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5500 BCE
Copper Smelting
When early civilizations learned that heating rocks can be used to extract certain ores, they began to make tools from copper, including the earliest known copper ax. -
Period: 3000 BCE to 1000 BCE
Ancient Chemistry
Early civilizations were extracting metals from ore, made pottery and glazes, fermented alcohol, extracted chemicals from plants, and made things like alloys, soaps, and glass. The first bits of gold were discovered "loose" in a cave in Spain, dating back to about 40,000 BCE and other metals like silver, copper, and tin were discovered later around 3,000 BCE. These later metals were used to make prized daggers. -
2900 BCE
The Beginnings of Glass and Metalurgy
The discovery of fire led to the purification of glass and the creation of metal tools in early Egypt. This also led to gold becoming a precious metal. -
Period: 500 BCE to 500
The Beginnings of Alchemy
Alchemy's beginnings can be traced back to Hellenistic Egypt when the city of Alexandria was the center of alchemical knowledge because of the combinations of technology, religion, mythology, and philosophy, which later became alchemy. The city maintained its title through the Greek and Roman periods, when the first books on alchemy were being written in Egypt. -
Period: 460 BCE to 370 BCE
The Influence of Democritus
Democritus theorized that all objects are made of atoms that cannot be physically split, are indestructible, are different sizes and shapes, are always moving, and have only empty space between them. -
420 BCE
The Concept of Elements
Around this time, the Chinese had begun to hypothesize about the fundamental pieces of objects and substances, called atomism. They concluded that the four main elements are air, earth, fire, and water. -
Period: 384 BCE to 322 BCE
The Influence of Aristotle
Aristotle believed in the four primary elements, plus the aether, which is a divine substance that makes up the heavens and outter space. He refuted Democritus's atomic theories, leading to a debate lasting tens of centuries. -
Period: 1100 to 1500
The Revival of Alchemy
After alchemy's disappearance from ancient civilizations, it was revived by the Europeans in the 12th century, and old texts were translated from Arabic to Latin. Alchemists' goals were to find the connections between man and the universe, find the elusive element that transformed substances into gold (called the "philosopher's stone"), and to find new medicines. This led to the split that created more modern chemistry and our modern idea of alchemy. -
Period: to
The Beginnings of Modern Chemistry
The introduction of what would later become known as the Scientific Method came in 1605 from Sir Francis Bacon in "The Proficience and Advancement of Learning." Also in 1605, Michal Sedziwoj published "A New Light of Alchemy," proposing an idea for something in the air that allowed life to take place; what he was describing was Oxygen. Robert Boyle, a trailblazer in chemistry, was influenced by Jan Baptist van Helmont's work "Ortus medicinae," a book describing the law of conservation of matter. -
Period: to
Robert Boyle
Although Boyle's work primarily focused on alchemist principles, he helped separate chemistry and alchemy, and refine the scientific method for chemistry. Still, he is highly regarded as one of the first chemists and a father of chemistry. Boyle is also well know for Boyle's law and his publication "The Skeptical Chymist." -
Period: to
The Discovery of New Elements
1735 - Georg Brandt noticed a blue pigment in copper ore, later identified as Cobalt.
1751 - Joseph Black isolated carbon dioxide, which he called "fixed air."
1757 - Louis Claude Cadet de Gassicourt created cacodyl oxide, which he called "Cadet's fuming liquid."
1766 - Henry Cavendish isolated hydrogen, which he called "inflammable air."
1773 - Carl Wilhelm Scheele discovered oxygen, which he called "fire air."
1783 - Jose and Fausto Elhuyar isolated tungsten from reducing tungstic acid. -
Period: to
Antoine Lavoisier
Known as the father of modern chemistry, he is the mind behind the Law of Conservation of Mass, the idea that air is made of two main parts (oxygen and azote), the discovery that water is a compound of hydrogen and oxygen, the way elements and compounds are named, bleach, the first modern chemistry textbook, the idea that diamonds are crystalline carbon, and more. -
The Discovery of Electrical Charges
Benjamin Franklin discovered that electrical charges can be either positive or negative and that opposite charges attract each other. For a reason unknown, Franklin said glass-like substances were positive and more plastic-like substances were negative. -
Joseph Louis Proust
Prout discovered that chemical compounds always have the same proportions of elements by mass, known as the Law of Definite Proportions. For example, water (H2O) is made of 88.9% oxygen and 11.1% hydrogen. -
Period: to
John Dalton's Atomic Theory
Dalton determined that matter is made up of atoms which are indivisible and indestructible, all atoms of an element are identical (which has since been proven false), atoms of different elements have different properties and different masses, chemical compounds are made of atoms of different elements in simple whole numbers, and atoms cannot be created, nor destroyed. -
Period: to
Charles's Law
Joseph Louis Gay-Lussac began research in 1801 into the way gases expanded. He concluded that all gases at equal volumes expand the same with the same change in temperature. This law was named Charles's Law because Gay-Lussac decided to give credit for the discovery to Jacques Charles because he had come to a similar conclusion in the 1780s, but had not published it. -
The Discovery of Potassium by Electrolysis
Humphrey Davy had been experimenting with electrolysis using Volta's voltaic pile, trying to isolate new elements. In doing so, he discovered potassium. This was a big discovery in the 1800s because before this, there was no distinction made between potassium and sodium. Davy also isolated sodium for the first time in the same year. -
Hess's Law
Hess's Law, an early iteration of the Law of Conservation of Energy, was proposed by Germain Hess, and stated that energy changes in chemical processes only depend on the state of the starting and product materials, not on the pathway between the two states. -
The Cathode Ray Tube
William Crooks is noted for his work on CRTs, which was fundamental to atomic physics. Crooks showed that cathode rays travel in straight lines and produce phosphorescence when they come in contact with certain materials. These CRTs were vacuums inside, so when Crooks put a wheel in one and it spun from the rays, he knew that the rays must have mass. -
Gibbs' Phase Rule
Josiah Willard Gibbs concluded that matter is always in a state according to temperature, pressure, energy, volume, and entropy. Gibbs also concluded that states of matter were phases and the substances were components. -
The Continued Research of Cathode Ray Tubes
Sir John Joseph Thomson found that negatively charged plates in a cathode tube would deflect the rays and positively charged plates would attract the ray. With this information, Thomson concluded that the ray was made of negatively charged particles, which he called electrons. -
Period: to
The Famous Gold Foil Experiment
Ernest Rutherford stretched a sheet of gold foil over a tin can and coated the inside with a florescent paint. Then, he pointed positively charged alpha rays at it and expected the rays to go straight through the metal. He found that air and solids can disrupt the flow of alpha radiation, making them go off in different directions. This experiment was followed by several more experiments through 1913 where Ernest Rutherford, Hans Geiger, and Ernest Marsden tested how alpha rays were scattered. -
The Study of Radioactivity
Marie and Pierre Currie were the first to isolate polonium and radium from uranium ore. She and Pierre discovered how radioactive elements slowly changed into other elements through radioactive decay, leading them to believe there was something within atoms that gave them their unique identity. -
The Mass of Electrons
Robert Millikan and Harvey Fletcher created an experiment, called the oil drop experiment, where they suspended charged oil particles between two metal electrodes. They calculated the charge on the droplets, and then the mass, realizing that all of their masses were multiples of a fundamental constant, which they determined was 1.5924 × 10−19 Coulombs. -
Period: to
The Neutron Experiments
After various experiments with beryllium, James Chadwick learned that when a beam of radiation hits a substance with lots of protons, some get knocked off and they were easily detectable by a Geiger Counter. In 1932, Chadwick proposed that these may be the neutrons that had been proposed by Ernest Rutherford in 1920. Chadwick later discovered that, when separated from its element's nucleus, neutrons were unstable.
