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[1.0] The Era Of Alchemy

v1.3.0 / chapter 1 of 15 / 01 jun 16 / greg goebel

* The science of chemistry suffered through a long prehistory, in which "alchemists" pursued such mirages as the transmutation of lead into gold and elixirs to grant immortality. Although the work of the alchemists was heavily dominated by nonsense, over time they acquired a growing level of practical skills that would provide a basis for a more rigorous science.

the alchemist


[1.1] DIM BEGINNINGS
[1.2] THE ALCHEMISTS
[1.3] THE RISE OF SCIENTIFIC IDEAS
[1.4] FOOTNOTE: BASIC DEFINITIONS IN PHYSICS & CHEMISTRY

[1.1] DIM BEGINNINGS

* There came a time in the distant past when people became curious about how the world around them actually operated, and decided to try to figure out the rules by which it worked. One of the significant items on the list was the question of what the world was made of: there was earth, water, and sky, or in more general terms solid, liquid, and vapor. The earth contained a wide range of different substances with different properties -- metals that could be shaped into tools and weapons, coal that could be burned, stone that could be carved into statues.

The first tools made by humans were fashioned from stones, wood, antlers, and other materials that were handy. Stone Age technologies could be surprisingly sophisticated given the limitations of the materials, but the limitations were fairly severe. Humans then began to obtain bright metals like gold and particularly copper from the earth, to fashion them into jewelry, utensils, tools, and weapons.

Then, no doubt by accident, they found that heating certain bluish minerals would transform them into copper; this was the origin of "smelting" of metallic ores. Copper was easily worked -- in fact too easily worked, too soft to be practical for many applications. It was eventually found that mixing copper with the dull metal tin produced bronze, a much tougher material. Bronze was later in turn outmatched by an even stronger metal, iron. Originally, iron was probably discovered in more or less pure form from fragments of metallic meteorites, but eventually humans began to smelt iron from earthly ores. How anyone ever figured out how to do this is unclear, since smelting iron requires a much hotter fire than needed to smelt copper, demanding a certain technological sophistication, using a fire in a pit lined with charcoal and blown with a bellows system.

While societies advanced through the Stone, Copper, Bronze, and Iron ages they also acquired other new materials, such as ceramics for pottery, glazes for pottery, and glasses for windows and utensils. They made perfumes, makeup, paints, dyes, medicines (some of which were even effective, though sometimes they were dangerous), and poisons, and learned how to ferment fruits and grains to make alcoholic beverages. Generally, these discoveries were made by practical artisans, but many early societies featured a caste of priests whose temples served as educational establishments, sites where knowledge could be accumulated, organized, and passed on. The priests became the ancestors of modern scientists.

The society of classic Greece produced what might be thought of as the first real scholars: individuals whose lives were devoted to the pursuit of knowledge about the world. In about 600 BCE, Thales (~624:546 BCE) suggested that the material world was based on water, which could solidify to form earth, or vaporize to form air. Later Greek thinkers expanded this idea to define four "elements": earth, air, fire, water. Although different philosophers proposed that one element or another was fundamental, by the time of the influential Greek philosopher Aristotle (384:322 BCE) the consensus was that all four were fundamental, with Aristotle adding a fifth "perfect" element, the "aether", superior to the other four, out of which luminous celestial bodies were made. The four earthly elements had properties of hot or cold, dry or most, with the system arranged as:

   FIRE    hot     AIR

   dry    AETHER   moist

   EARTH   cold    WATER

Fire was hot and dry, air was hot and moist, water was moist and cold, and earth was cold and dry.

In the 4th and 5th centuries BCE, one Greek philosopher named Leucippus and his student Democritus suggested that substances were based on indivisible units, which Democritus called "atoms"; according to this view, matter could be divided down repeatedly, but there had to be a level of "granularity" below which it couldn't be divided further. A later Greek philosopher named Epicurus (341:270 BCE) elaborated on the notion, which was documented by the Roman poet Lucretius (~99:55 BCE) in his essay DE RERUM NATURA (ON THE NATURE OF THINGS) in the 1st century BCE. However, Aristotle believed that matter was indefinitely divisible, and nobody would really challenge Aristotle's views for centuries.

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[1.2] THE ALCHEMISTS

* One of the implications of the theory of elements was that one substance could be changed into another by changing the proportions of its constituents; for example, lead might be turned into gold. Generations of "alchemists" pursued the goal of creating gold and finding elixirs of eternal life, working in the West, India, and in China. The search was futile, as we know now -- elixirs of eternal life had an ironic tendency to be toxic, even fatal -- but the alchemists did make many useful discoveries along the way. It also should be realized that even though in modern times any person with a workable education laughs at the idea of turning lead into gold, it didn't seem so unreasonable in ancient times, since lead and gold seemed very much like the same kind of material, being soft and dense metals, differing only in color.

However, the alchemists would ultimately acquire a reputation as frauds and conmen, using sleight-of-hand tricks to get backing from gullible patrons. Indeed, during the Roman empire alchemy would be more or less suppressed in the West, partly because of the prevalence of charlatans, but also because the authorities feared that if anyone actually could change lead into gold, it would create economic chaos. In addition, alchemy seemed something like a pagan practice, possibly involving deals with the Devil, and so there was a Christian religious prejudice against it as well.

The Romans had possessed substantial practical skills in chemistry, inherited from the Greeks and given refinements, and much would be lost in this time. For example, the Romans had known how to make concrete and construct large buildings with it, a skill that wouldn't be rediscovered until the 19th century.

* Alchemy did survive in independent forms in China and India. The rise of the Islamic Empire in the 7th and 8th centuries led to a cultural explosion as ideas from different regions mingled together. Islamic scholars -- the term is a little inexact, some of the scholars involved being Zoroastrians and other non-Muslims -- gave Greek texts careful examination, and also learned of Indian and Chinese alchemical thinking.

The Islamic alchemists were theoretically no more on the right track than Aristotle, suggesting that metals were composed of a "principle" of fluidity and volatility, most significantly exhibited by the liquid metal mercury, and a "principle" of combustion and corrosion, most significantly exhibited by sulfur, with different metals containing different proportions of these principles. The idea was that different combinations of mercury and sulfur could produce any type of metal. Eventually, a "principle" of solidity was added, most significantly exhibited by salt.

Of course, the Islamic alchemists came no closer to turning lead into gold, but they were careful and methodical researchers. Very significantly, they stressed the need for schemes of quantitative measurement using the laboratory balance and other simple instruments, and they did much to refine chemical processes with their recipes. Among their significant innovations were tools for distillation.

Distillation is a process of separating a liquid mixture by heating it: the liquid in the mix that has the lowest boiling point vaporizes first, to be cooled and collected. The best-known distillation is the concentration of ethanol, or grain alcohol, for alcoholic beverages, but it is a fundamental and important technique of chemistry across the board. Distillation was nothing new -- clay boiling pots are known from thousands of years ago that feature a lid and a trough around the edge where distillates could collect -- but the Islamic scholars advanced the technology for distillation considerably. Islamic alchemists also introduced more effective methods of smelting ores, manufacturing paper, and producing glass.

One of the pioneers of Islamic alchemical studies was Jabir ibn-Hayan (~760:860), later known in Europe as "Geber". He wrote a great deal, and his writings were both, in general, clear and practical, outlining preparations of metals and distillations of acetic acid, found in vinegar, the only acid generally available at the time.

One of the most prominent of the Islamic alchemists, a Persian named Al-Razi, later known in Europe as Rhazes (850:923), codified much of his science in a practical text titled SECRET OF SECRETS. The book gave a detailed description of basic chemical tools available at the time, such as vials and beakers, lamps, furnaces, tongs, mortar and pestle, and so on. It might have all been simple gear, but it amounted to a very useful toolkit, and in fact if Rhazes had been brought forward in time to a chemistry lab of, say, 1850, he would have found most of it perfectly familiar.

Al-Razi focused more on medicinal alchemy than Jabir, and a later Persian alchemist named Ibn-Sina (979:1037), known in Europe as "Avicenna", built on this knowledge to become the most famous physician of the Middle Ages. However, Avicenna was the last of the great stars of early Islamic science, since the great empire founded by Mohammed was fragmenting and coming under pressure from foreign invaders. The golden age of Islamic culture faded out.

* Among the foreign invaders were Europeans. The First Crusade began in 1096, with periods of combat continuing intermittently for about two centuries until the European presence was finally pushed out. Between times of major hostilities, however, there was some diffusion between cultures, with Europeans taking an interest in Islamic learning, translating Arabic works into Latin, and Islamic knowledge finding its way into Europe. By the 13th century, Europeans were beginning to use the knowledge of the Islamic scholars to recover the ground they had lost, and then move on to new discoveries.

The prominent English scholar Roger Bacon (1214:1292) promoted the concept that research into natural law should be based on measurements, experimentation, and mathematical analysis, helping establish the basis of modern science. He also created an encyclopedia whose entries included a formulation for "black powder (gunpowder)", a mixture of charcoal, sulfur, and saltpeter (potassium nitrate or KNO3 -- assigning modern chemical formulas here is getting a bit ahead of the story, but it makes the narrative a bit easier to follow). Bacon was sometimes thought to have actually invented black powder; however, the Chinese had known about it for centuries, and had improved the formulation over that period of time through trial and error. Bacon's description gave the contemporary Chinese formulation, showing that the idea had migrated from China to Europe, presumably through the writings of the Islamic scholars. Black powder would have the greatest impact on human culture of any chemical discovery of that era.

The author of the most comprehensive European work on alchemy of this period remains unknown, since he signed his work using the name of Geber. The "False Geber" was apparently a Spaniard, with his writings dating from about 1300. His documents were the first to describe sulfuric acid (H2SO4) and nitric acid (HNO3). These "mineral acids" were far more powerful than the weak acids that had been used in previous centuries, providing a very powerful tool for experiment and industry.

* Unfortunately, the resurrection of European alchemy also led to the revival of alchemical charlatans and con-artists, and so in 1317 Pope John XXII banned the practice. This time, however, the suppression of alchemy didn't stick. European nations were beginning to reach out across the oceans, contacting distant lands and staking out colonies, with one effect being to undermine the social status quo. In the 15th century, Johann Gutenberg (~1397:1468) introduced the "moveable type" press, permitting the mass printing of relatively low-cost books, helping to bypass the stranglehold of scholarly organizations on the spread of knowledge.

By the 16th century, the writings of the Polish scholar Nicholas Copernicus (1473:1543) were proposing that the Earth orbited the Sun instead of, as had been thought back to the time of the Greeks, the other way around. Similarly, the Flemish anatomist Andreas Vesalius (1514:1564) published a text on human anatomy that was far in advance of anything that had come before. Such assaults on the authority passed down from the Greeks also did much to undermine the status quo.

In some cases, this assault on tradition was reluctant; Copernicus, for example, had arranged for his work to be published only after his death. In other cases, it was thoroughly deliberate, one of the most spectacular cases being a Swiss scholar who called himself "Paracelsus", actually named Theophrastus von Hohenheim (1493:1541). Paracelsus was a windy, egotistical, obnoxious sort who associated with the disreputable and thrived on controversy. His self-awarded name of "Paracelsus" meant "Superior to Celsus", Celsus being a well-known medical writer of Roman times. Paracelsus was focused on medical alchemy, developing his own flavor, which was called "iatochemistry". His ideas were recorded in the book ALCHEMIA, published by a German scholar named Andreas Libavius (1555:1616) in 1597 and regarded by many as the first text on chemistry.

paracelsus

Despite his eccentricities, Paracelsus was no mere crank. Although he retained many alchemical notions -- such as a belief in the "principles" of mercury, silver, and salt established by Islamic scholars -- he emphasized the need for quantitative knowledge, investigating diseases such as goiter and syphilis in detail and proposing treatments with drugs. His dedicated assault on tradition opened the door to new ways of looking at things, and he is now regarded as not merely a important figure in the history of chemistry, but also in the history of pharmacology.

Another major figure in the development of European chemistry was a German scholar named Georg Bauer (1494:1555). His last name meant "farmer" in German, and so he wrote under the name "Agricola", Latin for "farmer". His book DE RE METALLICA (OF METALLURGY) was published in 1556 and compiled all that he could find out about mining and metal processing. It was a highly practical book, illustrating the advances obtained since the days of Aristotle.

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[1.3] THE RISE OF SCIENTIFIC IDEAS

* The quantitative basis for chemical studies was extended in the next century. A Belgian iatochemist named Jan Baptista van Helmont (1577:1644) performed some of the first modern experiments in chemistry, for example showing that a specific quantity of sand could be fused with alkalis -- the leachings of plant ashes, which we now know to consist of KOH, K2CO3, NaOH, and Na2CO3 -- to produce glass, and that the glass could be treated with acid to restore the original quantity of sand. Van Helmont was the first to imply the chemical principle of "conservation of mass", meaning that materials that entered into and resulted from chemical reactions balanced in weight, with nothing being either created or destroyed.

Van Helmont also showed the burning of wood gave off a vapor, which we now know as carbon dioxide, leading to the notion that "air" was not elemental, as had been long supposed, but might be composed of a mixture of different vaporous constituents. He gave them the name of "gas", a Flemish pronunciation of the Greek term "chaos", the material out of which the Universe had been formed. However, he had no means of isolating or examining gases and couldn't follow up his ideas in detail. Van Helmont also conducted experiments that led to, from the modern point of view, laughably wrong conclusions. For example, he raised a willow tree in a pot, providing it with nothing but water, and concluded that it had been generated by water itself. He never imagined that the tree might be extracting part of its sustenance from the air as well.

Despite his errors, van Helmont had succeeded in advancing the state of knowledge. An Italian scholar named Evangelista Torricelli (1608:1647) helped add to this advance by demonstrating the "mercury barometer". This was a glass tube, sealed at one end and open at the other, that was partly filled with mercury and then turned with the ends upward. The mercury fell down from the sealed side, leaving a vacuum behind it, and rose in the open side. The mercury on the sealed side didn't fall down to the level on the open side, however, meaning the air itself had a certain amount of weight, with the weight measurable as the discrepancy in the heights of the mercury, or "inches of mercury". The number of inches of mercury fell when the barometer was taken to higher altitude and rose again at lower altitude. Previously, concepts of air had been fuzzy, but now it was demonstrated to clearly be a form of matter.

A German physicist named Otto von Guericke (1602:1686) followed up this discovery in turn by developing a vacuum pump, which he used in 1654 to evacuate a metal sphere made of two half-shells fitted together. In a famous demonstration, he showed that the pressure of the atmosphere holding the two halves together was so great that teams of horses could not pull them apart. Aristotle had proclaimed that "nature abhors a vacuum", insisting that such a thing was impossible; the fact that it was clearly not further helped undermine the grip of Aristotle on thinking. It also helped promote the long-lost atomic ideas of Democritus, who had correctly envisioned air as particles bouncing around in a vacuum. The atomistic writings of Lucretius had resurfaced in the 15th century, and made a convert in the form of the French philosopher Pierre Gassendi (1592:1655), who spread the word.

* Gassendi, however, simply debated the idea as a philosophical notion, much as the Greeks and Romans had. To actually make progress required that somebody start doing useful experiments, or at least start thinking about them. In 1661 the Irish scholar Robert Boyle (1627:1691), who had been influenced by Gassendi's writings, published a book titled THE SCEPTICAL CHYMIST, in which he proposed that elemental materials had to be determined by experiment, with the experiments identifying materials that could not be broken down further. Those that were not elementary were obviously "compounds" of elementary materials. Boyle didn't really have much idea of what the real elements were, but he did use von Guericke's invention, the vacuum pump, to perform pioneering studies on the behavior of air. Boyle established a major step towards modern chemical theory by proposing in 1662 that the pressure and volume of a gas were inversely related:

   P1 * V1  =  P2 * V2

"Boyle's law" was one of the first correct quantitative laws of chemistry to be devised. His use of the term CHYMIST and not ALCHYMIST in the title of his book demonstrated a break with the past, and his attempts to establish a rigorously quantitative, experimental basis for chemistry fit in with the spirit of the times. Early in the century, the Italian scholar Galileo Galilei (1564:1642) performed groundbreaking studies of motion and other basic physical concepts, which were the basis on which the brilliant English scholar Isaac Newton (1642:1727) established his "three laws of motion" and a general basis for modern physics.

That basis also would underlie modern chemistry, providing definitions of such previously vague concepts as force and energy, but Newton himself made few direct contributions to chemistry: most of his endeavors along that line focused on traditional alchemy and remain obscure, being something of an embarrassment to his memory. Incidentally, Boyle was also still hooked on alchemical ideas, providing a bit of unintended humor to later generations by lobbying for the repeal of an English law against transmutation of metals into silver and gold, arguing to the authorities that the law inhibited important research.

Newton's alchemical studies accomplished little of lasting value, but his most famous work, PRINCIPIA MATHEMATICA, published in 1687, included among its far-ranging topics a theoretical investigation of Boyle's law that featured a significant conclusion. The fact that a gas was so highly compressible suggested that it might well be composed of a large number of particles -- atoms -- dancing around and bouncing against each other in an otherwise empty volume of space. Boyle and Newton had taken the first step towards placing the idea of atoms on a rigorous basis.

* Newton's work did much to put physics on its modern course. It would take chemistry about another century to achieve a similar critical mass. Partly this delay was due to the excess baggage imposed on the science by alchemy, but there was (and still is) also a major difference between physics and chemistry.

Physics is focused on the fundamental laws of nature, while chemistry is focused on how those laws are applied in the infinite variations of arrangement of matter. It is for this reason that there has always been an undercurrent of tension -- sometimes even hostility -- between physicists and chemists, with some physicists regarding chemistry as subordinate, an applied science, riding on the coattails of the fundamental truths of physics. The New Zealand-born modern British physicist Ernest Rutherford (1871:1937) famously illustrated this attitude in an extreme form when he stated that "all science is either physics or stamp collecting." Rutherford, incidentally, also clearly considered experimental physicists superior to theoretical physicists.

Of course this argument can be flipped around, with physicists seen as focusing on simplifications and generalities, while chemists try to come to grips with the messy complexities of the real world. The argument is in itself merely tiny-minded to outsiders, but it does point out that chemistry is about matters that are inherently complicated -- the worst case being the chemistry of life itself, which is of appalling complexity -- that are very difficult to render down to comprehensive, hard rules. Progress in chemistry would rarely be revolutionary, instead advancing in small increments as continuously refined experiments gave chemists an increasingly solid grasp of the bewilderingly varying forms of matter. In modern times, chemists still operate by a matrix of overlapping physical models and practical rules of thumb, an approach that physicists often find exasperating -- even to the sensible among them who realize that the untidiness is inherent in the subject, and there's no way around it.

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[1.4] FOOTNOTE: BASIC DEFINITIONS IN PHYSICS & CHEMISTRY

* Having introduced Newton, it is appropriate to introduce a few basic definitions from elementary physics useful for chemistry and some basic chemical concepts, along with some metric measurement units. The metric system wasn't invented until the late 18th century and didn't become all but universal until well into the 20th century, but use of older measurement systems in this narrative would cause useless confusion.

Readers can be assumed to understand the basic concepts of "length" and "displacement", measured in the metric system in "meters", and of "velocity", measured in the metric system in "meters per second". Among the fundamental concepts of physics are the concepts of "mass", "force", "acceleration", "momentum", "pressure", "work", "energy", and "power".

Everyone has an intuitive notion of the concept of mass as a measure of the amount of matter of an object: a brick has more mass than an empty box the same size. Mass is generally measured in "kilograms". A force is an action that accelerates, or changes the motion of a mass. For example, the force of a powder charge in a rifle cartridge accelerates a bullet from rest to its muzzle velocity. Force is measured in "newtons", while acceleration is measured in "meters per second squared". Newton's second law of motion states that there is a direct relationship between force and acceleration of a given mass:

   force  =  mass * acceleration

Once a mass is put into motion, it has a tendency to stay in motion, with this tendency quantified as "momentum", the product of mass and velocity, of course measured in kilograms by meters per second.

Pressure is simply the amount of force per unit area. It is measured in "pascals", or newtons per square meter. If ten newtons are applied to a square meter, there is a pressure of ten pascals. The pascal is something of a small unit in practice, and so the "bar", or 100,000 pascals, is used instead. A bar is almost the same as the older unit of an "atmosphere", which is 101,325 pascals, and the two can be regarded as equivalent for most purposes.

The notions of work and energy are complementary. The work done on a mass is the product of the force applied to an object and the distance over which the force is applied:

   work  =  force * distance

Work is measured in "joules", or newtons per meter. Energy is a capacity to do work, also measured in joules; for example, a mass suspended from a mast will be accelerated by the force of gravity after it is released until it hits ground, and a cocked spring-loaded gun will accelerate a ball if the trigger is pulled. In these two examples, the energy is "potential", waiting to be released, with the energy of the mass on the mast a simple product of the mass and the height, and the energy of the spring in the gun a simple product of the stiffness of the spring and the length of compression of the spring. Once the mass is put into motion, it acquires a certain "kinetic" energy by virtue of its motion, with this value given by:

  kinetic_energy  =  (1/2) * mass * velocity^2

It requires work to create potential energy, for example to haul the mass to the top of the mast or squeeze the spring in the gun, and work or the release of the potential energy can create kinetic energy. The amount of potential energy put into the system can be no greater than the amount of work used to create that potential energy, and the amount of kinetic energy created from work or the release of potential energy can be no greater than the original amount of work or potential energy. This is the "law of conservation of energy": energy may change forms, but it cannot be created or destroyed.

Power, finally, is the time rate of work. The work required to move a mass is the same no matter if it takes a short period of time or a long period of time, but the power is greater if it takes a short period of time. Power is measured in newton-meters per second or "watts".

All these concepts date back to the mid-19th century or earlier and they remain accepted as the truth, but in modern times physics has added some fine print to them. One was Albert Einstein's discovery that there was an equivalence between mass and energy, given by his famous equation E = MC^2, or in more detail:

   energy  =  mass * speed_of_light^2

-- where the speed of light is 300,000,000 meters per second. Mass can be converted to energy; energy can be converted to mass. That means that, strictly speaking, the "law of conservation of energy" is incorrect; it should be now thought of as the "law of conservation of mass-energy". However, for most purposes the older form of the law remains perfectly workable.

* There are four forces in the Universe, including the gravitational force that holds us to the Earth; the electromagnetic force that creates an attraction between, say, styrofoam packing peanuts and our fingers; and the strong and weak nuclear forces, which affect matter at the submicroscopic scale.

The electromagnetic force is the only one of these four forces that is really important in chemistry. The rules for the electromagnetic force are basically simple: materials can possess a positive (+) or negative (-) electric charge; if two objects have the same charge (++ or --) they repel, if they have an unlike charge (+-) they attract each other.

* This discussion gives concepts of basic physics, but chemistry has a slightly different focus for concepts such as work and energy than physics. In chemistry:

The fundamental laws remain the same for both physics and chemistry, it's just that chemistry expresses them somewhat differently, as discussed later in this document.

Having raised the issue of temperature, it should be noted that in the metric system temperature is measured in "degrees Celsius", a temperature scale in which water freezes at 0 degrees Celsius and boils at 100 degrees Celsius at an atmosphere of pressure. There is a temperature known as "absolute zero" that gives the limit of how cold something can be made, even in theory, and the value of absolute zero is -273.15 degrees Celsius.

There is an alternate "Kelvin" temperature scale in which the temperature increments are the same as they are in the Celsius scale, but the zero is assigned to absolute zero, meaning that water freezes at 273.15 degrees Kelvin and boils at 373.15 degrees Kelvin. In many problems, it's easier to do the arithmetic using degrees Kelvin than with degrees Celsius.

* Finally, before moving on it is useful to provide a few basic definitions for chemistry. Chemistry deals either with pure substances or mixtures of pure substances in solid, liquid, or gaseous form. Pure substances are those that can't be separated by mechanical means, while mixtures can. The ancient alchemists did understand in a somewhat fuzzy way that pure substances could be "compounds", created by the chemical combination of two or more other pure substances, and that such compounds could sometimes be restored to their constituent pure substances by chemical means.

Mixtures of metals are known as "alloys". It is also possible to create dispersed mixtures of solids in liquids, or liquids in liquids, with such mixtures called "solutions", involving a solid or liquid "solute" that is dissolved in a liquid "solvent". Water is the most common but not the only solvent. There are also "colloids", in which particles of one material are dispersed in another material -- solid particles in liquid (mud or paints), solid particles in gas (smoke), gas in liquids (foams), liquids in gases ("aerosols" like household sprays), and so on. In addition, gases or liquids can be "absorbed" into internal spaces inside solids, or "adsorbed" onto the surface of solids.

Although the ancients believed that solids, liquids, and gases represented different elements, we now know is nothing elemental about them; they are just different states of matter. Ice, or solidified water, can be heated up to its "melting point" to melt into liquid water, and liquid water can be heated further to its "boiling point" to turn into steam, or gaseous water. The transitions between these states of matter are called "phase changes".

Distinct materials can be characterized by specific features. All materials have such features as color, density, electric conductivity, and "specific heat", or the amount of energy required to raise a kilogram of the material a degree Celsius in temperature; solid materials have features such as hardness and ductility, as well as internal arrangement, either as disorderly "amorphous" materials or orderly "crystalline" materials; liquid materials have features such as viscosity, or ability to flow.

One last little detail on chemistry: every now and then a chemistry document will refer to an "IUPAC" standard. That stands for the "International Union of Pure & Applied Chemistry", which is a modern global organization whose committees define standards for chemical nomenclature and practice.

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