Combustion, an example of a chemical change.

A chemical change is a process in which reactants are changed into one or more different products. A chemical change occurs whenever compounds are formed or decomposed. During this reaction, there is a rearrangement of atoms that makes or breaks chemical bonds. This change is usually not reversible. Image File history File links Beschreibung: Match Fire Wood Quelle: Fotografiert im Dezember 2004 Fotograf: Heidas Wikipedia account All pictures please use this discussion page File links The following pages link to this file: Match ... Image File history File links Beschreibung: Match Fire Wood Quelle: Fotografiert im Dezember 2004 Fotograf: Heidas Wikipedia account All pictures please use this discussion page File links The following pages link to this file: Match ... This article is about the chemical reaction combustion. ... A reactant or reagent is any substance initially present in a chemical reaction. ... Look up chemical compound in Wiktionary, the free dictionary. ... Properties For other meanings of Atom, see Atom (disambiguation). ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ...

There are several different types of chemical change. These include synthesis, decomposition, single displacement, double displacement, neutralization, precipitation and redox. In chemistry, chemical synthesis is purposeful execution of chemical reactions in order to get a product, or several products. ... Decomposition means the separation of a substance into two or more substances that may differ from each other and from the original substance. ... It has been suggested that this article or section be merged with Single replacement scheme. ... In a chemical double displacement reaction (double replacement, metathesis, or ion exchange reactions) two compounds swap ions, effectively displacing each other to form two new compounds, thus the name. ... Neutralization is a chemical reaction, also called a water forming reaction, in which an acid and a base or alkali (soluble base) react and produce a salt and water. ... Illustration of a redox reaction Redox (shorthand for oxidation/reduction reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. ...

An elementary example of a chemical change is the combustion of methane to produce carbon dioxide and water: This article is about the chemical reaction combustion. ... Methane is a chemical compound with the molecular formula . ... Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ...

CH₄ + 2O₂ → CO₂ + 2H₂O

Other examples of chemical changes are:

• Burning a log of wood
• Mixing an acid with a base, producing water and a salt
• Melting a piece of plastic

Changes in state but not chemical composition are not considered chemical changes. For example, while boiling water involves a change in temperature and the release of a gas (water vapor), a chemical change did not take place. For other uses, see Acid (disambiguation). ... Acids and bases: Acid-base extraction Acid-base reaction Acid dissociation constant Acidity function Buffer solutions pH Proton affinity Self-ionization of water Acids: Lewis acids Mineral acids Organic acids Strong acids Superacids Weak acids Bases: Lewis bases Organic bases Strong bases Superbases Non-nucleophilic bases Weak bases edit In... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... A magnified crystal of salt In chemistry, salt is a term used for ionic compounds composed of positively charged cations and negatively charged anions, so that the product is neutral and without a net charge. ... In the physical sciences, a state of matter is one of the many ways that matter can interact with itself to form a macroscopic, homogenous phase. ... For other uses, see Temperature (disambiguation). ... Gas can also refer to gasoline and natural gas and also hydrogen. ... Water vapor or water vapour (see spelling differences), also aqueous vapor, is the gas phase of water. ...

The following can indicate that a chemical change took place, although this evidence is not conclusive:

• Change of color (for example, silver to reddish-brown when iron rusts).
• Change in temperature or energy, such as the production (exothermic) or loss (endothermic) of heat.
• Change of form (for example, burning paper).
• Light, heat, or sound is given off.
• Formation of gases, often appearing as bubbles.
• Formation of precipitate (insoluble particles).
• The decomposition of organic matter (for example, rotting food).

In a chemical reaction bonds are broken and new bonds are formed between different atoms. This breaking and forming of bonds takes place when particles of the original materials collide with one another. When new substances are formed, a chemical change has occurred, and a chemical reaction has taken place. Note that, in a few cases, exothermic reactions may be hot enough to cause certain chemicals to also undergo a change in state; for example in the case of aqueous solutions, bubbles may not necessarily be newly produced gas but instead water vapor. For other uses, see Iron (disambiguation). ... In thermodynamics, the word exothermic describes a process or reaction that releases energy in the form of heat. ... In thermodynamics, the word endothermic describes a process or reaction that absorbs energy in the form of heat. ... For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another due to a difference in temperature. ... For other uses, see Light (disambiguation). ... This article is about audible acoustic waves. ... This article does not cite any references or sources. ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ...

See also

• Physical change
• Chemical reaction
• Chemical process
• Reactant

A physical change involves the change just in the physical body of the substance without changing its composition. ... For other uses, see Chemical reaction (disambiguation). ... In a scientific sense, a chemical process is a method or means of somehow changing one or more chemicals or chemical compounds. ... A reactant or reagent is any substance initially present in a chemical reaction. ...

References

• Zumdahl, Steve S. (2005), Chemical Principles (5 ed.), Houghton Mifflin, ISBN 0618372067

Houghton Mifflin Company is a leading educational publisher in the United States. ...

External links

• Definition of 'chemical change', wordnet.princeton.edu