Chapter 26 -Laws of thermodynamics

Do you want to understand thermodynamics concepts clearly with real-life examples? Read on…. 

The topics covered in this course are:

1) FIRST Law of Thermodynamics (learn about it’s drawbacks . This led to scientists making the Second Law)

2) Work Done by a Gas

3) Isobaric , Isothermal and Adiabatic expansion : equation derivation

4) Petrol /Gasolene based Internal Combustion engine (passenger car) – Ignition happens due to spark under high pressure

5) Diesel engine (passenger car) – Ignition happens due to Very High pressure (compression)

6) The SECOND Law of Thermodynamics, and concept of Entropy

a) The shortcoming of the FIRST Law

b) Reversible and Irreversible processes

c) As a consequence, came the Second Law of Thermodynamics

7) GIBBS Free Energy — concept , equation and solved problem

8) HELMHOLTZ  Free Energy – concept , equation and solved problem

9) Carnot’s Theorem, Carnot engine, Efficiency derivation

10) Solved Problems

Image shows a Piston and Cylinder arrangement. a GAS inside a closed system.

Thermal energy is applied to the gas , this increases its Kinetic Energy and hence temperature due to internal collisions. OR Thermal energy can be taken away from the gas to cool it, i.e reduce its temperature.

(“HEAT” is a layman terminology actually. Alays say Thermal Energy as far as possible ).

Piston expands and does mechanical WORK when the gas expands due to thermal energy applied to it. The gas pressure decreases.

When the piston connected to a crankshaft comes around and moves to the left in a cyclical way, the gas gets compressed. Its pressure increases. It releases Thermal energy.

Thermodynamics is the interplay of these things – Thermal energy, Work Done, Temperature, Pressure.

Image below: ICE MELTING at room temperature changes its state from solid to liquid water. Then the liquid water further changes its state to gaseous, i.e. water vapour.

The right statement is : “Thermal Energy is transferred from ambient surroundings to the ice block, causing a phase change”.

Another important aspect of Thermodynamics is the DIRECTION of thermodynamic processes.

Heat Energy in layman terms,  Thermal Energy is a more accurate terminology) will always and only flow from Hot Body (higher temperature) to a Colder Body (Lower temperature) , NEVER the other way round from Colder Body to Hotter body (higher temperature).

This concept is obeyed throughout the Universe, not only on Earth. This is critical to understand ENTROPY and the 2nd law of Thermodynamics

Thus, Thermodynamics becomes fundamental to the working of our entire Universe, not only for the Earth.

Some of the well known natural processes of thermodynamics are given below, only for us appreciate the vastness of this subject :

• The thermal energy of the sun’s nuclear fusion and fission beaming down on the earth’s surface
• the rise in temperature of the earth’s surface and the oceans
• the rising hot air currents
• the blowing of the breeze , various winds across seas and continents
• the phenomenon of Tornadoes, Cyclones, Typhoons due to hot rising air currents, in some cases whirlpool formation
• Rigth at the other end, the extremely hot temperatues inside the earth’s crust, where even iron is in molten form, leading to molten lava coming out in Volcanic eruptions ……

Above image shows MASS as well as HEAT ENERGY coming out of a volcano.

THERMAL ENERGY TRANSFER TO THE AIR FROM THE OCEAN AND RAINS

Near the oceans, the air currents circulate constantly. Warm air rises up from the hotter ground. This forms rain clouds along with ater vapur rising from the sea. This forms rain clouds which later give us precious rain.

Meanwhile, the cold air from other neighbouring regions flows into the space vacated by the hot air . The thermodynamic cycle continues for centuries.

image courtesy ,  read more at: https://manoa.hawaii.edu/exploringourfluidearth/physical/atmospheric-effects/wind-formation

It’s amazing that Thermodynamics is always present in NATURE , and in the entire Universe. It does’nt stop, it is constantly happening everywhere , even as we speak…….

The topics covered in this course are:

1) First Law of Thermodynamics (drawbacks leading to the Second Law)

2) Work Done by a Gas

3) Isobaric , Isothermal and Adiabatic expansion : equation derivation

4) Petrol /Gasolene based Internal Combustion engine (passenger car) – a look

5) Diesel engine (passenger car) – a look

6) Entropy – The shortcoming of 1st Law, Irreversible processes, and the Second Law of Thermodynamics

7) HELMHOLTZ FREE ENERGY – concept and equation

8) Carnot’s Thoerem, Carnot engine, Efficiency derivation

9) Solved Problems