is the Science
; The branch of the natural sciences dealing with the
Glossary of Chemistry Terms
Chemistry Stack Exchange
is a question and answer site for scientists.
is a scientist trained in the study of chemistry.
Chemists study the composition of matter
and its properties. Chemists
carefully describe the properties they study in terms of quantities,
with detail on the level of molecules and their component atoms.
Chemists carefully measure substance proportions, reaction rates, and
other chemical properties. Drug
is a form of matter that has constant chemical
composition and characteristic properties. It cannot be separated into
components by physical separation methods, i.e., without breaking
chemical bonds. Chemical substances can be chemical elements, chemical
compounds, ions or alloys.
is any of a material's properties that becomes
evident during, or after, a chemical reaction; that is, any quality that
can be established only by changing a substance's chemical identity.
Simply speaking, chemical properties cannot be determined just by
viewing or touching the substance; the substance's internal structure
must be affected greatly for its chemical properties to be investigated.
When a substance goes under a chemical reaction, the properties will
change drastically, resulting in chemical change. However, a catalytic
property would also be a chemical property.
refers to the
arrangement, type, and ratio of atoms in molecules of chemical
substances. Chemical composition varies when chemicals are added or
subtracted from a substance, when the ratio of substances changes, or
when other chemical changes occur in chemicals.
is a material system made up of two or more different substances which
are mixed but are not combined chemically. A mixture refers to the
physical combination of two or more substances in which the identities
are retained and are mixed in the form of solutions, suspensions, and
is a process that leads to the
of one set of
chemical substances to another. Classically, chemical reactions
encompass changes that only involve the positions of
forming and breaking of chemical bonds between atoms, with no change to
the nuclei (no change to the elements present), and can often be
described by a chemical equation.
kind of action that occurs as two or more objects have an
is a sub-discipline
of chemistry that involves the chemical reactions of unstable and
radioactive elements where both electronic and
refers to the similarity of chemical
elements, molecules or chemical compounds with respect to either
structural or functional qualities, i.e. the effect that the chemical
compound has on reaction partners in inorganic or biological settings.
Biological effects and thus also similarity of effects are usually
quantified using the biological activity of a compound. In general
terms, function can be related to the chemical activity of compounds
chemical substance to undergo a transformation through a chemical
reaction to transform other chemical substances. Examples include
batteries, food, gasoline, and more. Breaking or making of chemical
bonds involves Energy
, which may be either
absorbed or evolved from a chemical system.
is a chemistry subdiscipline involving the
scientific study of the structure, properties, and reactions of organic
compounds and organic materials, i.e., matter in its various forms that
contain carbon atoms. Study of structure includes many physical and
chemical methods to determine the chemical composition and the chemical
constitution of organic compounds and materials. Study of properties
includes both physical properties and chemical properties, and uses
similar methods as well as methods to evaluate chemical reactivity, with
the aim to understand the behavior of the organic matter in its pure
form (when possible), but also in solutions, mixtures, and fabricated
forms. The study of organic reactions includes probing their scope
through use in preparation of target compounds (e.g., natural products,
drugs, polymers, etc.) by chemical synthesis, as well as the focused
study of the reactivities of individual organic molecules, both in the
laboratory and via theoretical (in silico) study.
Organic Materials Database
deals with the synthesis and behavior of inorganic and organometallic
compounds. This field covers all chemical compounds except the myriad
organic compounds (carbon based compounds, usually containing C-H
bonds), which are the subjects of organic chemistry. The distinction
between the two disciplines is far from absolute, as there is much
overlap in the subdiscipline of organometallic chemistry. It has
applications in every aspect of the chemical industry, including
catalysis, materials science, pigments, surfactants, coatings,
medications, fuels, and agriculture.
is the study of macroscopic,
, subatomic, and particulate phenomena in chemical systems in
terms of the principles, practices and concepts of physics such as
motion, energy, force
, quantum chemistry,
statistical mechanics, analytical dynamics and chemical equilibrium.
is a subfield of study within physical
chemistry concerned with the interaction of light with electrochemical
systems. It is an active domain of investigation. One of the pioneers of
this field of
was the German electrochemist Heinz Gerischer. The
interest in this domain is high in the context of development of
renewable energy conversion and
sometimes called biological chemistry, is the study of chemical
processes within and relating to living organisms. By controlling
information flow through biochemical signaling and the flow of chemical
energy through metabolism, biochemical processes give rise to the
complexity of life. Over the last decades of the 20th century,
biochemistry has become so successful at explaining living processes
that now almost all areas of the life sciences from botany to medicine
to genetics are engaged in biochemical research. Today, the main focus
of pure biochemistry is on understanding how biological molecules give
rise to the processes that occur within living cells, which in turn
relates greatly to the study and understanding of tissues, organs, and
whole organisms-that is, all of biology.
scientists that are trained in biochemistry.
studies and uses instruments and methods used to separate, identify, and
quantify matter. In practice separation, identification or
quantification may constitute the entire analysis or be combined with
another method. Separation isolates analytes. Qualitative analysis
identifies analytes, while quantitative analysis determines the
numerical amount or concentration.
is the science that uses the tools and
principles of chemistry to explain the mechanisms behind major
geological systems such as the Earth's crust and its oceans. The realm
of geochemistry extends beyond the Earth, encompassing the entire Solar
System and has made important contributions to the understanding of a
number of processes including mantle convection, the formation of
planets and the origins of granite and basalt.
are disciplines at the intersection of
chemistry, especially synthetic organic chemistry, and pharmacology and
various other biological specialties, where they are involved with
design, chemical synthesis and development for market of pharmaceutical
agents, or bio-active molecules (drugs).
is a branch of chemistry that uses
computer simulation to assist in solving chemical problems. It uses
methods of theoretical chemistry, incorporated into efficient computer
programs, to calculate the structures and properties of molecules and
solids. It is necessary because, apart from relatively recent results
concerning the hydrogen molecular ion (dihydrogen cation, see references
therein for more details), the quantum many-body problem cannot be
solved analytically, much less in closed form. While computational
results normally complement the information obtained by chemical
experiments, it can in some cases predict hitherto unobserved chemical
phenomena. It is widely used in the design of new drugs and materials.
is an area of chemistry and chemical
engineering focused on the designing of products and processes that
minimize the use and generation of hazardous substances. Whereas
environmental chemistry focuses on the effects of polluting chemicals on
nature, green chemistry focuses on technological approaches to
preventing pollution and reducing consumption of nonrenewable resources.
Also called sustainable chemistry.
is a geometric property of some
molecules and ions. A chiral molecule/ion is non-superposable on its
mirror image. The presence of an asymmetric carbon center is one of
several structural features that induce chirality in organic and
are macromolecular biological catalysts. Enzymes
accelerate, or catalyze, chemical reactions. The molecules at the
beginning of the process upon which enzymes may act are called substrates
and the enzyme converts these into different molecules, called products.
Almost all metabolic processes in the cell need enzymes in order to occur
at rates fast enough to sustain life. The set of enzymes made in a cell
determines which metabolic pathways occur in that cell. The study of
enzymes is called enzymology.
is the process whereby biological cells
generate new proteins; it is balanced by the loss of cellular proteins
via degradation or export. Translation, the assembly of amino acids by
ribosomes, is an essential part of the biosynthetic pathway, along with
generation of messenger RNA
aminoacylation of transfer RNA (tRNA), co-translational transport, and
post-translational modification. Protein biosynthesis is strictly
regulated at multiple steps. They are principally during transcription
(phenomena of RNA synthesis from DNA template) and translation (phenomena
of amino acid assembly from RNA).
are chemical products derived from petroleum.
Some chemical compounds made from petroleum are also obtained from other
fossil fuels, such as coal or natural gas, or renewable sources such as
corn or sugar cane.
Order of Reaction
in chemical kinetics, the order of
reaction with respect to a given substance (such as reactant, catalyst or
product) is defined as the index, or exponent, to which its concentration
term in the rate equation is raised.
also known as reaction kinetics, is the study of rates of
chemical processes. Chemical kinetics includes investigations of how
different experimental conditions can influence the speed of a chemical
reaction and yield information about the reaction's mechanism and
transition states, as well as the construction of mathematical models
that can describe the characteristics of a chemical reaction.
is the increase in the rate of a chemical reaction due to the
participation of an additional substance called a catalyst. In most
cases, reactions occur faster with a catalyst because they require less
activation energy. Furthermore, since they are not consumed in the
catalyzed reaction, catalysts can continue to act repeatedly. Often only
tiny amounts are required in principle.
. A single chemical reaction is said to have
undergone autocatalysis, or be autocatalytic, if one of the reaction
products is also a reactant and therefore a catalyst in the same or a
coupled reaction. The reaction is called an autocatalytic reaction.
is a water soluble mixture of different dyes extracted from lichens. It
is often absorbed onto filter paper to produce one of the oldest forms of
pH indicator, used to test materials for acidity.
of a chemical compound is a graphic
representation of the molecular structure, showing how the atoms are
arranged. The chemical bonding within the molecule is also shown, either
explicitly or implicitly. Unlike chemical formulas, which have a limited
number of symbols and are capable of only limited descriptive power,
structural formulas provide a complete geometric representation of the
molecular structure. For example, many chemical compounds exist in
different isomeric forms, which have different enantiomeric structures
but the same chemical formula. A structural formula is able to indicate
arrangements of atoms in three dimensional space in a way that a chemical
formula may not be able to do.
Chemical equations usually do not come already
balanced. ... Therefore, we must finish our chemical reaction with as
many atoms of each element as when we started. Example #1: Balance the
following equation: H2 + O2 ---> H2O. It is an unbalanced equation
(sometimes also called a skeleton equation). A skeleton equation is just
a way of using the formulas to indicate the chemicals that were involved
in the chemical reaction. "Mg + O2 MgO." This skeleton equation shows
that magnesium reacts with oxygen to form magnesium oxide.
is the process that creates new atomic
nuclei from pre-existing nucleons, primarily protons and neutrons.
is the thermal motion of all (liquid or
gas) particles at temperatures above absolute zero. The rate of this
movement is a function of temperature, viscosity of the fluid and the
size (mass) of the particles. Diffusion explains the net flux of
molecules from a region of higher concentration to one of lower
concentration. Once the concentrations are equal the molecules continue
to move, but since there is no concentration gradient the process of
molecular diffusion has ceased and is instead governed by the process of
self-diffusion, originating from the random motion of the molecules. The
result of diffusion is a gradual mixing of material such that the
distribution of molecules is uniform. Since the molecules are still in
motion, but an equilibrium has been established, the end result of
molecular diffusion is called a "dynamic equilibrium". In a phase with
uniform temperature, absent external net forces acting on the particles,
the diffusion process will eventually result in complete mixing.
is the net movement of molecules or atoms from a
region of high concentration (or high chemical potential) to a region of
low concentration (or low chemical potential). This is also referred to
as the movement of a substance down a concentration gradient. A gradient
is the change in the value of a quantity (e.g., concentration, pressure,
temperature) with the change in another variable (usually distance). For
example, a change in concentration over a distance is called a
concentration gradient, a change in pressure over a distance is called a
pressure gradient, and a change in temperature over a distance is a
called a temperature gradient.
is a property of a system or of a
material itself or within. It is independent of how much of the material
is present and is independent of the form of the material, e.g., one
large piece or a collection of small particles. Intrinsic properties are
dependent mainly on the chemical composition or structure of the
is the determination of the absolute
or relative abundance (often expressed as a concentration) of one,
several or all particular substance(s) present in a sample.
is a protein molecule that receives chemical
signals from outside a cell. When such chemical signals bind to a
receptor, they cause some form of cellular/tissue response, e.g. a change
in the electrical activity of a cell. In this sense, a receptor is a
protein-molecule that recognizes and responds to endogenous chemical
signals, e.g. an acetylcholine receptor recognizes and responds to its
endogenous ligand, acetylcholine. However, sometimes in pharmacology, the
term is also used to include other proteins that are drug targets, such
as enzymes, transporters and ion channels.
are substances that, in aqueous solution, are slippery
to the touch, taste astringent, change the color of indicators (e.g.,
turn red litmus paper blue), react with acids to form salts, promote
certain chemical reactions (base catalysis), accept protons from any
proton donor, and/or contain completely or partially displaceable OH−
ions. Examples of bases are the hydroxides of the alkali metals and
alkaline earth metals (NaOH, Ca(OH)2, etc.).
Periodic Table of Elements
Periodic Table of Elements
Wiki Periodic Table
(wiki periodic table)
Earth & Sky Chart
means "single atom
." It is usually applied to gases: a monatomic gas is
one in which atoms are not bound to each other. All chemical elements
will be monatomic in the gas phase at sufficiently high temperatures. The
thermodynamic behavior of monatomic gas is extremely simple when compared
to polyatomic gases because it is free of any rotational or vibrational
are all odorless, colorless, monatomic gases with
very low chemical reactivity. The six noble gases that occur naturally
are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the
radioactive radon (Rn). Oganesson (Og) is predicted to be a noble gas as
well, but its chemistry has not yet been investigated.
A Tour of
the Periodic Table
Uus element 117)
(# of Protons)
Relative Atomic Mass
is a dimensionless physical quantity,
the ratio of the average mass
of atoms of an element (from a single given
sample or source) to 1⁄12 of the mass of an atom of carbon-12
the unified atomic mass unit).
is the distribution of electrons
an atom or molecule (or other physical structure) in atomic or molecular
is a way of describing delocalized electrons
within certain molecules or polyatomic ions where the bonding cannot be
expressed by one single Lewis structure. A molecule or ion with such
delocalized electrons is represented by several contributing structures
(also called resonance structures or canonical structures).
Rare Earth Minerals
Mineral or Element?
is any naturally occurring, inorganic substance, often additionally
characterized by an exact crystal structure. A solid homogeneous
inorganic substances occurring in nature having a definite chemical
composition. Its chemical structure can be exact, or can vary within
, the smallest piece that we can
split matter into (except for subatomic particles and other things.
Elements often are stacked together with other elements to form minerals.
Native elements that occur naturally are also considered minerals.
Native Element Minerals
are those elements that occur in nature in
uncombined form with a distinct mineral structure. The elemental class
includes metals and intermetallic elements, naturally occurring alloys,
semi-metals and non-metals. The Nickel–Strunz classification system also
includes the naturally occurring phosphides, silicides, nitrides and
are a composed of
one or more minerals.
is formed when two or more
join together chemically.
is molecule that is present in living
large macromolecules such as proteins
, lipids, and
nucleic acids, as well as small molecules such as primary metabolites,
secondary metabolites, and natural products. A more general name for
this class of material is biological materials. Biomolecules are usually
endogenous but may also be exogenous. For example, pharmaceutical drugs
may be natural products or semisynthetic (biopharmaceuticals) or they
may be totally synthetic.
is an emerging field of study concerned with
the design and testing of molecular properties, behavior and interactions
in order to assemble better materials, systems, and processes for
specific functions. This approach, in which observable properties of a
macroscopic system are influenced by direct alteration of a molecular
structure, falls into the broader category of “bottom-up” design.
is a variation in a single nucleotide
that occurs at a specific position in the genome, where each variation is
present to some appreciable degree within a population.
organic molecules that serve as the monomers, or subunits, of nucleic
acids like DNA and RNA
. The building
blocks of nucleic acids, nucleotides are composed of a nitrogenous base,
a five-carbon sugar (ribose or deoxyribose), and at least one phosphate
group. Thus a nucleoside plus a phosphate group yields a nucleotide.
is a molecule
that may bind chemically or supramolecularly to other molecules to form a
is a polymer whose monomer repeat units are
held together by noncovalent bonds. Non-covalent forces that hold
supramolecular polymers together include coordination, π-π interactions,
and hydrogen bonding. Supramolecular
polymers can have physical
properties similar to plastic materials, while having better
processability and better recycling and self-healing properties, thanks
to their reversible transition from monomer to polymer structure.
concerns the molecular basis of biological
activity between biomolecules in the various systems of a cell, including
the interactions between DNA, RNA, and proteins and their biosynthesis,
as well as the regulation of these interactions
Automated Small-Molecule Synthesis
are molecules composed of only two atoms, of the same or
different chemical elements.
is a molecule that may bind chemically or supramolecularly to other
molecules to form a (supramolecular) polymer.
is a lasting attraction between atoms that
enables the formation of chemical compounds. The bond may result from the
electrostatic force of attraction between atoms with opposite charges, or
through the sharing of electrons as in the covalent bonds. The strength
of chemical bonds varies considerably; there are "strong bonds" or
"primary bond" such as metallic, covalent or ionic bonds and "weak bonds"
or "secondary bond" such as Dipole-dipole interaction, the London
dispersion force and hydrogen bonding.
also called a molecular bond, is a chemical bond that involves the
sharing of electron pairs between atoms. These electron pairs are known
as shared pairs or bonding pairs, and the stable balance of attractive
and repulsive forces between atoms, when they share electrons, is known
as covalent bonding. For many molecules, the sharing of electrons allows
each atom to attain the equivalent of a full outer shell, corresponding
to a stable electronic configuration.
is a geometric property of some molecules and ions. A chiral molecule/ion
is non-superposable on its mirror image. The presence of an asymmetric
carbon center is one of several structural features that induce chirality
in organic and inorganic molecules.
Water in Space
is a molecule that contains at least two different
. Every combination of atoms is a molecule, but not
all molecules are compounds. Hydrogen gas (H2) is a molecule,
but not a compound because it is made of only one element.
(H2O) can be called a molecule or a compound because it is made
of hydrogen (H) and oxygen (O) atoms.
is virtually any chemical compound that contains carbon
, although a
consensus definition remains elusive and likely arbitrary. Organic
compounds are rare terrestrially, but of central importance because all
known life is based on organic compounds. The most basic petrochemicals
are considered the building blocks of organic chemistry.
There are now more than ten million
known by chemists.
biologically important organic compounds containing amine (-NH2) and
carboxyl (-COOH) functional groups, along with a side-chain (R group)
specific to each amino acid. The key elements of an amino acid are
carbon, hydrogen, oxygen, and nitrogen, though other elements are found
in the side-chains of certain amino acids. About 500 amino acids are
known (though only 20 appear in the genetic code) and can be classified
in many ways. Nine proteinogenic amino acids are called "essential" for
humans because they cannot be created from other compounds by the human
body and so must be taken in as food. Others may be conditionally
essential for certain ages or medical conditions. Essential amino acids
may also differ between species. Because of their biological
significance, amino acids are important in nutrition and are commonly
used in nutritional supplements, fertilizers, and food technology.
Industrial uses include the production of drugs, biodegradable plastics,
and chiral catalysts.
85% of all known compounds?
can make around 1.7 million different
Carbon-12 is the more abundant carbon of the two stable
isotopes, amounting to 98.93% of the element carbon; its abundance is due
to the triple-alpha process by which it is created in
stars. Carbon-12 is of particular importance
in its use as the standard from which atomic masses of all nuclides are
measured: its mass number is 12 by definition and contains
6 protons, 6
neutrons and 6 electrons.
Carbon is a chemical
element with symbol C and atomic number 6. It is nonmetallic and
tetravalent—making four electrons available to form covalent chemical
bonds. Three isotopes occur naturally, 12C and 13C being stable, while
14C is a radioactive isotope, decaying with a half-life of about 5,730
years. Carbon is one of the few elements known since
Chem 4 Kids
refers to a combination of two or more entities
that together form something new; alternately, it refers to the creating
of something by artificial means.
is a thermochemical decomposition of organic
material at elevated temperatures in the absence of oxygen (or any
halogen). It involves the simultaneous change of chemical composition and
physical phase, and is irreversible.
is a sub-discipline of analytical chemistry
covering the quantitative measurement of xenobiotics (drugs and their
metabolites, and biological molecules in unnatural locations or
concentrations) and biotics (macromolecules, proteins, DNA, large
molecule drugs, metabolites) in biological systems.
is the branch of physics
which deals with the
Thermodynamics is the branch of
and their relation to
energy and work. It states that the behavior of these quantities is
governed by the four laws of thermodynamics, irrespective of the
composition or specific properties of the material or system in
question. The laws of thermodynamics are explained in terms of
microscopic constituents by statistical mechanics. Thermodynamics
applies to a wide variety of topics in science and engineering,
especially physical chemistry, chemical engineering and mechanical
Laws of Thermodynamics
define fundamental physical
quantities (temperature, energy, and entropy) that characterize
thermodynamic systems at thermal equilibrium. The laws describe how
these quantities behave under various circumstances, and forbid certain
phenomena (such as perpetual motion
Second Law of Thermodynamics
"what goes up must come down"
Second Law of Thermodynamics
dictates that everything ages, Death
decays, and states that the total entropy
isolated system always increases over time, or remains constant in ideal
cases where the system is in a steady state or undergoing a reversible
process. The increase in entropy accounts for the irreversibility of
natural processes, and the asymmetry between future and past.
Historically, the second law was an empirical finding that was accepted
as an axiom of thermodynamic theory. Statistical thermodynamics,
classical or quantum, explains the microscopic origin of the law. The
second law has been expressed in many ways. There is an upper limit to
the efficiency of conversion of heat to work
in a heat engine
is a branch of science concerned with heat and
temperature and their relation to energy
is an axiomatic concept of thermodynamics.
It is an internal state of a single thermodynamic system, or a relation
between several thermodynamic systems connected by more or less
permeable or impermeable walls. In thermodynamic equilibrium there are
no net macroscopic flows of matter or of energy, either within a system
or between systems. In a system in its own state of internal
, no macroscopic
change occurs. Systems in mutual thermodynamic equilibrium are
simultaneously in mutual thermal, mechanical, chemical, and radiative
equilibria. Systems can be in one kind of mutual equilibrium, though not
in others. In thermodynamic equilibrium, all kinds of equilibrium hold
at once and indefinitely, until disturbed by a thermodynamic operation.
In a macroscopic equilibrium, almost or perfectly exactly balanced
microscopic exchanges occur; this is the physical explanation of the
notion of macroscopic equilibrium.
deals with physical systems that are
not in thermodynamic equilibrium but can adequately be described in terms
of variables (non-equilibrium state variables) that represent an
extrapolation of the variables used to specify the system in
thermodynamic equilibrium. Non-equilibrium thermodynamics is concerned
with transport processes and with the rates of chemical reactions. It
relies on what may be thought of as more or less nearness to
thermodynamic equilibrium. Non-equilibrium thermodynamics is a work in
progress, not an established edifice. This article will try to sketch
some approaches to it and some concepts important for it. Almost all
are not in thermodynamic
equilibrium; for they are changing or can be triggered to change over
time, and are continuously and discontinuously subject to flux of
to and from other systems and to chemical reactions. Some systems and
processes are, however, in a useful sense, near enough to thermodynamic
equilibrium to allow description with useful accuracy by currently known
non-equilibrium thermodynamics. Nevertheless, many natural systems and
processes will always remain far beyond the scope of non-equilibrium
thermodynamic methods. This is because of the very small size of atoms,
as compared with macroscopic systems.
is the material and radiative content of a
macroscopic volume in space, that can be adequately described by
thermodynamic state variables such as temperature, entropy, internal
energy and pressure.
is the study of the interrelation of
heat and work with chemical reactions or with physical changes of state
within the confines of the laws of thermodynamics.
an organic compound with the chemical formula CO(NH2)2. Urea serves an
important role in the metabolism of nitrogen-containing compounds by
animals, and is the main nitrogen-containing substance in the urine of
Thermodynamics of Computation
Chemical Process Modeling
is a computer modeling technique
used in chemical engineering process design. It typically involves using
purpose-built software to define a system of interconnected components,
which are then solved so that the steady-state or dynamic behavior of
the system can be predicted. The system components and connections are
represented as a Process Flow diagram. Simulations can be as simple as
the mixing of two substances in a tank, or as complex as an entire
of a substance is the temperature and pressure
at which the three phases (gas, liquid, and solid) of that substance
coexist in thermodynamic equilibrium.
is a column of rising
in the lower
altitudes of Earth's atmosphere
Thermals are created by the uneven heating of Earth's surface from
, and are an example of
. The Sun warms the ground, which in turn
warms the air directly above it. Dark earth, urban areas, and roadways
are good sources of thermals
objective comparative measurement of hot or cold. It is measured by a
thermometer. Several scales and units exist for measuring temperature,
the most common being Celsius (denoted °C; formerly called centigrade),
Fahrenheit (denoted °F), and, especially in science, Kelvin (denoted K).
The coldest theoretical temperature is absolute zero, at which the
thermal motion of atoms and molecules reaches its minimum – classically,
this would be a state of motionlessness, but quantum uncertainty dictates
that the particles still possess a finite zero-point energy. Absolute
zero is denoted as 0 K on the Kelvin scale, −273.15 °C on the Celsius
scale, and −459.67 °F on the Fahrenheit scale. The kinetic theory offers
a valuable but limited account of the behavior of the materials of
macroscopic bodies, especially of fluids. It indicates the absolute
temperature as proportional to the average kinetic energy of the random
microscopic motions of those of their constituent microscopic particles,
such as electrons, atoms, and molecules, that move freely within the
material. Thermal vibration of a segment of protein alpha helix: The
amplitude of the vibrations increases with temperature. Temperature is
important in all fields of natural science including physics, geology,
chemistry, atmospheric sciences, medicine and biology as well as most
aspects of daily life.
is the lower limit of the thermodynamic temperature scale, a state at
which the enthalpy and entropy of a cooled ideal gas reaches its minimum
value, taken as 0. The theoretical temperature is determined by
extrapolating the ideal gas law; by international agreement, absolute
zero is taken as −273.15° on the Celsius scale (International System of
Units), which equates to −459.67° on the Fahrenheit scale (United States
customary units or Imperial units). The corresponding Kelvin and Rankine
temperature scales set their zero points at absolute zero by definition.
is a unit of measure for temperature based upon an absolute scale. It is
one of the seven base units in the International System of Units (SI) and
is assigned the unit symbol K. The Kelvin scale is an absolute,
thermodynamic temperature scale using as its null point absolute zero,
the temperature at which all thermal motion ceases in the classical
description of thermodynamics.Body
(0C = 32F, 27C = 80F, for every 10 Degrees F increase is equal
to around a 5C increase)
is a thermodynamic quantity representing the
amount of energy
that is no longer available for
doing mechanical work
available for useful work in a system, and
suggest greater energy
. "entropy increases as matter and energy
in the universe degrade to an ultimate state of
in statistical thermodynamics, entropy (usual symbol
S) is a measure of the number of microscopic configurations Ω that
correspond to a thermodynamic system in a state specified by certain
macroscopic variables. Specifically, assuming that each of the
microscopic configurations is equally probable, the entropy of the
system is the natural logarithm of that number of configurations,
multiplied by the Boltzmann constant kB (which provides consistency with
the original thermodynamic concept of entropy discussed below, and gives
entropy the dimension of energy divided by temperature)
Entropy and Life
Entropy and Life
Thermodynamic free energy
is the amount of
that a thermodynamic
system can perform.
Entropy (order disorder)
is associated with the
amount of order, disorder, or
in a thermodynamic system.
Entropy (information theory
) systems are modeled by a transmitter,
channel, and receiver. The transmitter produces messages that are sent
through the channel. The channel modifies the message in some way. The
receiver attempts to infer which message was sent.
is a force resulting from the entire system's
tendency to increase its entropy, rather than from a
particular underlying microscopic force. For instance, the internal
energy of an ideal gas depends only on its temperature, and not on the
volume of its containing box, so it is not an energy effect that tends to
increase the volume of the box as gas pressure does. This implies that
the pressure of an ideal gas has an entropic origin. What is the origin
of such an entropic force? The most general answer is that the effect of
thermal fluctuations tends to bring a thermodynamic system toward a
macroscopic state that corresponds to a maximum in the number of
microscopic states (or micro-states) that are compatible with this
macroscopic state. In other words, thermal fluctuations tend to bring a
system toward its macroscopic state of maximum entropy.
is a measurement of energy in a thermodynamic system. It is the
thermodynamic quantity equivalent to the total heat content of a system.
It is equal to the internal energy of the system plus the product of
pressure and volume. More technically, it includes the internal energy,
which is the energy required to create a system, and the amount of energy
required to make room for it by displacing its environment and
establishing its volume and pressure.
Janet Iwasa: How 3D Animations help Scientists Visualize what we
is a branch of biology, chemistry, and medicine
(more specifically pharmacology
concerned with the study of the adverse effects of chemicals on living
is the metabolic breakdown of drugs by
is a branch of pharmacology dedicated to
determining the fate of substances administered to a living organism.
is the branch of medicine and biology concerned with the study of drug
action, where a drug can be broadly defined as any man-made, natural, or
endogenous (from within body) molecule which exerts a biochemical and/or
physiological effect on the cell, tissue, organ, or organism (sometimes
the word pharmacon is used as a term to encompass these endogenous and
exogenous bioactive species). More specifically, it is the study of the
interactions that occur between a living organism and chemicals that
affect normal or abnormal biochemical function. If substances have
medicinal properties, they are considered pharmaceuticals.
Alchemy is change of one
substance into another, Transmutation
of metals aimed to purify,
mature, and perfect certain objects.
is a legendary alchemical substance
capable of turning base metals such as mercury into gold.
is a material engineered to have a property that is not found in nature.
They are made from assemblies of multiple elements fashioned from
composite materials such as metals or plastics.
Chemistry Tools and Equipment
Laboratory Equipment Names and Chemistry Lab Tools
Chemistry Set HistoryDo It
bioengineers develop a 20-cent, hand-powered centrifuge
ultralow-cost paper centrifuge, or paperfuge." With rotational speeds of
up to 125,000 revolutions per minute, the device separates blood plasma
from red cells in 1.5 minutes, no electricity required. A centrifuge is
critical for detecting diseases such as malaria, African sleeping
sickness, HIV and tuberculosis. This low-cost version will enable precise
diagnosis and treatment in the poor, off-the-grid regions where these
diseases are most prevalent.
is a piece of equipment that puts an object in rotation
around a fixed axis (spins it in a circle), applying a potentially strong
force perpendicular to the axis of spin (outward). The centrifuge works
using the sedimentation principle, where the centripetal acceleration
causes denser substances and particles to move outward in the radial
direction. At the same time, objects that are less dense are displaced
and move to the center. In a laboratory centrifuge that uses sample
tubes, the radial acceleration causes denser particles to settle to the
bottom of the tube, while low-density substances rise to the top. There
are 3 types of centrifuge designed for different applications. Industrial
scale centrifuges are commonly used in manufacturing and waste processing
to sediment suspended solids, or to separate immiscible liquids. An
example is the cream separator found in dairies. Very high speed
centrifuges and ultracentrifuges able to provide very high accelerations
can separate fine particles down to the nano-scale
different masses. Large centrifuges are used to simulate high gravity or
acceleration environments (for example, high-G training for test pilots).
Medium-sized centrifuges are used in washing machines and at some
swimming pools to wring water out of fabrics. Gas centrifuges are used
for isotope separation, such as to enrich nuclear fuel for fissile
American Chemical Society
American Chemical Society
Industrial & Engineering Chemistry Research
The American Oil
Royal Society of