Thermodynamics
Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of thermodynamics, which provide a quantitative description using measurable macroscopic physical quantities and can be explained in terms of microscopic constituents by statistical mechanics.
Thermodynamics applies to a wide variety of topics in science and engineering, especially physical chemistry, biochemistry, chemical engineering, and mechanical engineering, but also in other complex fields such as meteorology.
Historically, thermodynamics developed out of a desire to increase the efficiency of early steam engines, particularly through the work of French physicist Sadi Carnot in 1824, who believed that engine efficiency could help France win the Napoleonic Wars.
Laws of Thermodynamics
Zeroth Law of Thermodynamics
The Zeroth Law of Thermodynamics is essential for the definition of temperature. It states that if two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other. This law allows the establishment of a temperature scale.
First Law of Thermodynamics
The First Law of Thermodynamics is a formulation of the law of conservation of energy in the context of thermodynamic processes. It asserts that energy can be transferred between systems as heat or work, but it cannot be created or destroyed. This principle is often summarized as "energy is conserved."
Second Law of Thermodynamics
The Second Law of Thermodynamics introduces the concept of entropy and states that in any natural thermodynamic process, the total entropy of a system and its surroundings always increases. This law implies that energy conversions are not 100% efficient and that some energy is always lost as heat.
Third Law of Thermodynamics
The Third Law of Thermodynamics states that as the temperature of a system approaches absolute zero, the entropy of a perfect crystal approaches a constant minimum. This law has profound implications for the behavior of matter at extremely low temperatures.
Key Concepts
Entropy
Entropy is a measure of the disorder or randomness in a system. In thermodynamics, it quantifies the amount of energy in a physical system that is not available to do work. The concept of entropy is central to the Second Law of Thermodynamics and plays a critical role in determining the direction of thermodynamic processes.
Heat
Heat is the thermal energy transferred between systems due to a temperature difference. In thermodynamics, heat is a crucial form of energy transfer and is distinct from work, which involves energy transfer due to force applied over a distance.
Temperature
Temperature is a physical quantity that expresses the subjective perceptions of hot and cold. It is a measure of the average kinetic energy of the particles in a system and is central to the definition of thermal equilibrium.
Applications
Chemical Thermodynamics
Chemical thermodynamics studies the interrelation of heat and work with chemical reactions or physical changes of state within the confines of chemical laws. It is fundamental in predicting the spontaneity of reactions and the equilibrium position.
Black Hole Thermodynamics
Black hole thermodynamics seeks to reconcile the laws of thermodynamics with the existence of black hole event horizons. It combines principles of quantum mechanics and general relativity to understand the thermodynamic behavior of black holes.