Lavoisier on Constant Mass

In 1789, Lavoisier showed that the total mass during the course of a chemical reaction is unchanged. Rather the atoms simply “reorganize” themselves, kind of like the reshuffling of deck or cards.

Lavoisier’s 33 Elements

In 1789, Lavoisier published An Elementary Treatise on Chemistry where he describes 33 elements. The list begins with caloric and continues with light, oxygen, nitrogen and hydrogen.

Heat as “Caloric”

Pierre-Simon Laplace (1749-1827) imagined heat to be a fluid composed of particles, deemed by Antoine Lavoisier (1743-1794) as “caloric”.

Entropy and Atoms

Our understanding of the connection between entropy and the microscopic world of atoms is mostly due to the work of James Clerk Maxwell and Ludwig Boltzmann.

Clapeyron’s Reformulation of Carnot’s Work

In 1834 Émile Clapeyron (1799-1864), a former classmate of Carnot’s, published a paper in the Journal de l’École Polytechnique. Here he reformulated Carnot’s work using clear concise mathematics and a new graphical presentation for Carnot’s reversible heat engine (still taught today to every chemistry major taking a good physical chemistry class) that finally brought Carnot’s work to the attention of engineers, chemists and physicists.

Energy and Entropy

Energy and the first law that governs it can’t explain why certain processes tend in what apparently is a favored direction; for that we need entropy.

Einstein and The Quantum Ideal Gas

In 1925, Einstein made his last contribution to quantum theory (consider by many to be his last significant scientific contribution as well) with his work on the quantum ideal gas.

Clausius Discovers Entropy

Clausius formulated much of the original ideas of his theory on entropy in 1854. However, it wasn’t until 1865 that he actually named his new property “entropy”.

Energy, Entropy and the Universe

Whereas the universe keeps energy at a constant (energy is conserved), it continues to increase the entropy. Therefore, no process that occurs will ever result in an overall decrease in the entropy of the universe. The universes’ tendency of maximizing entropy is reminiscent of “a universal tendency to the dissipation of mechanical energy” as stated by Thomson, and Clausius noted the connection.

Galileo and Two New Sciences

In 1634, Galileo, now under guarded house arrest, and mourning the recent death of his beloved daughter, returned to his project of some twenty-five years prior to produce his final masterpiece Discourses on Two New Sciences.

Sound Waves, Diffraction, and Propagation

A sound wave will often travel from one room to another spreading out though an adjacent doorway where it’s then heard. This is an example of the wave property known as diffraction.

Newton Waited to Publish Opticks

In 1666, Newton bought his first prism with the motivation of disproving Descartes wave theory of light. In 1672, he gave a brief account of his findings, in the form of a letter, to the Royal Society, whereby – after a bit of convincing – it was published in the Philosophical Transactions of the Royal Society. Although not unanimous, Newton’s work met with much praise. However, one critic’s words would resound with Newton, thus beginning a lifetime feud.

Robert Hooke (1635–1703), who was considered the expert on the subject in England, sent a lengthy critique. In short, it pretty much said Hooke had performed all the same experiments, drawn different conclusions, and that Newton was outright wrong. In 1704, Newton finally published a full account of his theory of light in Opticks. To be sure, Newton had already drafted a treatise covering much of this work by 1672,

The Maxwell Distribution

Not all the atoms in a gas move at the same speed, but rather each atom takes on a speed lying in a specific range. For an ideal gas at equilibrium, this range is known as the Maxwell distribution. In 1860, Maxwell needed merely a single page to derive this amazing result, which also allowed him to calculate other important properties of a gas that matched with experimental observation.

Heat is Energy

Heat was the biggest stumbling block to a complete understanding of energy, remaining separate from it until around 1850 when the first law of thermodynamics was inducted.

Confusion About Energy

An understanding of energy in its entirety did not occur until well into the nineteenth century.

Particles in Motion

That the properties of gases could be explained by particles in motion had been advocated in 1738 by Daniel Bernoulli (1700-1782), who proposed a model that is very similar to the one in acceptance today.

The First “Atomic Theories”

The first “atomic theories” focused on a “primary element” responsible for creating all other matter. Heraclitus said it was fire, Thales of Miletus (c.624 BC–c.546 BC) said it was water, Anaximenes (c.585 BC–c.528 BC) thought it was air, and Empedocles finally unified these declaring there to be the four elements of air, earth, fire and water. Later Aristotle adopted Empedocles’ four elements and so it remained up until about the 17th century.

Particle, Corpuscle, Element and Atom

Through the 18th century the words particle, corpuscle, element and atom were all used synonymously to refer to the building blocks of matter. In fact, no more insight into what an atom was had been accomplished since (the Greek philosopher) Democritus’ description some two thousand years prior.

Collisions in a Gas

The particles (atoms, molecules) of a gas move farther and faster (in a given interval of time) than those of a liquid. As they do so, a single particle undergoes about a billion collisions every second with other particles.

Waves and Diffraction

A lower pitch sound, that is a sound wave with a longer wavelength (lower frequency), will diffract (or bend) around an object more than a higher pitch sound (a sound wave with a shorter wavelength and higher frequency). This means a lower pitch sound is more easily heard around an object that may be in front of the source of the sound than a higher pitch sound

Einstein’s Light Quanta Hypothesis Explains Physical Phenomenon

In his1905 paper, On a Heuristic Point of View Concerning the Production and Transformation of Light, Einstein showed how his newly introduced light quanta hypothesis could be used to interpret several well-known experimental observations, the most notable of these phenomena being the photoelectric effect.

Einstein’s Photon

The major theme of Einstein’s 1905 paper, On a Heuristic Point of View Concerning the Production and Transformation of Light, was that light (under certain circumstances) behaves as if it’s comprised of individual particles rather than waves. These particles, or “chunks” of light were originally called light quanta, and then later came to be called photons.

Einstein’s Light Quanta Hypothesis and The Nobel Prize

It was the first of Einstein’s 1905 papers, On a Heuristic Point of View Concerning the Production and Transformation of Light, which he referred to as “very revolutionary” – the only time he would ever say this about any of his work, in fact – and which, in part would win him the Nobel Prize in 1921.

Atomic Energy States are Discrete

The energy states available to atoms and molecules occur at specific intervals. In other words, they are discrete rather than continuous.