law of Thermodynamics
This law states “The total change in entropy of a system plus its surroundings will always increase for a spontaneous process”.
In statistical mechanics, entropy is a measure of the number of ways a system can be arranged, often taken to be a measure of "disorder" (the higher the entropy, the higher the disorder).
In thermodynamics, a spontaneous process is a process which occurs without any external input to the system.
Third law of Thermodynamics
“The entropy of a perfect crystal of any pure substance approaches zero as the temperature approaches absolute zero.”
![HOW TO ANALAYSE A PERSON, TO IF HE IS GOOD OR BAD. [MY EXPIRENCE]](https://static.wixstatic.com/media/338b83_3327cd5272eb4e17a1de3b1cab48e7a3~mv2.png/v1/fill/w_1024,h_578,fp_0.50_0.50,q_35,blur_30,enc_avif,quality_auto/338b83_3327cd5272eb4e17a1de3b1cab48e7a3~mv2.png)
![HOW TO ANALAYSE A PERSON, TO IF HE IS GOOD OR BAD. [MY EXPIRENCE]](https://static.wixstatic.com/media/338b83_3327cd5272eb4e17a1de3b1cab48e7a3~mv2.png/v1/fill/w_312,h_176,fp_0.50_0.50,q_95,enc_avif,quality_auto/338b83_3327cd5272eb4e17a1de3b1cab48e7a3~mv2.png)
Can we reverse entropy locally (e.g., in refrigerators) without violating the second law?
Is time’s arrow (the flow of time) fundamentally tied to entropy?
Why is it impossible to reach absolute zero in practice?
What happens to atoms and time at absolute zero—does everything truly "stop"?
Could quantum mechanics allow a loophole to reach or go below absolute zero?
Why is the zeroth law foundational for defining temperature?
Can something feel cold and still be in thermal equilibrium with its surroundings?
keywords
State functions
Reversible process
Irreversible process
Enthalpy
Entropy
Gibbs free energy
Carnot cycle
Thermal equilibrium
Transitive property of temperature
Thermometry
Temperature scale
Calibration
Internal energy
Conservation of energy
Heat capacity
Specific heat
Joule’s experiment
Calorimetry
Closed system
Open system
Isothermal process
Adiabatic process
Work done by gas
Entropy
Heat engines
Heat flow
Irreversibility
Spontaneous processes
Carnot efficiency
Thermal efficiency
Clausius statement
Kelvin-Planck statement
Perpetual motion machine (second kind)
Time’s arrow
Absolute zero
Entropy at 0 K
Perfect crystal
Cryogenics
Quantum ground state
Cooling limits
Time’s arrow
Order vs disorder
Universe entropy
Thermodynamic paradoxes
Information theory
Maxwell’s demon
Heat death of the universe
Thermodynamic equilibrium