Chemistry

Chemistry: A Summary

• Chemistry is the scientific study of matter and its behavior, including the properties, composition, structure, and changes that occur during reactions.

• It is a physical science that occupies an intermediate position between physics and biology, and is sometimes referred to as the central science.

• The word chemistry comes from the modification of the word alchemy, which encompassed elements of chemistry, metallurgy, philosophy, astrology, astronomy, mysticism, and medicine.

• Chemistry is concerned with the study of elements, compounds, atoms, molecules, and ions, and their interactions, reactions, and transformations.

• A chemical reaction is a transformation of substances into one or more different substances, which occurs due to rearrangement of electrons in the chemical bonds between atoms.

• Energy and entropy considerations are important in almost all chemical studies, and chemical substances are classified in terms of their structure, phase, and chemical composition.

• Matter is anything that has rest mass and volume and is made up of particles, and can be either a pure chemical substance or a mixture of substances.

• The atom is the basic unit of chemistry, consisting of a nucleus made up of positively charged protons and uncharged neutrons, surrounded by negatively charged electrons.

• A chemical element is a pure substance composed of a single type of atom, characterized by its atomic number and mass number, and arranged in the periodic table by their atomic number.

• A compound is a pure chemical substance composed of more than one element, and a molecule is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties.

• Chemical substances can exist in several phases, such as solids, liquids, gases, and aqueous solutions, and are held together by chemical bonds, including covalent, ionic, and hydrogen bonds.

• Energy is an attribute of a substance as a consequence of its atomic, molecular or aggregate structure, and is involved in chemical transformations.Summary Title: Understanding the Fundamentals of Chemistry

• Chemical reactions involve the transfer of energy between the surroundings and reactants in the form of heat or light.

• Exergonic reactions result in a lower final energy state compared to the initial state, while endergonic reactions are the reverse.

• Activation energy is the energy barrier that reactants must overcome for a chemical reaction to occur.

• Free energy is a useful concept for predicting the feasibility and equilibrium state of a chemical reaction.

• Quantum mechanics determines the limited possible energy states of electrons, atoms, and molecules.

• The phase of a substance is determined by its energy and the energy of its surroundings.

• Heat energy is more easily transferred between substances than light or other forms of electronic energy.

• Spectroscopy is used to identify the composition of chemical substances and remote objects.

• Chemical reactions involve the formation or dissociation of molecules and the making or breaking of chemical bonds.

• Redox reactions involve changes in oxidation state and the transfer of electrons.

• Equilibrium describes the unchanging composition of a system of chemical substances even though they continue to react with each other.

• Chemistry has a long history, starting with alchemy, and has evolved with new discoveries and theories.A Brief History of Chemistry

• Greek atomism was purely philosophical in nature with little concern for empirical observations and no concern for chemical experiments.

• An early form of the idea of conservation of mass is the notion that "Nothing comes from nothing" in Ancient Greek philosophy.

• The Arabic works attributed to Jabir ibn Hayyan introduced a systematic classification of chemical substances.

• Boyle formulated Boyle's law, rejected the classical "four elements" and proposed a mechanistic alternative of atoms and chemical reactions that could be subject to rigorous experiment.

• Lavoisier established the principle of conservation of mass and developed a new system of chemical nomenclature used to this day.

• Dalton proposed the modern theory of atoms; that all substances are composed of indivisible 'atoms' of matter and that different atoms have varying atomic weights.

• The development of the electrochemical theory of chemical combinations occurred in the early 19th century.

• Prout first proposed ordering all the elements by their atomic weight.

• The year 2011 was declared by the United Nations as the International Year of Chemistry.

• Chemistry is typically divided into several major sub-disciplines.

• The chemical industry represents an important economic activity worldwide.

• The global top 50 chemical producers in 2013 had sales of US$980.5 billion with a profit margin of 10.3%.