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Chemical change
 
 
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In a chemical reaction, bond
Chemical bond

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....
s 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. Some exothermic
Exothermic

File:Explosion1.JPG In thermodynamics, the term exothermic describes a process or reaction that releases energy usually in the form of heat, but also in form of light , electricity , or sound....
 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.

Chemical changes are happening very often.






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In a chemical reaction, bond
Chemical bond

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....
s 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. Some exothermic
Exothermic

File:Explosion1.JPG In thermodynamics, the term exothermic describes a process or reaction that releases energy usually in the form of heat, but also in form of light , electricity , or sound....
 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.

Chemical changes are happening very often. When wood burns it is a chemical change. There are several different types of chemical change. These include synthesis
Chemical synthesis

In chemistry, chemical synthesis is purposeful execution of chemical reactions in order to get a product , or several products. This happens by physics and chemical manipulations usually involving one or more reactions....
, decomposition, single displacement
Single displacement reaction

A single-displacement reaction, also called single-replacement reaction, is when an element or ion moves out of one compound and into another....
, double displacement, neutralization, precipitation
Precipitation (chemistry)

Precipitation is the formation of a solid in a solution during a chemical reaction. When the reaction occurs, the solid formed is called the precipitate, and the liquid remaining above the solid is called the supernate....
 and redox
Redox

Redox describes all chemical reactions in which atoms have their oxidation number changed.This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide or the reduction of carbon by hydrogen to yield methane , or it can be a complex process such as the oxidation of sugar in the human body through a ser...
.

An elementary example of a chemical change is the combustion
Combustion

Combustion or burning is a complex sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames, appearance of light flickering....
 of methane
Methane

Methane is a chemical compound with the molecular formula . It is the simplest alkane, and the principal component of natural gas. Methane's bond angles are 109.5 degrees....
 to produce carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
 and water
Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
: Wood burning is also a chemical change.

Other examples of chemical changes are:
  • Burning a log of wood
    Wood

    Wood is an organic material; in the strict sense wood is produced as secondary xylem in the stems of woody plants, notably trees but also shrubs, etc....
    .
  • Mixing an acid
    Acid

    An acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion Activity greater than in pure water, i.e....
     with a base
    Base (chemistry)

    In chemistry, a base is most commonly thought of as an aqueous substance that can accept protons. A base is also often referred to as an alkali if OH- ions are involved....
    , producing water
    Water

    Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
     and a salt.
  • Photosynthesis
    Photosynthesis

    File:Seawifs global biosphere.jpgPhotosynthesis is a metabolic pathway that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight....
     - a process in which carbon dioxide and water are changed into sugars by plants.
  • Cracking
    Cracking (chemistry)

    In petroleum geology and chemistry, cracking is the process whereby complex organic compound molecules such as kerogens or heavy hydrocarbons are broken down into simpler molecules by the breaking of carbon-carbon chemical bond in the precursors....
     heavy hydrocarbons to create lighter hydrocarbons (part of the process of refining oil).
  • Cooking
    Cooking

    Cooking is the process of preparing food by applying heat, selecting, measuring and combining of ingredients in an ordered procedure for producing safe and edible food....
     examples: popcorn, cake, pancakes, and eggs
  • Oxidation examples: rust or tarnishing


The following can indicate that a chemical change took place, although this evidence is not conclusive:
  • Change of odour
  • Change of colour (for example, silver to reddish-brown when iron
    Iron

    Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
     rusts).
  • Change in temperature or energy
    Energy

    In physics, energy is a scalar physical quantity that describes the amount of Work_ that can be performed by a force. Energy is an attribute of objects and systems that is subject to a conservation law....
    , such as the production (exothermic
    Exothermic

    File:Explosion1.JPG In thermodynamics, the term exothermic describes a process or reaction that releases energy usually in the form of heat, but also in form of light , electricity , or sound....
    ) or loss (endothermic
    Endothermic

    In thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs energy in the form of heat. Its etymology stems from the Greek prefix endo-, meaning ?inside? and the Greek suffix ?thermic, meaning ?to heat?....
    ) of heat
    Heat

    In physics and thermodynamics, heat is any transfer of energy from one body or thermodynamic system to another due to a difference in temperature....
    .
  • Change of form (for example, burning paper).
  • Light
    Light

    Light, or visible light, is electromagnetic radiation of a wavelength that is Visible spectrum to the human eye , or up to 380?750 nm. In the broader field of physics, light is sometimes used to refer to electromagnetic radiation of all wavelengths, whether visible or not....
    , heat, or sound
    Sound

    Sound is vibration transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a threshold of hearing to be heard, or the sensation stimulated in organs of hearing by such vibrations....
     is given off.
  • Formation of gases, often appearing as bubbles.
  • Formation of precipitate (insoluble particles).
  • The decomposition of organic matter (for example, rotting food).


See also

  • Physsxsgjgh7
  • Chemical reaction
    Chemical reaction

    A chemical reaction is a process that always results in the interconversion of chemical substances. The substance or substances initially involved in a chemical reaction are called reactants....
  • Chemical process
    Chemical process

    In a "Process " sense, a chemical process is a method or means of somehow changing one or more chemicals or chemical compounds. Such a chemical process can occur by itself or be caused by somebody....
  • Reactant
  • Exothermic reactions


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