GÖTZINGER

We build special machines for the production of louvre doors, consisting of an automatic louvre cutter, a heading device and a louvre frame clamp. Our range also includes finger-jointing lines consisting of a finger jointing clamp, a glue applicator and a finger jointing cutter formerly built by FESTO/HOLZ-HER and the K 15 hole and harware boring machine. The same applies, for example, to the rod profiler, the universal profiler, the wall-mounting and pedestal-type chain mortiser, and supplies of spare parts for the type ZA tenon and mortise cutting machine. We have designed and built a door support to supplement the wall-mounting and pedestal-type chain mortiser. Other successful products include the olive boring machine (for olive-shaped handles) and a corner-bearing boring machine as a low-price accessory. We also build special machines to customer wishes.

Product range
image 1, source: GÖTZINGER

Machine Tools Germany - Deutschland Machine Tools Supplier

The company Aachener Maschinenbau (AMBA) was founded in Aachen in 1908. About 50 years ago AMBA started manufacturing machines for production of spokes and nipples for bicycles and motorbikes. Based on these products the first AMBA boltmaker was developed.

Today AMBA boltmakers and other cold forming machines are found in the fastener industry worldwide. Main advantage of AMBA boltmakers is their modular set-up which combines heading and threading in one machine including the possibility of two different threads on the blank. A full-size AMBA BM 12 for example includes cutting, heading, extruding, pointing and threading for screws and bolt up to ½" in diameter and 60" in length. A high-speed AMBA 68 for screws size ¼" x 10" is capable to produce up to 230 ppm.

The first flat die thread roller worldwide to produce full threaded screws up to 600 mm (24") in length was developed in 2005. This machine can be equipped with dies up to 12" in length. Currently AMBA is projecting a new generation of flat die thread roller with dies up to 24" in length.

Nonwovens / Technical Textiles

Nonwovens For Medical Applications
Innovations in the growing nonwoven medical textiles sector include new products aimed at infection prevention.
Janet Bealer Rodie, Managing Editor
N onwoven textiles play a significant role in the medical sector. The product range includes surgical gowns, masks and other wearable products; surgical drapes, pads; dressings; filtration materials; and implantable textiles such as tissue scaffolds for rebuilding internal organs, among other products.

By far, most nonwoven products used outside the body are disposable, single-use articles that have the advantage of not requiring sterilization or cleaning for reuse. However, there are some that can be reused to provide the required function over a limited period of time.

In North America, disposable nonwoven medical apparel products alone represent a market totaling nearly $1.46 billion, according to the Association of the Nonwoven Fabrics Industry (INDA), Cary, N.C.; and the market is growing by approximately 1 to 2 percent annually. Globally, the medical nonwoven disposables market is forecast to grow to $12 billion annually by 2010, according to market research firm Global Industry Analysts Inc., San Jose, Calif.

Products used inside the body may provide a basis for cells to grow and regenerate tissue — for example, a ligament that has been destroyed or damaged that can be regenerated using a bioabsorbable material that eventually becomes indistinguishable from the ligament itself.

Manufacturing processes used to make these medical nonwovens include needlepunch; hydroentangling; spunbond, meltblown and a combination of the two; and thermal bonding. Bicomponent splittable or fibrillated fibers, nanotechnology and fiber modification also play important roles in some recent developments, a number of them involving filtration and barrier technologies.

“Nanofibers are becoming very popular for medical textiles used to filter viruses and bacteria,” said Jeff Haggard, vice president of technology at West Melbourne, Fla.-based Hills Inc., a developer of man-made fiber technology and machinery. Hills has been a pioneer in the development of bicomponent fibers as well as meltblown and spunbond technologies and their applications, and it offers meltblown technology that can produce fibers in the range between 25 and 400 nanometers (nm), with an average size of 250 nm.

A Collaborative Development
Collaborations between research institutes and private industry have yielded numerous important developments in the nonwoven medical textile field. As one example, Pathogen Removal and Diagnostic Technologies Inc. (PRDT), a joint venture between ProMetic BioSciences Ltd., England, and the American Red Cross, Washington, has developed a filter to remove prion protein from red blood cell concentrate. Prions are responsible for degenerative brain diseases such as mad cow disease and other such diseases, including its human cousin and the target of this filter, variant Creutzfeld-Jakob disease. The filter, marketed in the United Kingdom by France-based MacoPharma S.A. under the brand name P-CAPT™, comprises a target-specific affinity resin sandwiched between nonwoven membranes using a calendering process. The membrane development was carried out through a collaboration with the Nonwovens Cooperative Research Center (NCRC) at North Carolina State University (NCSU). The effort brought together prion experts at the University of Maryland, and chemical engineers involved in bioseparations and NCRC nonwovens staff and engineers at NCSU.

The P-CAPT™ filter for removing prion protein from
red blood cell concentrate comprises a target-specific
affinity resin sandwiched between nonwoven membranes.
Photo and schematic courtesy of MacoPharma S.A.

Disease Prevention: Multiple-Use Protection
Current warnings of a swine flu (H1N1) pandemic must be providing a boon to nonwoven face mask and respirator sales, as people around the world have been shown wearing the masks in an effort to avoid inhaling the virus or spreading possible infection to others. The US Department of Health and Human Services has established a website, www.flu.gov, to provide information about H1N1, avian flu (H5N1) and pandemic flu in general. The website includes a page with information and guidance provided by the Centers for Disease Control and Prevention and the Occupational Safety and Health Administration about the use of masks and respirators to protect against infection. Numerous other websites offered by health organizations and governments around the world also provide relevant information.

Mask manufacturers reportedly are escalating their operations to meet the increased demand. “ We’ve gotten some big orders in several countries and are ramping up production,” said John Dolan, CEO, Carey International Ltd., a Westerly, R.I.-based worldwide distributor of a new, multiple-use respirator mask made with a needlepunched, four-ply fabric comprising two outer layers featuring Agion® silver/copper zeolite compounds permanently embedded into the fiber and two inner filtration layers to prevent microbial or other particle penetration. The outer layers have been shown to kill Streptococcus pyogenes, methicillin-resistant Staphylococcus aureus and other bacteria; and inactivate H1N1, H5N1, the common cold and other viruses. The filtration layers comply with National Institute of Occupational Safety and Health N95 and N99 standards.

The N99 mask — certified according to European Respiratory Protection Standard EN149:2001 FFP3 level to have 99-percent-or-greater particle filtration effcacy, and also approved by Canadian regulatory agencies — is currently available outside the United States. It has been shown in trials to be effective for at least 28 days, compared with eight to 12 hours effective use for standard single-use masks; and the cost per day of use of the mask is about one-tenth of the cost of a single-use mask.

Bill Hurst, director of business development at Wakefield, Mass.-based Agion, said the silver and copper work synergistically to provide faster antimicrobial action than silver alone. “ The ionic exchange between the copper and the sulfur that makes up the bacterium cell membrane helps compromise that membrane,” he said.

Conclusion
Products such as the P-CAPT blood filter and the N99 respirator mask are but two innovations being offered in the growing nonwoven medical textile market. New fiber and processing technologies as well as collaborative, multidisciplinary efforts will contribute to ongoing product development and further market growth.

Undergraduate Frequently Asked Questions

About the Field
What is Chemical Engineering?
Chemical Engineering combines math, physics, chemistry, biology, and engineering to solve a wide range of industrial problems in a safe and economical fashion.

How long does it take to become a Chemical Engineer?
The B.S. program in Chemical Engineering takes five years to complete. During these five years, students receive 36 months (12 terms) of resident instruction and three 6 month periods of practical engineering experience (Co-op) dispersed throughout the sophomore, pre-junior and junior years. By graduation, B.S. students have obtained a degree as well as practical work experience.

What career options do Chemical Engineers have?
Chemical engineers have career opportunities in chemical process industries (CPI), biotechnology, advanced materials, design and construction, electronics, environmental, safety, and health industries, the food and beverages industries, and many other industries.

Chemical Engineering

Students in Chemical Engineering graduate programs experience high-quality, challenging, and exciting interdisciplinary research in a dynamic and cohesive environment.
Graduate students have access to leading facilities within the department and the university, as well as to research groups with strong links to international researchers and industry (e.g. DuPont, Xerox, SAS, BP Chemicals France, Praxair). Finally, the program has a dynamic group of award-winning researchers that are strongly committed to research, graduate supervision and teaching at a nationally and internationally recognized research university

Adhesive Systems, Inc

If you are looking for adhesives, we have just about any kind that will satisfy your packaging and bottling needs.

Product Line:

Barrier Coatings
Hot Melt Adhesives
Low Application Temperature Adhesives
Radiation Curable Adhesives
Specialty Adhesives
Water-Base Adhesives
Pre-Applied Adhesives

Recycled Polymeric Materials

The commitment to creativity and belief in new technological possibilities by Diversified Chemical Technologies, Inc. has given life to Recycled Polymeric Materials (RPM).

RPM produces polyurethane components that contain 25% recycled rubber mesh from used tires. Via a patent-pending ambient temperature reaction injection molding process, this system combines the newest in Polyurethane chemistry with post-consumer waste material, producing components of virtually any geometry which can be used as direct replacements for vulcanized EPDM parts.
Our products can currently be found on over 17,000,000 Ford, GM, Honda, Nissan, DaimlerChrysler and BMW vehicles around the world, sealing areas most critical to OEMs.
Environmental Benefits
How often do you have the opportunity to protect the environment, improve your product, and improve your financials? Recycled Polymeric Materials products allow our automotive customers to achieve all of these goals.

Our commitment to both the environment and technological improvements, have led to the development of Foamed Rubber Parts made out of 30% recycled tire rubber. This line of products have proven to be lighter in weight, require less energy to manufacture, show an increase in durability, and assist in the elimination of 60,000 used tires every year.
Research & Development
The unique nature of RPM technology is that the scope is not confined to the automotive industry. On-going and future projects include rubberized concrete for reduced construction costs and increased durability. In addition, RPM is pursuing the use of ASR (automotive shredder residue) as a quality replacement for wood in multiple areas, which may also reduce construction costs. Future applications are being contemplated regarding the expansion of this technology, and RPM will be there.

CHEMICAL PROCESS EQUIPMENT

Anhydro is a leading global supplier of liquid concentration and powder processing solutions, as well as dewatering plants and equipment for the international dairy, food, beverage and alcohol, ethanol, starch, pharmaceutical and chemical industries.
Anhydro designs, manufactures, installs and services a wide range of advanced evaporation, drying and dewatering equipment for customers in major industries around the world.
CHEMICAL PROCESS EQUIPMENT
Common to the process industry is the challenge of globalization, continuous innovation, a constant demand for higher performance with lower costs, and the need for leading-edge technology supported by a global service organization.
Anhydro is a leading global supplier to the above mentioned industries offering technologically superior solutions and the flexibility and cost-effectiveness including:

1 Evaporators
2 Dryers
3 Fluid bed technology
4 Dewatering equipment

WORLDWIDE RESEARCH AND DEVELOPMENT, TECHNICAL CENTERS AND PRODUCTION SITES

With worldwide research and development, technical centers and production sites, Evonik Degussa ensures fast and efficient communication with its industry partners around the world.
Please also see Pharmaceutical Technology - Evonik Degussa - Homogeneous and Heterogeneous Catalysts, Biocatalysts and Screening Services

LIFE SCIENCES AND FINE CHEMICAL INDUSTRIES

For the life sciences and fine chemical industries, Evonik Degussa offers a broad range of precious metal powder and activated base metal catalysts and services throughout the metal loop. The life sciences and fine chemicals industries use catalytic reactions in a wide variety of applications, typically conducted in batch processes. These industries have an extensive range of catalytic needs from the optimum catalyst and reaction conditions in the process, to health and safety, strict confidentiality, right through to final product recycle or disposal.
POLYMERS
Polyolefins such as polyethylene (PE) and polypropylene (PP) make possible many of the items we use in our daily lives. These materials are widely used in the automotive industry, for instance in the production of bumpers, as well as in the manufacture of plastic shopping bags. As one of the world leaders in catalysis, we utilize all of our know-how for research and development of new materials. Our product line includes: magnesium ethoxide (a highly active support material for Ziegler-Natta catalysts), silane donors (used as additives for increasing the isotacticity in PP catalysts), and AEROCAT (a new silica support material for metallocenes and for Ziegler-Natta or phillips catalysts).

CONTINUOUS PROCESS CATALYSTS

Evonik Degussa provides Continuous Process Catalysts (CPC) for the industrial chemicals and intermediates industry. With worldwide customers and partners we have an excellent position in market segments such as solvents, plasticizers, monomers, intermediates and fine gas purification. Evonik Degussa's product portfolio for industrial chemicals and intermediates is comprised of the following products:
Aerocat®: a new silica support material for fluid bed applications.
Aerolyst®: unique silica and titania catalyst supports based on fumed oxides for fixed bed applications.
Noblyst®: supported precious metal catalysts for fixed bed hydrogenerations and oxidations.
Octolyst®: supported and bulk nickel, cobalt and copper catalysts for fixed bed hydrogenations and dehydrogenations.

Degussa

Evonik Degussa's solution partner approach and its continuous dialogue and collaboration with customers, speeds up and successfully completes the commercialisation process of custom-made catalysts, transforming lab recipes into commercial products. Evonik Degussa provides world-class quality products and services, many years of experience in catalysis and key proprietary technologies, as well as flexible and dedicated cross-functional project management teams comprising of research and development, production, sales and marketing. Evonik Degussa promotes and participates largely in global development.

Anhydro - Drying, Evaporation and Dewatering Solutions

Anhydro offers a complete spectrum of evaporation and drying equipment for the dairy, chemical, starch and ethanol industries spanning a wide range of technologies and capacities.

Fertilizers

Fertilizers By Engro Chemical Pakistan Limited

Nitrogenous Fertilizers ENGRO UREA is a trusted high grade fertilizer containing 46% Nitrogen (N), with moderate hydroscopicity. It has a pH value of 6.8 (organic molecule) and is suitable for all crops on all soils. Engro Urea is an excellent source of Nitrogen for the vast majority of cultivated soils of Pakistan. Phosphatic Fertilizers Engro DAP: contains 46% P2O5 and 18% N. More than 90% of Phosphate (P) is water soluble. It has a pH value of 7.33 and is a good source of P fertilizer for all crops. It is an equally good source on problem soils (saline sodic) with coarse texture. On an overall basis it suits to about 90% soils of the country. Engro Zorawar: is one of the highest grade phosphatic fertilizers. It is acidic in reaction (pH >= 3.5) and contains 52% P2O5 of which more than 90% is water soluble, while the rest is citrate soluble. In addition to P, it contains 12% N, 2% sulphur and 1% calcium. It is a beneficial fertilizer for all crops on all soils of Pakistan and produces excellent results on alkaline soils, due to its acidic The acidic pH of Engro Zorawar also tends to slow down the rapid conversion of soluble P to water insoluble compounds, keeping it plant available for a longer period of time. Engro Phosphate: is brown colored mono ammonium phosphate with 11% nitrogen and 52% phosphorus. It is being marketed as relatively cheaper alternate of DAP. Blended Fertilizers Engro Zarkhez: is homogenously granulated fertilizer which maximizes crop yield by providing balanced nutrition for a wide variety of crops through the uniform availability of Nitrogen, Phosphorous and Potassium. Engro Zarkhez grades are specially produced to suit the requirements of individual crops and soils, and provide convenience to the farmer through ready availability of precise quantities of primary nutrients. Engro Zarkhez fertilizers have low moisture content, high crush strength; 2mm-4mm granule size and free flowing nature - attributes which ensure excellent handling and application characteristics. Green 08:23:18 Potato, Maize, Sugarcane, Wheat, Cotton, Rice and Vegetables Blue 17:17:17 Citrus, Mango, Banana and Other Fruits Tobacco 12:15:20 Tobacco Engro NP: it provides 22% nitrogen, and 20% phosphorus. ECPL entered into NP business in 2005 to cater the need of its customers for this established category. Primary focus area for ENP marketing is South Zone (Sind). Micro Nutrients Zingro: Zinc Sulphate, a highly effective and potent fertilizer which primarily targets Zinc deficiency in crops like Rice, Potato, Maize, Sugar cane, Wheat, Cotton, vegetables and fruits. Zingro increases crop yield and enhances crop appearance.

Argus Chemicals

Argus Chemicals srl is a Rare & Fine Chemicals company in Vernio (North of Florence), Italy . The company was started in 1985 by Dr. Enrico Ammannati

to produce chemicals for the chemical and pharmaceutical industry. On a lab-scale basis, the company began to produce rare and otherwise unobtainable compounds, not generally found in commercial catalogues. Through the years the company expanded its capabilities up to Pilot-plant-scale to be able to satisfy the demand for kilo-batches of products involving air-sensitive reagents. Initially Argus was devoted to the production of phosphine based ligands for metal catalysts. Now it also offers a broad service of R&D under secrecy agreement for pharmaceutical firms.

The expert and enthusiastic team of chemists at Argus, is able to satisfy the needs of the customers in the field for complex multistep-syntheses, optimisation procedures, and scale-up syntheses.

The R&D and Production departments are fully integrated. "Ab initio" synthesis and scale-up (grams to kilos) constitute one of the major outsourcing proposals from our customers.

Chemical substance

A chemical substance is a material with a specific chemical composition. It is a concept that became firmly established in the late eighteenth century after work by the chemist Joseph Proust on the composition of some pure chemical compounds such as basic copper carbonate.^[1] He deduced that, "All samples of a compound have the same composition; that is, all samples have the same proportions, by mass, of the elements present in the compound." This is now known as the law of constant composition.^[2] Later with the advancement of methods for chemical synthesis particularly in the realm of organic chemistry; the discovery of many more chemical elements and new techniques in the realm of analytical chemistry used for isolation and purification of elements and compounds from chemicals that led to the establishment of modern chemistry, the concept was defined as is found in most chemistry textbooks. However, there are some controversies regarding this definition mainly because the large number of chemical substances reported in chemistry literature need to be indexed.

A common example of a chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory. A pure chemical substance cannot be separated into other substances by a process that does not involve any chemical reaction and is rarely found in nature. Some typical chemical substances can be diamond, gold, salt (sodium chloride) and sugar (sucrose). Generally, chemical substances exist as a solid, liquid, or gas, and may change between these phases of matter with changes in temperature or pressure.

Forms of energy, such as light and heat, are not considered to be matter, and thus they are not "substances" in the scientific regard.

Chemical equilibrium

In a chemical process, chemical equilibrium is the state in which the chemical activities or concentrations of the reactants and products have no net change over time. Usually, this would be the state that results when the forward chemical process proceeds at the same rate as their reverse reaction. The reaction rates of the forward and reverse reactions are generally not zero but, being equal, there are no net changes in any of the reactant or product concentrations. This process is called dynamic equilibrium. ^[1][2]

Introduction

In a chemical reaction, when reactants are mixed together in a reaction vessel (and heated if needed), the whole of reactants do not get converted into the products. After some time (which may be shorter than millionths of a second or longer than the age of the universe), the opposing reactions will have equal reaction rates, creating a dynamic equilibrium in which the ratio between reactants and products will appear fixed. This is called chemical equilibrium.

The concept of chemical equilibrium was developed after Berthollet (1803) found that some chemical reactions are reversible. For any reaction such as

to be at equilibrium the rates of the forward and backward (reverse) reactions have to be equal. In this chemical equation with arrows pointing both ways to indicate equilibrium, A and B are reactant chemical species, S and T are product species, and α, β, σ, and τ are the stoichiometric coefficients of the respective reactants and products. The equilibrium position of a reaction is said to lie far to the right if, at equilibrium, nearly all the reactants are used up and far to the left if hardly any product is formed from the reactants.

Guldberg and Waage (1865), building on Berthollet’s ideas, proposed the law of mass action:

where A, B, S and T are active masses and k₊ and k₋ are rate constants. Since forward and backward rates are equal:

and the ratio of the rate constants is also a constant, now known as an equilibrium constant.

By convention the products form the numerator. However, the law of mass action is valid only for concerted one-step reactions that proceed through a single transition state and is not valid in general because rate equations do not, in general, follow the stoichiometry of the reaction as Guldberg and Waage had proposed (see, for example, nucleophilic aliphatic substitution by S_N1 or reaction of hydrogen and bromine to form hydrogen bromide). Equality of forward and backward reaction rates, however, is a necessary condition for chemical equilibrium, though it is not sufficient to explain why equilibrium occurs.

Despite the failure of this derivation, the equilibrium constant for a reaction is indeed a constant, independent of the activities of the various species involved, though it does depend on temperature as observed by the van 't Hoff equation. Adding a catalyst will affect both the forward reaction and the reverse reaction in the same way and will not have an effect on the equilibrium constant. The catalyst will speed up both reactions thereby increasing the speed at which equilibrium is reached.^[3][4]

Although the macroscopic equilibrium concentrations are constant in time reactions do occur at the molecular level. For example, in the case of ethanoic acid dissolved in water and forming ethanoate and hydronium ions,

CH₃CO₂H + H₂O ⇌ CH₃CO₂⁻ + H₃O⁺

a proton may hop from one molecule of ethanoic acid on to a water molecule and then on to an ethanoate ion to form another molecule of ethanoic acid and leaving the number of ethanoic acid molecules unchanged. This is an example of dynamic equilibrium. Equilibria, like the rest of thermodynamics, are statistical phenomena, averages of microscopic behavior.

Le Chatelier's principle (1884) is a useful principle that gives a qualitative idea of an equilibrium system's response to changes in reaction conditions. If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change. For example, adding more S from the outside will cause an excess of products, and the system will try to counteract this by increasing the reverse reaction and pushing the equilibrium point backward (though the equilibrium constant will stay the same).

If mineral acid is added to the ethanoic acid mixture, increasing the concentration of hydronium ion, the amount of dissociation must decrease as the reaction is driven to the left in accordance with this principle. This can also be deduced from the equilibrium constant expression for the reaction:

if {H₃O⁺} increases {CH₃CO₂H} must increase and {CH₃CO₂⁻} must decrease. The H₂O is left out as it is a pure liquid and its concentration is undefined.

A quantitative version is given by the reaction quotient.

J.W. Gibbs suggested in 1873 that equilibrium is attained when the Gibbs energy of the system is at its minimum value (assuming the reaction is carried out under constant pressure). What this means is that the derivative of the Gibbs energy with respect to reaction coordinate (a measure of the extent of reaction that has occurred, ranging from zero for all reactants to a maximum for all products) vanishes, signalling a stationary point. This derivative is usually called, for certain technical reasons, the Gibbs energy change.^[5] This criterion is both necessary and sufficient. If a mixture is not at equilibrium, the liberation of the excess Gibbs energy (or Helmholtz energy at constant volume reactions) is the “driving force” for the composition of the mixture to change until equilibrium is reached. The equilibrium constant can be related to the standard Gibbs energy change for the reaction by the equation

where R is the universal gas constant and T the temperature.

When the reactants are dissolved in a medium of high ionic strength the quotient of activity coefficients may be taken to be constant. In that case the concentration quotient, K_c,

where [A] is the concentration of A, etc., is independent of the analytical concentration of the reactants. For this reason, equilibrium constants for solutions are usually determined in media of high ionic strength. K_c varies with ionic strength, temperature and pressure (or volume). Likewise K_p for gases depends on partial pressure. These constants are easier to measure and encountered in high-school chemistry courses.

Dry cell

Dry cells do not have a fluid electrolyte. Instead, they use a moist electrolyte paste. Leclanché's cell is a good example of this, where the anode is a zinc container surrounded by a thin layer of manganese dioxide and a moist electrolyte paste of ammonium chloride and zinc chloride mixed with starch. The cell's cathode is represented by a carbon bar inserted on the cell's electrolyte, usually placed in the middle.

Leclanché's simplified half reactions are shown below:

The voltage obtained from the zinc-carbon battery is around 1.5 V.

Electrochemical cells

An electrochemical cell is a device that produces an electric current from energy released by a spontaneous redox reaction. This kind of cell includes the Galvanic cell or Voltaic cell, named after Luigi Galvani and Alessandro Volta, both scientists who conducted several experiments on chemical reactions and electric current during the late 18th century.

Electrochemical cells have two conductive electrodes (the anode and the cathode). The anode is defined as the electrode where oxidation occurs and the cathode is the electrode where the reduction takes place. Electrodes can be made from any sufficiently conductive materials, such as metals, semiconductors, graphite, and even conductive polymers. In between these electrodes is the electrolyte, which contains ions that can freely move.

The Galvanic cell uses two different metal electrodes, each in an electrolyte where the positively charged ions are the oxidized form of the electrode metal. One electrode will undergo oxidation (the anode) and the other will undergo reduction (the cathode). The metal of the anode will oxidize, going from an oxidation state of 0 (in the solid form) to a positive oxidation state and become an ion. At the cathode, the metal ion in solution will accept one or more electrons from the cathode and the ion's oxidation state is reduced to 0. This forms a solid metal that electrodeposits on the cathode. The two electrodes must be electrically connected to each other, allowing for a flow of electrons that leave the metal of the anode and flow through this connection to the ions at the surface of the cathode. This flow of electrons is an electrical current that can be used to do work, such as turn a motor or power a light.

A Galvanic cell whose electrodes are zinc and copper submerged in zinc sulfate and copper sulfate, respectively, is known as a Daniell cell.

Half reactions for a Daniell cell are these:

In this example, the anode is zinc metal which oxidizes (loses electrons) to form zinc ions in solution, and copper ions accept electrons from the copper metal electrode and the ions deposit at the copper cathode as an electrodeposit. This cell forms a simple battery as it will spontaneously generate a flow of electrical current from the anode to the cathode through the external connection. This reaction can be driven in reverse by applying a voltage, resulting in the deposition of zinc metal at the anode and formation of copper ions at the cathode.

To provide a complete electric circuit, there must also be an ionic conduction path between the anode and cathode electrolytes in addition to the electron conduction path. The simplest ionic conduction path is to provide a liquid junction. To avoid mixing between the two electrolytes, the liquid junction can be provided through a porous plug that allows ion flow while reducing electrolyte mixing. To further minimize mixing of the electrolytes, a salt bridge can be used which consists of an electrolyte saturated gel in an inverted U-tube. As the negatively charged electrons flow in one direction around this circuit, the positively charged metal ions flow in the opposite direction in the electrolyte.

A voltmeter is capable of measuring the change of electrical potential between the anode and the cathode.

Electrochemical cell voltage is also referred to as electromotive force or emf.

A cell diagram can be used to trace the path of the electrons in the electrochemical cell. For example, here is a cell diagram of a Daniell cell:

First, the reduced form of the metal to be oxidized at the anode (Zn) is written. This is separated from its oxidized form by a vertical line, which represents the limit between the phases (oxidation changes). The double vertical lines represent the saline bridge on the cell. Finally, the oxidized form of the metal to be reduced at the cathode, is written, separated from its reduced form by the vertical line. The electrolyte concentration is given as it is an important variable in determining the cell potential.

Electrochemistry

Electrochemistry is a branch of chemistry that studies chemical reactions which take place in a solution at the interface of an electron conductor (a metal or a semiconductor) and an ionic conductor (the electrolyte), and which involve electron transfer between the electrode and the electrolyte or species in solution.

If a chemical reaction is driven by an external applied voltage, as in electrolysis, or if a voltage is created by a chemical reaction as in a battery, it is an electrochemical reaction. Chemical reactions where electrons are transferred between molecules are called oxidation/reduction (redox) reactions. In general, electrochemistry deals with situations where oxidation and reduction reactions are separated in space or time, connected by an external electric circuit to understand each process.

Summary

Chemistry is the scientific study of interaction of chemical substances^[3] that are constituted of atoms or the subatomic particles: protons, electrons and neutrons.^[4] Atoms combine to produce molecules or crystals. Chemistry is often called "the central science" because it connects the other natural sciences such as astronomy, physics, material science, biology, and geology.^[5][6]

The genesis of chemistry can be traced to certain practices, known as alchemy, which had been practiced for several millennia in various parts of the world, particularly the Middle East.^[7]

The structure of objects we commonly use and the properties of the matter we commonly interact with, are a consequence of the properties of chemical substances and their interactions. For example, steel is harder than iron because its atoms are bound together in a more rigid crystalline lattice; wood burns or undergoes rapid oxidation because it can react spontaneously with oxygen in a chemical reaction above a certain temperature; sugar and salt dissolve in water because their molecular/ionic properties are such that dissolution is preferred under the ambient conditions.

The transformations that are studied in chemistry are a result of interaction either between different chemical substances or between matter and energy. Traditional chemistry involves study of interactions between substances in a chemistry laboratory using various forms of laboratory glassware.

A chemical reaction is a transformation of some substances into one or more other substances.^[8] It can be symbolically depicted through a chemical equation. The number of atoms on the left and the right in the equation for a chemical transformation is most often equal. The nature of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws.

Energy and entropy considerations are invariably important in almost all chemical studies. Chemical substances are classified in terms of their structure, phase as well as their chemical compositions. They can be analysed using the tools of chemical analysis, e.g. spectroscopy and chromatography.

Chemistry is an integral part of the science curriculum both at the high school as well as the early college level. At these levels, it is often called "general chemistry" which is an introduction to a wide variety of fundamental concepts that enable the student to acquire tools and skills useful at the advanced levels, whereby chemistry is invariably studied in any of its various sub-disciplines. Scientists, engaged in chemical research are known as chemists.^[9] Most chemists specialize in one or more sub-disciplines.

Chemistry

Chemistry (from Egyptian kēme (chem), meaning "earth"^[1]) is the science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions.^[2] It is a physical science for studies of various atoms, molecules, crystals and other aggregates of matter whether in isolation or combination, which incorporates the concepts of energy and entropy in relation to the spontaneity of chemical processes. Modern chemistry evolved out of alchemy following the chemical revolution (1773).

Disciplines within chemistry are traditionally grouped by the type of matter being studied or the kind of study. These include inorganic chemistry, the study of inorganic matter; organic chemistry, the study of organic matter; biochemistry, the study of substances found in biological organisms; physical chemistry, the energy related studies of chemical systems at macro, molecular and submolecular scales; analytical chemistry, the analysis of material samples to gain an understanding of their chemical composition and structure. Many more specialized disciplines have emerged in recent years, e.g. neurochemistry the chemical study of the nervous system (see subdisciplines).

Chemical reaction

A chemical reaction is a process that always results in the interconversion of chemical substances.^[1] The substance or substances initially involved in a chemical reaction are called reactants. Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants. Classically, chemical reactions encompass changes that strictly involve the motion of electrons in the forming and breaking of chemical bonds, although the general concept of a chemical reaction, in particular the notion of a chemical equation, is applicable to transformations of elementary particles, as well as nuclear reactions. Different chemical reactions are used in combination in chemical synthesis in order to get a desired product. In biochemistry, series of chemical reactions catalyzed by enzymes form metabolic pathways, by which syntheses and decompositions ordinarily impossible in conditions within a cell are performed.