Chemistry
Chemistry is a fundamental branch of physical science that investigates the properties of matter and the interactions between substances and energy. It examines everything that has mass and occupies space, forming the basis for understanding various scientific disciplines and everyday phenomena. The history of chemistry is rich, tracing back to ancient philosophers like Empedocles and Democritus, who laid the groundwork for concepts of elements and atoms. Over centuries, chemistry evolved through the contributions of notable figures such as Antoine Lavoisier, who established modern chemical principles, and Dmitri Mendeleev, who developed the Periodic Table of Elements.
The study of chemistry encompasses various branches, including analytical chemistry, which focuses on the composition of matter; organic chemistry, which deals with carbon-containing compounds; inorganic chemistry, studying non-organic materials; physical chemistry, exploring matter at a molecular level; and biochemistry, which looks at chemical processes within living organisms. Chemistry plays a crucial role in myriad applications—from developing pharmaceuticals and creating materials to understanding environmental impacts and enhancing agricultural practices. Its principles are integral to daily life, influencing cooking, cleaning, and technological advancements, reflecting its relevance across diverse cultures and communities.
Subject Terms
Chemistry
Chemistry is a branch of physical science that involves the study of the properties of matter, or anything that has mass, takes up space, and composes everything in life, and the way in which substances interact with other substances and energy. Many discoveries and advancements in the field of chemistry have occurred throughout time that have led to the formation of several principle branches and specific fields.
Chemistry plays a crucial role in day-to-day life. It is not only used in math and science classes or by the medical field; people also use chemistry in an array of other scenarios, from developing products to cooking and even cleaning.
History of Chemistry
Around 450 BCE, Greek philosopher Empedocles developed the theory that all matter consists of four elemental substances: earth, air, fire, and water. Empedocles's theory was widely accepted throughout Europe for centuries to come.
Greek philosopher Democritus proposed his own theory of matter around 420 BCE. He stated that all matter is made of eternal, indivisible, indestructible, and infinitely small substances. He argued that these substances stick together to form objects. Democritus's theory marked the beginnings of the atom, or the smallest unit of matter.
In the fourth century BCE, Greek philosopher Aristotle developed a theory that was based on the theories of both Empedocles and Democritus. Aristotle asserted that Empedocles's four elements, along with Democritus's atoms, form substances. Furthermore, he proposed that two pairs of alternatives determined matter. These pairs were hot and cold and moist and dry. This meant that the possible combinations of elements were earth that was cold and dry; air that was hot and moist; fire that was hot and dry; and water that was cold and moist. Aristotle claimed that a variable balance existed between these characteristics that created the atoms of objects.
Alexandria, Egypt, produced the first alchemists and experimental chemists in the third century BCE. These chemists worked with precious metals, melting them, changing their color, and mixing alloys. They typically sought to turn base metals into gold. Alchemists believed this was possible because of Aristotle's theory of variable balance. If they could change the balance of a certain metal, they might be able to turn the metal into gold. Between the eighth and tenth centuries CE, alchemists in Asia—specifically in Baghdad and China—advanced the field of chemistry. In Baghdad, alchemists pursued synthesized gold, identified numerous chemical substances, and made advancements in distillation techniques. In China, alchemists sought an elixir that would offer eternal life. These alchemists were Daoists, and they would eventually discover gunpowder in the eleventh century. Daoists followed a Chinese mystical philosophy called Daoism, which taught simple living and harmony with nature.
Jābir ibn Hayyān, a Muslim scientist, studied materials using scientific methods in the eighth century CE. Regarded as the "father of chemistry," Jābir identified various chemical methods and invented a device called an alembic, which was used to distill and study acids. He was also known for creating a chemical classification system, which included three categories—spirits, metals, and nonmalleable substances. Spirits are materials that vaporize when heated. This means the material moves into a gaseous state when heated. Metals include lead, iron, copper, etc. Nonmalleable substances are materials that could be turned into powder.
Many other advancements in chemistry followed. In the late seventeenth century, German chemist Johann Joachim Becher introduced the phlogiston theory, which German chemist Georg Ernst Stahl further developed. Becher believed that a material released a certain substance when it underwent the natural processes of either burning or rusting. The substance, which was thought to have no color, odor, taste, or weight, was later given the name phlogiston by Stahl. The theory was widely accepted by scientists of the time. However, French chemist Antoine Lavoisier disproved the theory in the eighteenth century.
The seventeenth and eighteenth centuries also brought some notable books to the field of chemistry. Anglo-Irish philosopher Robert Boyle published the first chemistry textbook, The Sceptical Chymist, in the seventeenth century. Boyle studied gases and noted many of his findings in the book. Lavoisier, who made significant contributions to chemistry, including helping to develop the metric system, discovering the Law of Conservation of Mass, and developing rules for naming chemical compounds, published the first modern chemistry textbook, Elementary Treatise of Chemistry, in the eighteenth century.
However, one of the most important developments in chemistry was the development of the Periodic Table of the Elements in the nineteenth century. Russian chemist Dmitri Mendeleev developed the table, which included the sixty-three known elements of the time and their properties. After the discovery of additional elements, the table was updated to include these.
The nineteenth and twentieth centuries also brought several discoveries related to the atom. Italian scientist Amedeo Avogadro identified a difference between the atom and the molecule. A molecule is a group of two or more atoms. The difference between the two is that a molecule can be broken down, but an atom cannot. Avogadro also determined the number of molecules in pure substances, which would eventually become known as Avogadro constant (or Avogadro's law). Additionally, British physicist Ernest Rutherford determined that atoms contain positively and negatively charged particles, and Niels Bohr, a Danish physicist, developed an atomic model that remained in use into the twenty-first century to demonstrate chemical bonding. In 1896, French physicist Henri Becquerel discovered radioactivity and subsequently shared a Nobel Prize with French chemists Marie and Pierre Curie, who also contributed to the discovery of radioactivity.
Other notable contributors to the field of chemistry during this time include English chemist Joseph Priestley, who isolated oxygen and also discovered seven other gases; French chemist Joseph Proust, who discovered the Law of Definite Proportions regarding chemical compounds; English meteorologist John Dalton, who worked with water vapor and particles in gases; and English physicist James Chadwick, who discovered the neutron and later won a Nobel Prize for his work. The field of chemistry continued to evolve into the twenty-first century, playing a role in activities and innovations in a wide variety of areas, from agriculture to energy, medicine, and technology.
Matter
Understanding matter is crucial to grasping the study of chemistry. Matter is something that has mass and occupies space. The five states of matter (also called phases of matter) include solids, liquids, gases, plasma, and Bose-Einstein condensate. A solid has a definite shape and volume. Like all states of matter, solids contain particles. The particles in a solid are crammed together, which limits their movement. A solid, therefore, has low kinetic energy. Kinetic energy is the energy of motion. An object's kinetic energy is dependent on its mass and speed. The atoms in a solid have electrons that move, but the atoms themselves are set in place and do not vibrate much. If a solid was placed in a container, it would not conform, meaning it would not change shape to fit into the shape of the container. Furthermore, a solid cannot be compressed to a smaller volume. Examples of solids include ice, wood, and steel.
A liquid has an indefinite shape but a definite volume. Liquids have particles that are not as tightly crammed together as solids. Therefore, liquids have higher kinetic energy than solids. Liquid particles are able to move around one another. Unlike a solid, a liquid will conform to the container in which it is placed. If an object were placed into a liquid, the object would displace the liquid particles. As with solids, liquids are not able to be compressed to a smaller volume. Water, blood, and gasoline are examples of liquids.
A gas has an indefinite shape and volume. The particles of a gas have a large amount of space between them, so they move freely. Gases have higher kinetic energy than both solids and liquids. Gas particles are able to disperse indefinitely if the gas is unconfined. If a gas is placed in a container, the gas will completely fill the container. Examples of gases are water vapor, hydrogen, and propane.
Plasma contains particles that are highly charged and have very high kinetic energy. Although plasma is uncommon on Earth, it is prevalent elsewhere in the universe. For example, stars are balls of plasma. On Earth, certain gases can be ionized to the plasma state by using electricity. An example of this is a neon sign.
Bose-Einstein condensate (BEC) is a state of matter that was created by scientists Eric Cornell and Carl Wieman in 1995. The pair took a sample of the element rubidium and cooled it to a very low temperature. The molecules in the rubidium slowed down to the point of almost stopping completely. The rubidium, therefore, had very low kinetic energy. The result was that the atoms clustered together, forming one "super atom." BEC eventually was used in the study of quantum mechanics and black holes.
Matter is capable of transitioning from one state to another. A solid can melt into a liquid or change into a gas. A liquid can freeze into a solid or transform into a gas. A gas can change into a solid, liquid, or plasma. Only certain elements, such as rubidium, can transform into a BEC. All of these transitions are dependent upon temperature and pressure.
Branches of Chemistry
Five principle branches of chemistry exist: analytical, physical, organic, inorganic, and biochemistry. Analytical chemistry is the study of the composition and structure of matter. Analytical chemists often study the quality and safety of food, water, and pharmaceuticals, or medications; assist doctors in diagnosing diseases; evaluate commerce and trade; ensure compliance with regulations such as rules involving the environment; and assist in legal procedures.
Physical chemistry encompasses the study of matter at the molecular and atomic level. It also involves the study of chemical reactions. Physical chemists focus on the physical characteristics of materials, as they analyze materials, develop methods for testing materials, and determine materials' use.
Organic chemistry involves the study of compounds that contain carbon, especially those compounds produced by living organisms. It is often used to develop and study foods, plastics, pharmaceuticals, cosmetics, and explosives. Organic chemists typically develop new compounds and strive to improve the ways in which existing compounds are synthesized.
Inorganic chemistry is the study of inorganic compounds such as metals and minerals. This branch of chemistry is used in many industries, including mining, plastics, and microchips. Inorganic chemists often work with compounds at the molecular level.
Biochemistry entails the study of substances in living organisms. It is a combination of biology and the branches of physical, organic, and inorganic chemistry. Biochemistry encompasses several other sciences, including biophysical chemistry, bioorganic chemistry, bioinorganic chemistry, molecular biology, immunochemistry, and neurochemistry. Biochemists generally focus on the structure and functions of living organisms and how to control them.
Many other fields of study related to chemistry exist. Examples include environmental chemistry, food chemistry, agricultural chemistry, geochemistry, and chemical engineering.
Bibliography
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