Second Law of Thermodynamics - Introduction

Places limits on the ability to do useful work

From Claussius

Heat can flow spontaneously from a hot object to a cold object but not spontaneously from a cold object to a hot object

Based on entropy (degree of disorder) - introduced also by Claussius

The entropy of an isolated system never decreases. It can only stay the same or increase.

The total entropy of any system plus that of its environment (system is not isolated as above) increases as a result of any natural process.

Natural processes tend to move toward a stae of greater disorder.

Lord Kelvin

The heat engine formulation

It is impossible to convert heat completely into work in a cyclic process

 

Note: A joule of thermal energy is more disordering to a cold object than to a hot object.