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Biology

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Biology is a branch of science, dealing with the study of life. It is concerned with the characteristics, classification, and behaviors of organisms, how species come into existence, and the interactions they have with each other and with the environment. Biology encompasses a broad spectrum of academic fields that are often viewed as independent disciplines. However, together they address phenomena related to living organisms (biological phenomena) over a wide range of scales, from biochemistry to ecology.

Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle

At the organism level, biology has explained phenomena such as birth, growth, ageing, death and decay of living organisms, similarities between the offsprings and parents (heredity) and flowering of plants have puzzled humanity ever since antiquity. Other phenomena, such as lactation, metamorphosis, egg-hatching, healing, and tropism have been addressed. On a wider scale of time and space, biologists have studied domestication of animals and plants, the wide variety of living organisms (biodiversity), changes in living organisms through ages (evolution), extinction, speciation, social behaviour among animals, etc.

While botany encompasses the study of plants, zoology is the branch of science that is concerned about the study of animals and anthropology is the branch of biology to study human beings. However, at the molecular scale, life is studied in the disciplines of molecular biology, biochemistry, and molecular genetics. At the next level of the cell, it is studied in cell biology, and at multicellular scales, it is examined in physiology, anatomy, and histology. Developmental biology studies life at the level of an individual organism’s development or ontogeny. Moving up the scale towards more than one organism, genetics considers how heredity works between parent and offspring. Ethology considers group behavior of more than one individual. Population genetics looks at the level of an entire population, and systematics considers the multi-species scale of lineages. Interdependent populations and their habitats are examined in ecology and evolutionary biology. A speculative new field is astrobiology (or xenobiology), which examines the possibility of life beyond the Earth.

Principles of biology

Unlike physics, biology does not usually describe systems in terms of objects which obey immutable physical laws described by mathematics. Nevertheless, the biological sciences are characterized and unified by several major underlying principles and concepts: universality, evolution, diversity, continuity, genetics, homeostasis, and interactions.

Universality: Biochemistry, cells, and the genetic code

Schematic representation of DNA, the primary genetic material.

Main article: Life

The most salient example of biological universality is that all living things share a common carbon-based biochemistry and in particular pass on their characteristics via genetic material, which is based on nucleic acids such as DNA and which uses a common genetic code with only minor variations.

Another universal principle is that all organisms (that is, all forms of life on Earth except for viruses) are made of cells. Similarly, all organisms share common developmental processes. For example, in most metazoan organisms, the basic stages of early embryonic development share similar morphological characteristics and include similar genes.

Evolution: The central principle of biology

Main article: Evolution

The central organizing concept in biology is that all life has a common origin and has changed and developed through the process of evolution (see Common descent). This has led to the striking similarity of units and processes discussed in the previous section. Charles Darwin established evolution as a viable theory by articulating its driving force, natural selection (Alfred Russell Wallace is recognized as the co-discoverer of this concept). Genetic drift was embraced as an additional mechanism of evolutionary development in the modern synthesis of the theory.

The evolutionary history of a species— which describes the characteristics of the various species from which it descended— together with its genealogical relationship to every other species is called its phylogeny. Widely varied approaches to biology generate information about phylogeny. These include the comparisons of DNA sequences conducted within molecular biology or genomics, and comparisons of fossils or other records of ancient organisms in paleontology. Biologists organize and analyze evolutionary relationships through various methods, including phylogenetics, phenetics, and cladistics (The major events in the evolution of life, as biologists currently understand them, are summarized on this evolutionary timeline).

Diversity: The variety of living organisms

A phylogenetic tree of all living things, based on rRNA gene data, showing the separation of the three domains bacteria, archaea, and eukaryotes as described initially by Carl Woese. Trees constructed with other genes are generally similar, although they may place some early-branching groups very differently, presumably owing to rapid rRNA evolution. The exact relationships of the three domains are still being debated.

Despite its underlying unity, life exhibits an astonishingly wide diversity in morphology, behavior, and life histories. In order to grapple with this diversity, biologists attempt to classify all living things. Scientific classification seeks to reflect the evolutionary trees (phylogenetic trees) of the organism being classified. Classification is the province of the disciplines of systematics and taxonomy. Taxonomy places organisms in groups called taxa, while systematics seeks to define their relationships with each other. This clasification technique has evolved to reflect advances in cladistics and genetics, shifting the focus from physical similarities and shared characteristics to phylogenetics.

Traditionally, living things have been divided into five kingdoms:

Monera — Protista — Fungi — Plantae — Animalia

However, many scientists now consider this five-kingdom system to be outdated. Modern alternative classification systems generally begin with the three-domain system:

Archaea (originally Archaebacteria) — Bacteria (originally Eubacteria) — Eukaryota

These domains reflect whether the cells have nuclei or not, as well as differences in the cell exteriors.

Further, each kingdom is broken down continuously until each species is separately classified. The order is 1)Kingdom, 2)Phylum, 3)Class, 4)Order, 5)Family, 6)Genus, 7)Species. The scientific name of an organism is obtained from its Genus and Species. For example, humans would be listed as Homo sapien. Homo would be the Genus and Sapien is the species. Whenever writing the scientific name of an organism it is proper to capitalize the first letter in the genus and all of the species is lowercase; in addition the entire term would be put in italics. The term used for classification is called Taxonomy.

There is also a series of intracellular parasites that are progressively “less alive” in terms of metabolic activity:

Viruses — Viroids — Prions

Continuity: The common descent of life

Main article: Common descent

Up into the 19th century, it was commonly believed that life forms could appear spontaneously under certain conditions (see abiogenesis). This misconception was challenged by William Harvey’s diction that “all life [is] from [an] egg” (from the Latin “Omne vivum ex ovo”), a foundational concept of modern biology. It simply means that there is an unbroken continuity of life from its initial origin to the present time.

A group of organisms is said to share a common descent if they share a common ancestor. All organisms on the Earth have been and are descended from a common ancestor or an ancestral gene pool. This last universal common ancestor of all organisms is believed to have appeared about 3.5 billion years ago. Biologists generally regard the universality of the genetic code as definitive evidence in favor of the theory of universal common descent (UCD) for all bacteria, archaea, and eukaryotes (see: origin of life).

Homeostasis: Adapting to change

Main article: Homeostasis

Homeostasis is the ability of an open system to regulate its internal environment to maintain a stable condition by means of multiple dynamic equilibrium adjustments controlled by interrelated regulation mechanisms. All living organisms, whether unicellular or multicellular, exhibit homeostasis. Homeostasis manifests itself at the cellular level through the maintenance of a stable internal acidity (pH); at the organismic level, warm-blooded animals maintain a constant internal body temperature; and at the level of the ecosystem, as when atmospheric carbon dioxide levels rise and plants are theoretically able to grow healthier and remove more of the gas from the atmosphere. Tissues and organs can also maintain homeostasis.

Interactions: Groups and environments

Mutual symbiosis between clownfish of the genus Amphiprion that dwell among the tentacles of tropical sea anemones. The territorial fish protects the anemone from anemone-eating fish, and in turn the stinging tentacles of the anemone protects the clown fish from its predators

Every living thing interacts with other organisms and its environment. One reason that biological systems can be difficult to study is that so many different interactions with other organisms and the environment are possible, even on the smallest of scales. A microscopic bacterium responding to a local sugar gradient is responding to its environment as much as a lion is responding to its environment when it searches for food in the African savannah. For any given species, behaviors can be co-operative, aggressive, parasitic or symbiotic. Matters become more complex when two or more different species interact in an ecosystem. Studies of this type are the province of ecology.

Scope of biology

Main article: List of biology disciplines

Biology has become such a vast research enterprise that it is not generally regarded as a single discipline, but as a number of clustered sub-disciplines. This article considers four broad groupings. The first group consists of those disciplines that study the basic structures of living systems: cells, genes etc.; the second group considers the operation of these structures at the level of tissues, organs, and bodies; the third group considers organisms and their histories; the final constellation of disciplines focuses on their interactions. It is important to note, however, that these boundaries, groupings, and descriptions are a simplified characterization of biological research. In reality, the boundaries between disciplines are fluid, and most disciplines frequently borrow techniques from each other. For example, evolutionary biology leans heavily on techniques from molecular biology to determine DNA sequences, which assist in understanding the genetic variation of a population; and physiology borrows extensively from cell biology in describing the function of organ systems.

Structure of life

Schematic of typical animal cell depicting the various organelles and structures

Main articles: Molecular biology, Cell biology, Genetics, Developmental biology

Molecular biology is the study of biology at a molecular level. This field overlaps with other areas of biology, particularly with genetics and biochemistry. Molecular biology chiefly concerns itself with understanding the interactions between the various systems of a cell, including the interrelationship of DNA, RNA, and protein synthesis and learning how these interactions are regulated.

Cell biology studies the physiological properties of cells, as well as their behaviors, interactions, and environment. This is done both on a microscopic and molecular level. Cell biology researches both single-celled organisms like bacteria and specialized cells in multicellular organisms like humans.

Understanding cell composition and how they function is fundamental to all of the biological sciences. Appreciating the similarities and differences between cell types is particularly important in the fields of cell and molecular biology. These fundamental similarities and differences provide a unifying theme, allowing the principles learned from studying one cell type to be extrapolated and generalized to other cell types.

Genetics is the science of genes, heredity, and the variation of organisms. In modern research, genetics provides important tools in the investigation of the function of a particular gene, or the analysis of genetic interactions. Within organisms, genetic information generally is carried in chromosomes, where it is represented in the chemical structure of particular DNA molecules.

Genes encode the information necessary for synthesizing proteins, which in turn play a large role in influencing (though, in many instances, not completely determining) the final phenotype of the organism.

Developmental biology studies the process by which organisms grow and develop. Originating in embryology, modern developmental biology studies the genetic control of cell growth, differentiation, and “morphogenesis,” which is the process that gives rise to tissues, organs, and anatomy. Model organisms for developmental biology include the round worm Caenorhabditis elegans, the fruit fly Drosophila melanogaster, the zebrafish Brachydanio rerio, the mouse Mus musculus, and the weed Arabidopsis thaliana.

Physiology of organisms

Main articles: Physiology, Anatomy

Physiology studies the mechanical, physical, and biochemical processes of living organisms by attempting to understand how all of the structures function as a whole. The theme of “structure to function” is central to biology. Physiological studies have traditionally been divided into plant physiology and animal physiology, but the principles of physiology are universal, no matter what particular organism is being studied. For example, what is learned about the physiology of yeast cells can also apply to human cells. The field of animal physiology extends the tools and methods of human physiology to non-human species. Plant physiology also borrows techniques from both fields.

Anatomy is an important branch of physiology and considers how organ systems in animals, such as the nervous, immune, endocrine, respiratory, and circulatory systems, function and interact. The study of these systems is shared with medically oriented disciplines such as neurology and immunology.

Diversity and evolution of organisms

In population genetics the evolution of a population of organisms is sometimes depicted as if travelling on a fitness landscape. The arrows indicate the preferred flow of a population on the landscape, and the points A, B, and C are local optima. The red ball indicates a population that moves from a very low fitness value to the top of a peak

Main articles: Evolutionary biology, Biodiversity, Botany, Zoology

Evolutionary biology is concerned with the origin and descent of species, as well as their change over time, and includes scientists from many taxonomically-oriented disciplines. For example, it generally involves scientists who have special training in particular organisms such as mammalogy, ornithology, or herpetology, but use those organisms as systems to answer general questions about evolution. Evolutionary biology is mainly based on paleontology, which uses the fossil record to answer questions about the mode and tempo of evolution, as well as the developments in areas such as population genetics and evolutionary theory. In the 1990s, developmental biology re-entered evolutionary biology from its initial exclusion from the modern synthesis through the study of evolutionary developmental biology. Related fields which are often considered part of evolutionary biology are phylogenetics, systematics, and taxonomy.

The two major traditional taxonomically-oriented disciplines are botany and zoology. Botany is the scientific study of plants. Botany covers a wide range of scientific disciplines that study the growth, reproduction, metabolism, development, diseases, and evolution of plant life. Zoology involves the study of animals, including the study of their physiology within the fields of anatomy and embryology. The common genetic and developmental mechanisms of animals and plants is studied in molecular biology, molecular genetics, and developmental biology. The ecology of animals is covered under behavioral ecology and other fields.

Classification of life

The dominant classification system is called Linnaean taxonomy, which includes ranks and binomial nomenclature. How organisms are named is governed by international agreements such as the International Code of Botanical Nomenclature (ICBN), the International Code of Zoological Nomenclature (ICZN), and the International Code of Nomenclature of Bacteria (ICNB). A fourth Draft BioCode was published in 1997 in an attempt to standardize naming in these three areas, but it has yet to be formally adopted. The International Code of Virus Classification and Nomenclature (ICVCN) remains outside the BioCode.

Interactions of organisms

A food web, a generalization of the food chain, depicting the complex interrelationships among organisms in an ecosystem.

Main articles: Ecology, Ethology, Behavior, Biogeography

Ecology studies the distribution and abundance of living organisms, and the interactions between organisms and their environment. The environment of an organism includes both its habitat, which can be described as the sum of local abiotic factors such as climate and geology, as well as the other the organisms that share its habitat. Ecological systems are studied at several different levels, from individuals and populations to ecosystems and the biosphere. As can be surmised, ecology is a science that draws on several disciplines.

Ethology studies animal behavior (particularly of social animals such as primates and canids), and is sometimes considered a branch of zoology. Ethologists have been particularly concerned with the evolution of behavior and the understanding of behavior in terms of the theory of natural selection. In one sense, the first modern ethologist was Charles Darwin, whose book The expression of the emotions in animals and men influenced many ethologists.

Biogeography studies the spatial distribution of organisms on the Earth, focusing on topics like plate tectonics, climate change, dispersal and migration, and cladistics.

History of the word “biology”

Formed by combining the Greek βίος (bios), meaning ‘life’, and λόγος (logos), meaning ’study of’, the word “biology” in its modern sense seems to have been introduced independently by Gottfried Reinhold Treviranus (Biologie oder Philosophie der lebenden Natur, 1802) and by Jean-Baptiste Lamarck (Hydrogéologie, 1802). The word itself is sometimes said to have been coined in 1800 by Karl Friedrich Burdach, but it appears in the title of Volume 3 of Michael Christoph Hanov’s Philosophiae naturalis sive physicae dogmaticae: Geologia, biologia, phytologia generalis et dendrologia, published in 1766.

History

Main articles: History of biology, History of medicine, History of genetics

Major discoveries in biology include:

• Cell theory
• Germ theory of disease
• Genetics
• Evolution
• DNA

See also

Main articles: List of biology topics

External links

Wikibooks has more about this subject:

Biology

Wikibooks Wikiversity has more about this subject:

School of Biology

• Biology News Net: Daily updated biology news & community website.
• BioNews :Latest Biology News : Research News and Articles from Biological Science and related fields.
• BioCode: A proposal for organism naming.
• NCBI Open-Access Books
• PhyloCode, [1]
• The Tree of Life: A multi-authored, distributed Internet project containing information about phylogeny and biodiversity.
• BioOne Bioscience research journals.
• EverythingBio Protocols, graduate school information, hard to find definitions.

Journal Links

• PLos Biology A peer-reviewed, open-access journal published by the Public Library of Science
• Perspectives in Biology and Medicine
• Biology for school and university - Graphics

Further reading

• Lynn Margulis, Five Kingdoms: An Illustrated Guide to the Phyla of Life on Earth, 3rd ed., St. Martin’s Press, 1997, paperback, ISBN 0805072527 (many other editions)
• Neil Campbell, Biology (7th edition), Benjamin-Cummings Publishing Company, 2004, hardcover, ISBN 080537146X

Bulk property

In chemistry, materials science, and other scientific disciplines, a bulk property of a substance is one that is independent of the amount of that substance being measured.

For instance, the mass of a substance is not a bulk property, because it depends on the amount of that substance being measured; one cubic meter of lead weighs a million times as much as a cubic centimeter of lead. However, both have the same density; thus, density is a bulk property.

Other examples of bulk properties include refractive index, concentration, half-life, elastic modulus, and tensile strength.

The concept is similar to that of per capita measurements in economics.

Catenation

Catenation is the ability of some elements to form chains of identical atoms. Carbon is the premier element in this respect, but some other elements (for instance, sulfur, silicon, and germanium) possess the property to a lower degree.

Carbon can form covalent bonds with two other carbon atoms and thus can form chains and rings. Aliphatic and aromatic hydrocarbons are examples of catenation. The propensity for catenation is high in carbon because the bond energy of the carbon-carbon bond is high in comparision to the energy of bonds of carbon with other elements.

Other elements, including some Chalcogens such as Sulfur and Oxygen, can also form chain structures. In the case of oxygen, only two-atom chain can be formed.Peroxide is an example. However, for sulfur, 8-atom (or even more than cation is fairly common.

This chemistry article is a stub. You can help Wikipedia by expanding it.

Caustic (substance)

A caustic substance, in chemistry, is one that causes corrosion, the deterioration of a material. Caustic literally means burning. A caustic substance can be acidic or basic, and concentrated solutions of acids and bases are common corrosive substances. Sodium Hydroxide, also known as caustic soda, is one example. Caustic substances are harmful to living tissue and structures, but they have beneficial uses. For example, drain cleaners often use caustic substances such as NaOH to clear clogged drains.

Chartered Chemist

Chartered Chemist (CChem) is a chartered status awarded by the Royal Society of Chemistry (RSC) in the United Kingdom and by the Royal Australian Chemical Institute (RACI) in Australia.

In the United Kingdom CChem candidates must meeting the following requirements:

• Be a Member or a Fellow of the RSC;
• Hold a degree accredited by the RSC (or equivalent);
• Show that the chemical knowledge and skills acquired from their education and training are essential for fulfilling the needs of their job;
• Demonstrate development of twelve Professional Attributes.

In Australia the requirements are broadly the same as above.

Reference

• RSC CChem information

This chemistry article is a stub. You can help Wikipedia by expanding it.

Chemical accidents

Chemical accidents are unanticipated releases, explosions, fires and other harmful incidents involving toxic and hazardous materials. While chemical accidents may occur whenever toxic materials are stored, transported or used, the most severe accidents tend to involve major chemical manufacturing and storage facilities. Significant events include the Bhopal Disaster of 1984, which released a highly toxic gas at a Union Carbide pesticides facility and killed more than 2,000 people.

Efforts to prevent accidents range from improved safety systems to fundamental changes in chemical use and manufacture, referred to as primary prevention or inherent safety.

In the U.S., concern about chemical accidents after the Bhopal disaster led to the passage of the 1986 Emergency Planning and Community Right-to-Know Act. The EPCRA requires local emergency planning efforts throughout the country, including emergency notifications. The law also requires companies to make publicly available information about their storage of toxic chemicals. Based on such information, citizens can identify the vulnerable zones in which severe toxic releases could cause harm or death.

In 1990, the U.S. Chemical Safety and Hazard Investigation Board was established by Congress, though the CSB did not become operational until 1998. The Board’s mission is to determine the root causes of chemical accidents and issue safety recommendations to prevent future accidents.

External links

• Case Studies in Process Plant Accidents
• http://online.safetysmart.com/chemical_safety.php
• U.S. Chemical Safety and Hazard Investigation Board [1]
• U.S. EPA, Chemical Emergency Preparedness and Prevention Office [2]
• Chemical and Other Safety Information - Oxford University
• Arc Flash Resource Center
• Safety in the use of Chemicals at work - International Labour Organization (ILO) - (PDF-file)
• Using Morphological Analysis to Evaluate Preparedness for Accidents Involving Hazardous Materials From the Swedish Morphological Society

Chemical change

A chemical change is a process in which reactants are changed into one or more different products. A chemical change occurs whenever new compounds are formed or existing compounds decomposed. During this reaction, chemical bonds between atoms are broken and new chemical bonds formed. This results in a rearrangement of the chemical bonds.

There are several different types of chemical change. These include synthesis, decomposition, single displacement, double displacement, neutralization, precipitation and redox.

Indicators of a chemical change include a colour change, the formation of a precipitate, the formation of gas, production of heat or light, the appearance of a new substance, a use-up of a starting substance or a change in temperature or energy. When new substances are formed, a chemical change has occurred, and a chemical reaction has taken place.

External links

• Online introduction into chemical change

Chemical equation

A chemical equation is a symbolic representation of a chemical reaction. It is a formula used to display different stages for chemical reactions, where chemical substances are changed into other substances. The elements and/or compounds to the left of the arrow in a chemical equation represent the reactants, the arrow represents the transition stage, and the species to the right of the arrow represent the products. The four basic chemical equations are:

A → B

A → B + C

A + B → C

A + B → B + C

For example, the combustion of methane in oxygen is depicted as:

CH₄ + 2 O₂ → CO₂ + 2 H₂O,

and the reversible reaction of the Haber process is shown as

N_2(g) + 3H_2(g) ⇌ 2NH_3(g) + ΔH.

A chemical equation should represent the stoichiometry observed in the chemical reaction. When the net amount of atoms on both sides of the equation is identical the equation is said to be a balanced equation.

Reading chemical equations

When reading a chemical equation there are some points to consider.

• Each side of an equation represents a mixture of chemicals. The mixture is written as a set of molecular formulas, separated by + symbols.
• Each formula is preceded by an optional scalar number (if no scalar number is written, it is implied that the number is 1). The scalar numbers indicate the relative quantity of molecules in the reaction. For instance, the string 2H₂O + 3CH₄ represents a mixture containing 2 molecules of H₂O for every 3 molecules of CH₄.
• The two sides of the equation are separated by an arrow. If the reaction is non-reversible, a right-arrow (→) is used, indicating that the left side represents the mixture of chemicals before the reaction, and the right side indicates the mixture after the reaction. For a reversible reaction, a two-way arrow is used. For example the equation 4Na + O₂ → 2Na₂O represents a non-reversible reaction. In this reaction, sodium (Na) and oxygen (O₂) are converted to a single molecule, Na₂O (containing 2 sodium atoms and 1 oxygen atom). We can also see that for every 4 sodium atoms at the beginning of the reaction, a single O₂ molecule will participate, and 2 Na₂O molecules will result.
• A chemical equation does not imply that all reactants are consumed in a chemical process. For instance a limiting reagent determines how far a reaction can go.
• In an ionic equation balancing of charge also takes place. In a full equation all reacts are written as molecules.

Balancing chemical equations

In a chemical reaction, the quantity of each element does not change. Thus, each side of the equation must represent the same quantity of any particular element. Also in case of net ionic reactions the same charge must be present on both sides of the equation. Then, and only then, the equation is balanced. Given an unbalanced equation, one may balance it by changing the scalar number for each molecular formula.

Simple chemical equations can be balanced by inspection, that is, by trial and error. Generally, it is best to balance the most complicated molecule first. Hydrogen and oxygen are usually balanced last.

Ex #1. Na + O₂ → Na₂O

In order for this equation to be balanced, there must be an equal amount of Na on the left hand side as on the right hand side. As it stands now, there is 1 Na on the left but 2 Na’s on the right. This problem is solved by putting a 2 in front of the Na on the left hand side:

2Na + O₂ → Na₂O

In this equation there are 2 Na atoms on the left and 2 Na atoms on the right. In the next step the oxygen atoms are balanced as well. On the left hand side there are 2 O atoms and the right hand side only has one. This is still an unbalanced equation. To fix this a 2 is added in front of the Na₂O on the right hand side. Now the equation reads:

2Na + O₂ → 2Na₂O

Notice that the 2 on the right hand side is “distributed” to both the Na₂ and the O. Currently the left hand side of the equation has 2 Na atoms and 2 O atoms. The right hand side has 4 Na’s total and 2 O’s. Again, this is a problem, there must be an equal amount of each chemical on both sides. To fix this 2 more Na’s are added on the left side. The equation will now look like this:

4Na + O₂ → 2Na₂O

This equation is a balanced equation because there is an equal amount of element’s on the left and right hand sides of the equation.

Ex #2. P₄ + O₂ → P₄O₁₀

This equation is not balanced because there is an unequal amount of O’s on both sides of the equation. The left hand side has 4 P’s and the right hand side has 4 P’s. So the P atoms are balanced. The left hand side has 2 O’s and the right hand side has 10 O’s. To fix this unbalanced equation a 5 in front of the O₂ on the left hand side is added to make 10 O’s on both sides resulting in

P₄ + 5O₂ → P₄O₁₀

The equation is now balanced because there is an equal amount of substances on the left and the right hand side of the equation.

Ex #3. C₂H₅OH + O₂ → CO₂ + H₂O

This equation is more complex than the previous examples and requires more steps. The most complicated molecule here is C₂H₅OH, so balancing begins by placing the coefficient 2 before the CO₂ to balance the carbon atoms.

C₂H₅OH + O₂ → 2CO₂ + H₂O

Since C₂H₅OH contains 6 hydrogen atoms, the hydrogen atoms can be balanced by placing 3 before the H₂O:

C₂H₅OH + O₂ → 2CO₂ + 3H₂O

Finally the oxygen atoms are balanced. Since there are 7 oxygen atoms on the right and only 3 on the left, a 3 is placed before O₂, to produce the balanced equation:

C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O

Linear system balancing

In reactions involving many compounds, balancing may get harder, in that situation one can try balancing using a linear system:

1. Assign variables to each coefficient:

• a K₄Fe(CN)₆ + b H₂SO₄ + c H₂O → d K₂SO₄ + e FeSO₄ + f (NH₄)₂SO₄ + g CO

2. We must have the same quantities of each atom in each side of the equation. So, for each element, count its atoms and equal both sides:

• K: 4a = 2d
• Fe: 1a = 1e
• C: 6a = g
• N: 6a = 2f
• H: 2b+2c = 8f
• S: b = d+e+f
• O: 4b+c = 4d+4e+4f+g

3. Solving the system(usually direct substitution is the best way)

• d=2a
• e=a
• g=6a
• f=3a
• b=6a
• c=6a

which means that we have all coefficients depending on a parameter a, just choose a=1(a number that will make all of them small whole numbers) and you’ll have:

• a=1 b=6 c=6 d=2 e=1 f=3 g=6

4. And the balanced equation at last:

• K₄Fe(CN)₆ + 6 H₂SO₄ + 6 H₂O → 2 K₂SO₄ + FeSO₄ + 3 (NH₄)₂SO₄ + 6 CO

To speed up the process, one can combine both methods to get a more practical algorithm:

1. Identify elements which occur in one compound in each member(this is very usual)

2. Start with the one among those which has a big index(this will help to keep working with integers), and assign a variable, let’s say a.

• a K₄Fe(CN)₆ + H₂SO₄ + H₂O → K₂SO₄ + FeSO₄ + (NH₄)₂SO₄ + CO

3. Well, K₂SO₄ has to be 2a(because of K), and also, FeSO₄ has to be 1a(because of Fe), CO has to be 6a(because of C) and (NH₄)₂SO₄ has to be 3a(because of N). Well, this takes out the first four equations of the system! We already now that, whatever the coefficients are, those proportions must hold:

• a K₄Fe(CN)₆ + H₂SO₄ + H₂O → 2a K₂SO₄ + a FeSO₄ + 3a (NH₄)₂SO₄ + 6a CO

4. We can continue by writing the equations now(and having simpler problem to solve) or, in this particular case(although not so particular) we could continue by noticing that adding the Sulfurs we get 6a for H₂SO₄ and finally by adding the hydrogens(or the oxygens) we get the lasting 6a for H₂SO₄.

5. Again, having a convenient value for a(in this case 1 will do, but if a gets fractionary values in the other coefficients you will like to cancel the denominators) we get the result:

• K₄Fe(CN)₆ + 6 H₂SO₄ + 6 H₂O → 2 K₂SO₄ + FeSO₄ + 3 (NH₄)₂SO₄ + 6 CO

External links

• Classic Chembalancer - Play Chembalancer, a free online game at FunBasedLearning.com, to learn how to balance equations by inspection
• Online calculator, determines of the coefficients of a chemical equation
• Chemical equation balancing program - works off-line, calculates stoichiometry and limiting reagents, balances charge.

Chemical industry

Chemical tanks in Lillebonne, France

The chemical industry refers to industry involved in the production of chemicals with high economic impact. These include petrochemicals, agrochemicals, pharmaceuticals, polymers, paints, and oleochemicals. Chemical processes are used, including chemical reactions to form new substances, separations based on properties such as solubility or ionic charge, and distillations, in addition to transformations by heating and other methods.

Chemical industries involve the processing of, or change in, raw materials obtained by mining, and agriculture among other supply sources, into materials and substances that are useful on their own, or in other industries. The food processing industries are generally not included in the term “chemical industry”.

Companies

The biggest companies in chemical industry on Earth are listed with business volume in billions of Euros.

• Badische Anilin- und Soda-Fabrik (BASF)(D) 28 (formerly IG-Farben)
• Dow Chemical (USA) 27
• DuPont (USA) 24
• Bayer (D) 20 (formerly IG-Farben)
• ExxonMobil Chemicals (USA) 20 (formerly Standard Oil)
• Atofina (F) 20
• BP Chemicals (GB) 13
• Mitsubishi Chemicals (J) 12
• Deutsche Gold- und Silber-Scheide-Anstalt (DEGUSSA)(D) 11(formerly IG-Farben)
• Shell Chemicals (NL/GB) 11

Chemical law

Chemical laws are those laws of nature relevant to chemistry. The most fundamental concept in chemistry is the law of conservation of mass, which states that there is no detectable change in the quantity of matter during an ordinary chemical reaction. Modern physics shows that it is actually energy that is conserved, and that energy and mass are related; a concept which becomes important in nuclear chemistry. Conservation of energy leads to the important concepts of equilibrium, thermodynamics, and kinetics.

Further laws of chemistry elaborate on the law of conservation of mass. Joseph Proust’s law of definite composition says that pure chemicals are composed of elements in a definite formulation; we now know that the structural arrangement of these elements is also important.

Dalton’s law of multiple proportions says that these chemicals will present themselves in proportions that are small whole numbers (i.e. 1:2 O:H in water); although in many systems (notably biomacromolecules and minerals) the ratios tend to require large numbers, and are frequently represented as a fraction. Such compounds are known as non-stoichiometric compounds

More modern laws of chemistry define the relationship between energy and transformations.

• In equilibrium, molecules exist in mixture defined by the transformations possible on the timescale of the equilibrium, and are in a ratio defined by the intrinsic energy of the molecules—the lower the intrinsic energy, the more abundant the molecule.
• Transforming one structure to another requires the input of energy to cross an energy barrier; this can come from the intrinsic energy of the molecules themselves, or from an external source which will generally accelerate transformations. The higher the energy barrier, the slower the transformation occurs.
• There is a hypothetical intermediate, or transition structure, that corresponds to the structure at the top of the energy barrier. The Hammond-Leffler Postulate states that this structure looks most similar to the product or starting material which has intrinsic energy closest to that of the energy barrier. Stabilizing this hypothetical intermediate through chemical interaction is one way to achieve catalysis.
• All chemical processes are reversible (law of microscopic reversibility) although some processes have such an energy bias, they are essentially irreversible.