Читать книгу The Handy Chemistry Answer Book - Justin P. Lomont - Страница 10

What is the earliest historical evidence of the study of chemistry?

Although they didn’t call it chemistry, people from ancient civilizations used chemical reactions in many aspects of their lives. Metalworking, including the extraction of pure metals from ores, and then combining metals to make alloys, like bronze, left many artifacts of early man’s chemistry experiments. Pottery, including the production and use of various glazes, fermentation to make beer and wine, and pigments and dyes for cloth and cosmetics are all evidence that man has always been fascinated by the ability to change matter.

Where was early chemistry developed?

While many civilizations learned how to make dyes and pigments, or ferment fruit into wine, the earliest theories about atoms and what makes up the chemical world came from ancient Greece and India. Leucippus in Greece and Kanada in India both came up with the idea that there must be a small, indivisible part of matter. The Greek word for “uncuttable” is atomos, clearly the root of the modern term atom. Kanada’s term for this similar concept was “paramanu” or simply “anu,” the indivisible element of matter.

What does the city of Miletus have to do with chemistry?

Miletus, one of the Greeks’ greatest cities, was located on the western coast of what is now Turkey and was home to where some of the earliest ideas about chemistry were recorded. During the sixth century B.C.E., the Milesian school of thought was founded, and the musings of three philosophers survived into the modern era: Thales, Anaximander, and Anaximenes. Thales thought the most basic building block of the universe was water and that the Earth floated on top of this celestial water. Anaximander challenged both of these ideas, proposing that the universe was born when fire and water (or hot and cold) separated from one another and that the Earth simply floated on nothing. Anaximenes, who was a friend or perhaps student of Anaximander, countered that air was the most basic substance and that air condensed to form water and evaporated to reverse that process.

Who first proposed the idea of elements?

Plato is often given this accolade as he was the first to use this term for his description of the five basic shapes that he believed made up the entire universe: tetrahedrons, icosahedrons, dodecahedrons, octahedrons, and cubes. He went on to ascribe each shape to a basic element, borrowing from Empedocles (see next question). The tetrahedron was fire; icosahedron, water; dodecahedron, aether; octahedron, air; cube, earth. While this association of basic geometrical shapes to the nature of the Universe obviously didn’t work out for him, Plato’s ideas did lead Euclid to invent geometry.

What did Empedocles believe were the four basic elements?

A Greek named Empedocles (who was not from Miletus, but rather Sicily) was the first to propose the four basic “elements.” These four elements were earth, air, water, and fire. These elements had a much different definition from that which chemists use today (which we’ll get to later). Unlike the modern definition of an element, Empedocles’ understanding of an element did not require it to be a pure substance. Water, for example, was obviously not the only liquid Empedocles had ever encountered. Earth represented solids, water represented liquids, air represented gases, and fire represented heat.

What fifth element did Aristotle add?

Although Empedocles is understood to have been the first to propose the four basic elements, Aristotle is sometimes given this credit. Aristotle did propose a fifth basic element though, which he called aether. Aether was a divine material that Aristotle said made up the stars and other planets in the sky.

The earliest theories of the atom came about in ancient Greece, where philosophers correctly surmised that there were different kinds of atoms and that they contained mostly empty space—all centuries before the invention of the microscope!

When did the theory of the atom come about?

The idea of the atom was originally proposed by ancient scholars. The philosophers Democritus and Leucippus are often credited with proposing the early notions of the atom, including the ideas that many different kinds of atoms exist, that there is a substantial amount of empty space between atoms, and that their properties are responsible for the properties of materials we see and interact with. For centuries, ideas about the structure and properties of the atom were based largely on conjecture and logical arguments, and it wasn’t until the 1800s that experiments began to allow atomic theory to advance to where it is today.

What is an element?

An element is the most basic form of a chemical substance. If you have an object made of a pure element, all of its atoms have the same number of protons (we’ll discuss what this is more a little later) and the same basic chemical properties. There are not many objects that we encounter on a daily basis that are actually composed of only a single element—most things are formed from atoms of several types of elements bonded together.

What separates ancient and modern chemistry?

While there’s not a clear, punctuating distinction between ancient and modern chemistry, there are a few major differences that separate the two. Modern chemists describe the world in terms of atoms, molecules, and electrons and have a relatively complete understanding of the basic particles that make up matter—at least insofar as is necessary to describe chemical transformations. Ancient chemists didn’t have this information and relied less on experimental evidence and more on theory and mythology. For example, ancient chemists sought the Philosopher’s Stone (see below), for which there was no verifiable evidence, but they were attracted to it for its mythological power to preserve youth.

Who ran the first chemistry experiment ever?

Jābir ibn Hayyān, known as “Geber” in Western texts, was probably the world’s first alchemist to run actual experiments. Jābir lived during the eighth century in what is now Iran, and like alchemists before and after him, was fascinated by the prospect of changing one metal into another and by creating artificial life. To Aristotle’s four elements, Jābir added sulfur and mercury, and proposed that all metals were made of differing ratios of these two elements. He was the first to emphasize the importance of rigorous experimentation and is credited with describing many common lab techniques and equipment.

What is metallurgy?

Metallurgy is the branch of science that deals with the properties of metals composed of both pure elements and those of mixtures of metallic elements (which are called alloys). It represents one of the first efforts to manipulate and understand how elemental composition of a substance affects its physical properties.

What is bronze?

Bronze is an alloy of copper and tin that may contain up to one-third tin. Early civilizations used bronze because it could make stronger, more durable tools than stone or pure copper.

How did ancient civilizations make bronze?

Tin had to be mined in the form of an ore and then purified through a process called smelting. Once the tin was pure, it could be added to molten copper, in whatever ratio was desired, to make bronze for use in things like tools and weapons.

What is iron smelting?

Smelting is a method for extracting a pure metal from an ore (an ore is a rock made up of metals and other minerals). In smelting, a chemical transformation may be used to purify the metal by changing the oxidation state of metals in the ore (we’ll get into more detail on what an oxidation state is later in the book). The smelting of iron dates back to ca. 1000 B.C.E. (or maybe even earlier), and it typically involves first heating the raw material in a furnace called a bloomery. This produces a soft iron material that can be shaped. A hammer is often used to remove other impurities from the soft metal before allowing it to harden to form a relatively pure form of iron.

What is meteoric iron?

Meteoric iron is just what the name sounds like: it’s iron that comes from meteors. For early civilizations, meteoric iron was one of the few available sources of relatively pure iron (that is, prior to when the extraction of iron from ore was discovered). Meteors containing meteoric iron are composed of mostly nickel–iron alloys. Iron meteorites often have a distinct appearance, and they are typically much easier to recognize than other types of meteorites. For this reason, they are discovered more often than other types of meteorites. Iron meteorites actually account for all of the largest meteorites that have been discovered.

What is alchemy?

Alchemy was among the earliest practices of a chemical science, and, in a way, it can be considered a predecessor to the modern science of chemistry. Alchemy is somewhat different than a modern science, though, in that it also has roots in mythology and spiritualism. Practitioners of alchemy were known as alchemists. Among the primary goals of alchemists were to find a method or material that could convert inexpensive metals into precious gold, as well as to find an elixir of life, which could make a person both youthful and immortal. Myths told of the existence of such materials and of the possibility of such feats; the goals of alchemists were based largely on these myths. In medieval times, alchemists could be found in many countries around the world, and those in different regions held somewhat different beliefs. In the western world, people were still considering how to make metals into gold as recently as the late 1700s.