From Wikipedia, the free encyclopedia.
Chemistry is the study of the atomic building blocks of nature, how they combine and their combinations which form the solids, liquids, and gases that make up most forms of matter. For the many different chemical elements and compounds, see:
- The Periodic table
- List of compounds
- Inorganic chemistry, including solid state chemistry, which studies the basic principles that are applied in mineralogy and materials science.
- Organic chemistry, which underlies biochemistry and polymer chemistry and is the study of carbon-containing molecules.
- Physical chemistry, which includes computational chemistry, quantum chemistry and surface chemistry.
- Analytical chemistry, the basis of environmental chemistry.
- Photochemistry, which through photosynthesis drives all of life.
The atomic theory is basic to chemistry. The theory states that all matter is composed of a set of very small units called atoms. One of the very first laws to be discovered leading to the establishment of chemistry as a science is the Law of Conservation of Mass. This law states there is no detectable change in the quantity of matter during an ordinary chemical reaction. (Modern physics now shows that it is actually energy that is conserved, and that energy and mass are related)
On a superficial level this means that if we start off with 10,000 atoms and proceed with many chemical reactions, we will still be left with exactly 10,000 atoms. The mass will be the same too if the energy gained or lost is accounted for. Chemistry studies the interactions of these atoms, sometimes alone but more often combined with (bonded to) other atoms to form ions and compounds/molecules. These atoms interact with other atoms (e.g. a wood fire is the combination of oxygen atoms from the air with the carbon and hydrogen atoms in the wood) and they may also interact with light (a photograph is formed from the changes that light causes to the chemicals on a film) and other types of radiation.
One surprisingly early finding was that these atoms almost always combine in definite ratios or proportions: silica sand is a structure where the ratio of silicon atoms to oxygen atoms is 1:2. We now know that there are exceptions to this law of definite proportions (integrated circuits are a good example).
Another key discovery in chemistry was that when a specific chemical reaction occurs, the amount of energy gained or lost will always be the same. This leads to the important concepts of equilibrium, thermodynamics, and kinetics.
Perhaps the most interesting theory, which could in principle describe all of chemistry is quantum mechanics. This theory is complex and non-intuitive. Thankfully, for the majority of the fields within chemistry, quantum mechanics is an irrelevence. Most chemical phenomena can be explained by simpler concepts which may be limited in scope, but are much easier to understand and apply.
College students typically study chemistry in the following "blocks": analytical chemistry, physical chemistry, organic chemistry, inorganic chemistry, polymer chemistry and biochemistry. Often, discoveries in chemistry are made by physicists, biologists, chemical engineers or pharmacists.
- Scientific method
- SI base unit
- Significant figures
- The Atom
- Periodic Table of Chemical elements
- Electron configuration
- Periodic Trends
- Elemental Groups: S-block, D-block, F-block, P-block
Chemicals and Interactions
States of Matter
Acids and Bases
Kinetics and Thermodynamics
History of Chemistry
- IUPAC Nomenclature Home Page, see especially the "Gold Book" containing definitions of standard chemical terms
- Material safety data sheets for a variety of chemicals
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