50 Fun Facts About Thermodynamics

How many laws of thermodynamics are there?

The zeroth law was added after the other three were already numbered, because renumbering them was impractical.

Which way does heat never flow on its own, according to a classic statement of the laws?

That everyday observation is one traditional way of stating the second law.

Which law of thermodynamics expresses the conservation of energy?

Energy can be transformed from one form to another but cannot be created or destroyed.

What is absolute zero on the Celsius scale?

The same point is −459.67 °F and 0 on both the Kelvin and Rankine scales.

Which temperature scale is defined with absolute zero as 0?

The Rankine scale also starts at absolute zero but uses Fahrenheit-sized degrees.

Who is known as the 'father of thermodynamics'?

His 1824 Reflections on the Motive Power of Fire was the only book he ever published.

Which physicist coined the word 'entropy' in 1865?

He chose a Greek word for transformation and deliberately made it sound like 'energy'.

The word 'entropy' was coined from a Greek word meaning what?

Clausius first called it Verwandlungsinhalt, transformation-content, before settling on the Greek-derived name.

Which practical problem drove the early development of thermodynamics?

Carnot's 1824 analysis of engines was later built upon by Kelvin and Clausius.

Who built the world's first vacuum pump in 1650?

He wanted to disprove Aristotle's claim that nature abhors a vacuum, and did so with his Magdeburg hemispheres.

Boyle's Law says which two gas properties are inversely proportional?

Boyle and Hooke noticed the correlation using an air pump built in 1656.

Denis Papin's 1679 'steam digester' was essentially an early what?

Watching its release valve bob up and down gave him the idea of a piston-and-cylinder engine.

Who developed the concepts of heat capacity and latent heat at the University of Glasgow?

James Watt was the university's instrument maker at the time and experimented alongside him.

Which innovation by James Watt greatly improved steam engine efficiency?

Watt conceived it while employed as an instrument maker at Glasgow alongside Joseph Black.

Who wrote the first thermodynamics textbook in 1859?

Originally trained as a physicist, he was a professor of civil and mechanical engineering at Glasgow.

What did Clausius's 1850 paper 'On the Moving Force of Heat' first state?

It earned him the title of one of the founding fathers of thermodynamics.

Which American published 'On the Equilibrium of Heterogeneous Substances' in the 1870s?

His graphical methods showed whether a process, including a chemical reaction, would occur spontaneously.

Who presented a purely mathematical, axiomatic thermodynamics in 1909?

His approach, using adiabatic accessibility, is often called geometrical thermodynamics.

A process that occurs with no heat exchange is called what?

A reversible adiabatic process also keeps entropy constant and is called isentropic.

What stays constant during an isobaric process?

Isochoric processes, by contrast, hold volume fixed.

What is held constant in an isochoric process?

It is also called an isometric or isovolumetric process.

An isenthalpic process occurs at constant what?

Isentropic, a reversible adiabatic process, is the one that holds entropy constant.

Per the zeroth law, if A and B are each at the same temperature as C, then what?

The law is tacitly assumed in every temperature measurement and justifies building thermometers.

Why is the zeroth law called 'zeroth'?

The first, second and third laws were already accepted, and renumbering them was impractical.

What does the third law say happens as temperature approaches absolute zero?

A consequence is that absolute zero cannot be reached in a finite number of steps.

Which pair are the 'thermal' conjugate variables in thermodynamics?

Pressure-volume are the mechanical pair, and chemical potential-particle number the material pair.

Which two potentials give the work available at fixed T and V, or fixed T and p?

They cannot be measured directly in a lab but can be computed from molecular thermodynamics.

A negative change in Gibbs free energy indicates what kind of process?

The relation is ΔG = ΔH − TΔS, with T in kelvin.

Who gave entropy its statistical meaning as a count of microscopic arrangements?

His logarithmic law carries a proportionality constant, now one of the SI's defining constants.

In what year did Boltzmann define entropy via the logarithm of the number of microstates?

The Boltzmann constant is the proportionality factor in that definition.

Who devised the information-theory version of entropy in 1948?

He was studying the size of information in a transmitted message.

Who extended entropy into quantum mechanics using the density matrix?

His Mathematische Grundlagen der Quantenmechanik built the rigorous framework for quantum measurement.

Entropy is said to imply an 'arrow of' what?

It is the only quantity in the physical sciences that seems to point in a particular direction of progress.

What is the only publication Carnot produced in his lifetime?

It attracted little attention until Émile Clapeyron's 1834 commentary reached Kelvin and Clausius.

Carnot was named after a poet from which country?

His father Lazare chose the name of the 13th-century poet Sadi of Shiraz.

At what age did Carnot die, of cholera, in 1832?

He died in relative obscurity in a sanatorium at Ivry, south of Paris.

Which French engineer's 1834 commentary rescued Carnot's work from obscurity?

It brought the ideas to Lord Kelvin and Clausius, who built the absolute temperature scale and entropy on them.

What does Carnot's theorem provide for any classical heat engine?

A Carnot cycle is reversible; run backwards, it works as a refrigerator or heat pump.

What are the four stages of a Carnot cycle?

Real engines that follow this cycle are rare, but it fixes the best efficiency any engine can hope for.

Who proposed the 'demon' thought experiment that seems to defy the laws of thermodynamics?

Maxwell himself, a devout man, only ever called it a 'finite being'; Kelvin supplied the name in 1874.

Who first called Maxwell's 'finite being' a demon?

He meant the Greek sense of a daemon working in the background, not a malevolent spirit.

Who argued in 1929 that the demon's need to measure molecules costs energy?

The insight linked thermodynamics to information; Landauer later pinned the cost specifically on erasing information.

In which book did Maxwell present his demon to the public in 1872?

It had first appeared in a letter to Peter Guthrie Tait in December 1867.

The 'heat death of the universe' is also known by what nickname?

It describes a universe at maximum entropy, with no temperature differences left to do work.

Whose 1850s ideas on mechanical energy loss gave rise to the heat death hypothesis?

He extrapolated the first two laws to the universe as a whole and derived a paradox against an infinitely old cosmos.

Which French astronomer suggested in 1777 that all bodies in the universe cool off?

He corresponded with Voltaire about it, judging Venus still too hot for life and Mars already too cold.

A machine that produces work with no energy input would violate which law?

It would produce work with no energy input; the second kind would turn heat wholly into work instead.

Bhaskara's 12th-century perpetual motion design was what type of device?

The overbalanced wheel remains one of the most recurring ideas among would-be inventors.

Which 17th-century bishop listed three power sources for perpetual motion machines?

The Bishop of Chester named chemical extractions, magnetic virtues and gravity as early as 1670.

What record-low effective temperature, in picokelvin, was set in 2021?

It was achieved by matter-wave lensing of rubidium Bose-Einstein condensates.