Thermodynamics
Otto von Guericke built the world's first vacuum pump in 1650. He demonstrated a vacuum using his Magdeburg hemispheres to disprove Aristotle's supposition that nature abhors a vacuum. Robert Boyle and Robert Hooke built an air pump in 1656 based on Guericke's designs. They noticed a correlation between pressure, temperature, and volume. Denis Papin built a steam digester in 1679. This closed vessel confined steam until high pressure was generated. A steam release valve kept the machine from exploding. Thomas Savery built the first engine in 1697. Thomas Newcomen followed with another design in 1712. These early engines were crude and inefficient. Professor Joseph Black developed fundamental concepts of heat capacity at the University of Glasgow. James Watt worked as an instrument maker there. Black and Watt performed experiments together. Watt conceived the idea of the external condenser. This resulted in a large increase in steam engine efficiency. Sadi Carnot published Reflections on the Motive Power of Fire in 1824. The book outlined basic energetic relations between the Carnot engine and motive power. It marked the start of thermodynamics as a modern science.
Rudolf Clausius restated Carnot's principle known as the Carnot cycle in 1850. His paper On the Moving Force of Heat first stated the second law of thermodynamics. He introduced the concept of entropy in 1865. The zeroth law states that if two systems are each in thermal equilibrium with a third, they are also in thermal equilibrium with each other. Systems are said to be in equilibrium if small random exchanges do not lead to a net change in energy. The first law states that in a process without transfer of matter, the change in internal energy equals energy gained as heat less work done by the system. An equivalent statement is that perpetual motion machines of the first kind are impossible. Energy can be transformed but cannot be created or destroyed. The second law refers to a system of matter and radiation initially with inhomogeneities in temperature. Entropy increases as constraints are removed, eventually reaching a maximum value at thermodynamic equilibrium. The many versions of the second law all express general irreversibility of transitions involved in systems approaching thermodynamic equilibrium. The third law states that as the temperature of a system approaches absolute zero, all processes cease and entropy approaches a minimum value. Absolute zero is minus 273.15 degrees Celsius.
Classical thermodynamics describes states of thermodynamic systems at near-equilibrium using macroscopic measurable properties. It was used to model exchanges of energy, work and heat based on the laws of thermodynamics. A microscopic interpretation of these concepts was later provided by statistical mechanics. Statistical mechanics emerged with development of atomic and molecular theories in late 19th century. Ludwig Boltzmann set out foundations of statistical thermodynamics alongside James Clerk Maxwell and Max Planck. Rudolf Clausius and J. Willard Gibbs also contributed to this field. This field relates microscopic properties of individual atoms to bulk properties observable on human scale. Josiah Willard Gibbs published three papers between 1873 and 1876. His most famous paper On the Equilibrium of Heterogeneous Substances showed how thermodynamic processes could be graphically analyzed. He studied energy, entropy, volume, temperature and pressure to determine if a process would occur spontaneously. Pierre Duhem wrote about chemical thermodynamics in the 19th century. Chemists such as Gilbert N. Lewis applied mathematical methods of Gibbs to analysis of chemical processes in early 20th century.
The initial application of thermodynamics to mechanical heat engines quickly extended to study of chemical compounds. Chemical thermodynamics studies nature of role of entropy in process of chemical reactions. The primary objective is to determine spontaneity of given transformation. Thermodynamics applies to various topics including physical chemistry and biochemistry. It drives phase transitions and mechanical engineering systems like jet engines. A system in which all equalizing processes have gone to completion is said to be in state of thermodynamic equilibrium. Systems in equilibrium are much simpler than systems not in equilibrium. Often when analyzing dynamic process, simplifying assumption is made that each intermediate state is at equilibrium. This produces reversible processes developing so slowly as to allow each step to be an equilibrium state. Non-equilibrium thermodynamics deals with systems not in thermodynamic equilibrium. Most systems found in nature are not in stationary states. They are continuously subject to flux of matter and energy to and from other systems. Many natural systems remain beyond scope of currently known macroscopic thermodynamic methods today.
Constantin Carathéodory presented a purely mathematical approach in 1909. His work Investigations on the Foundations of Thermodynamics used Pfaffian systems and concept of adiabatic accessibility. In this formulation, concepts such as heat, entropy, and temperature derived from quantities more directly measurable. Theories that came after differed by making assumptions regarding processes with arbitrary initial and final states. Axiomatic thermodynamics aims to describe thermodynamics in terms of rigorous axioms. It finds mathematically rigorous way to express familiar laws of thermodynamics. An idealized thermometer defines temperature using sample of ideal gas at constant pressure. Volume of such sample serves as indicator of temperature according to ideal gas law pV equals nRT. A calorimeter measures and defines internal energy of system. A thermodynamic reservoir is system so large its state parameters not appreciably altered when brought into contact with system of interest. Earth's atmosphere often used as pressure reservoir. Ocean can act as temperature reservoir when used to cool power plants. Conjugate variables include pairs like pressure-volume and temperature-entropy. Product of two equaling amount of energy transferred. Five most well known potentials are Helmholtz and Gibbs energies among others.
Common questions
Who built the world's first vacuum pump in 1650?
Otto von Guericke built the world's first vacuum pump in 1650. He demonstrated a vacuum using his Magdeburg hemispheres to disprove Aristotle's supposition that nature abhors a vacuum.
When did Sadi Carnot publish Reflections on the Motive Power of Fire?
Sadi Carnot published Reflections on the Motive Power of Fire in 1824. The book outlined basic energetic relations between the Carnot engine and motive power and marked the start of thermodynamics as a modern science.
What is absolute zero temperature in degrees Celsius?
Absolute zero is minus 273.15 degrees Celsius. The third law states that as the temperature of a system approaches this value, all processes cease and entropy approaches a minimum value.
Which scientists developed statistical mechanics in the late 19th century?
Ludwig Boltzmann set out foundations of statistical thermodynamics alongside James Clerk Maxwell and Max Planck. Rudolf Clausius and J. Willard Gibbs also contributed to this field which relates microscopic properties of individual atoms to bulk properties observable on human scale.
How does the second law of thermodynamics define entropy increase?
The second law refers to a system of matter and radiation initially with inhomogeneities in temperature where entropy increases as constraints are removed. It eventually reaches a maximum value at thermodynamic equilibrium expressing general irreversibility of transitions involved in systems approaching thermodynamic equilibrium.