Chemistry

Introduction

For thousands of years scientists from different countries have been contributing important discoveries and ideas that shaped a modern science. This chapter looks at some important discoveries in the field of chemistry.

Where did it all begin?

Chemistry is the study of elementary particles. Elementray particles are the building blocks of matter. Matter is anything that has a mass and occupies a space. The word chemistry comes from the Greek word chemeia. This an ancient method of extracting medicinal substances from plants, and metals from rocks. Today, chemistry looks at the different uses of chemicals and their interactions with each other, production techniques and disposal methods.

The Ancient Greek scientist Democritus proposed that matter was made of indivisible particles, after his teacher pointed out that a beach looks smooth from afar but is really made of small grains of sand. He called his particles atomos, meaning 'cannot be cut'. Another ancient Greek scientist, Aristotle, believed that everything was made of four basic elements: fire, air, water and earth; and all matter had four properties: hot, cold, dry and wet.

Ancient scientists from Mesopotamia came up with the idea that metals were made of sulphur and mercury (chemical elements).

Alchemy was a Medieval practice which combined mysticism (belief in the supernatural) and chemistry. Alchemists were looking for a way to blend metals into gold and make an elixir (a sweet-tasting medicine) of immortality. English scientist Roger Bacon believed that alchemy should be used to create medicines and other materials to benefit humanity; however, the search for gold would rule alchemical research for centuries.

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A seventeenth century scientist, Robert Boyle, defined a chemical element to be a substance that could not be broken down. He also discovered the relationship between the pressure and volume of a gas, known today as Boyle's law.

An eighteenth century scientist, Johann J. Beecher, believed in a substance called phlogiston. Phlogiston is an imaginary element once thought to be given off when things burned. It was Antoine Lavoisier who disproved the Phlogiston Theory. He realized that oxygen was part of the air and it combined with substances as they burned.

The concept of molecules was first introduced in 1811 by Italian chemist Avogadro. A molecule is the smallest structural unit of matter. At the beginning of 19th century John Dalton published his Atomic Theory which stated that all matter is composed of atoms, which are indivisible. Russian chemist Dmitri Mendeleev came up with the periodic table of chemical elements. The periodic table is a chart that lists chemical elements by their atomic number, so that elements with similar chemical properties are grouped together.

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Later, the synthesis of urea (an organic compound of carbon, nitrogen, oxygen and hydrogen) by Friedrich Wöhler opened up a new field of chemical research, now called organic chemistry. By the end of the nineteenth century, scientists were able to synthesise hundreds of organic compounds.

Scientists like Oparin, Miller and Urey developed the theory of abiogenesis in 1950s. The formation of living forms from non-organic (non-living) matter is called abiogenesis. These scientists recreated the environment of a very young planet Earth in a laboratory. When gases containing inorganic elements, such as hydrogen, oxygen, nitrogen and carbon, were heated with water and energised by electrical discharge or by UV radiation, they formed small organic molecules. Today, the study of the chemistry of living things is called biochemistry. Organic chemistry is the chemistry of carbon compounds. Carbon is the main chemical element of all living things. The study of molecules that make up living cells is called molecular biology.

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