Chemistry

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.

Basics

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 Matter. The law states there is no detectable
change in the quantity of matter during an ordinary chemical reaction.
(Modern Physics now teaches that atoms and energy can be neither created nor
destroyed.) On a superficial level this means that if we start off with
10,001 atoms and proceed with many chemical reactions, we will be left with
10,001 atoms. Even if we started off with something green and gooey and
ended up with something black and hard there will still be the same number
of 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
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 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 change
is made, the amount of energy gained or lost will always be the same. This
leads to the important concepts of equilibrium, thermodynamics, and
kinetics. The most interesting theory describing all of chemistry is Quantum
Mechanics. This theory is complex, non-intuitive, and difficult to master.
Often, simpler concepts are used to predict the results of experiments.
These concepts (e.g. acid/base chemistry) are limited in scope, but 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.