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## Entropy is not conserved

Entropy Unlike energy functions, entropy is not conserved in natural process or in isolated systems. For example, consider heat transfer between two objects with different temperature TI and TII (TI …

## Entropy of reversible and irreversible processes

The total entropy, which is a summation of entropy of the system and entropy of the surrounding, is a determinant for the reversibility. The sign of total entropy determines if …

## Spontaneous process

Does spontaneous process mean the fast process? A spontaneous process is simply a process that occurs without the need for additional energy. It does not mean that the process will …

## Entropy

Entropy is one of the thermodynamic functions that describe the condition of the system. What is entropy? What is the physical meaning of entropy? Entropy is related to degree of …

## Thermodynamic status

There are three thermodynamic status: unstable, stable and metastable. Unstable status will spontaneously change into stable or metastable status. Stable status is in energy minimum or equilibrium state, and will …

## Stability and the 2nd law

This video introduces the second law of thermodynamics, the entropy principle. The second law is concerned with the conversion of heat into work and the quality of energy. The quality …

## The week ahead

Welcome to the Third week of the course. We are going to introduce the second law of thermodynamics. Last week, we overviewed the first law of thermodynamics: the energy principle. …

## Summary of week 2

This week, you have practiced the calculation of energy changes using energy balance equations. Many exercises for the calculation of energy changes upon temperature change are presented. You learend how …

## Equation of state for adiabatic, reversible changes of ideal gases

The equation of state for the ideal gases under adiabatic and reversible volume changes can be formulated in a very special form. The physical variables of ideal gases under adiabatic …

## Equation of state for non-ideal gases

The P-V-T relationship for real gas needs modification of ideal gas laws.  1) Compressibility factor    The compressibility factor Z is a correction term to the ideal gas laws.      PV=ZRT, z …

## Perpetual motion machine of the first kind

Perpetual motion machine of the first kind is a machine that can do work indefinitely without an energy input. From ancient, people has been captivated by this concept. The examples …

## Special topic J-T valve

An adiabatic process is one in which no heat is exchanged with surrounding. A special case is adiabatic flow through a valve. This is when the valve is insulated or …

## Equation of state for ideal gases

The equation of state is the relationship among the physical variables that describe the condition of a material. The equation of state for ideal gases is presented. We can use …

## Example 2: Equation of state for ideal gas

Example : In a gas-spring system An ideal gas is contained in a cylinder. Initially the pressure, volume and temperature were P1, V1, and T1. A spring with a spring …

## Adiabatic flame temperature

What is adiabatic flame temperature? When the chemical reaction is combustion reaction, heat is evolved from the reaction. This heat might be used to raise the temperature of the system …