Chemical change

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In a chemical change, 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. Some 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.

Chemical changes are happening all the time. There are several different types of chemical change, including: synthesis, decomposition, single displacement, double displacement, neutralization, precipitation, combustion, redox and wood burning.

A primary example of a chemical change is the combustion of methane to produce carbon dioxide and water.

Other examples of chemical changes are:

• Mixing an acid with a base, producing water and a salt.
• Photosynthesis - a process in which carbon dioxide and water are changed into sugars by plants.
• Cracking heavy hydrocarbons to create lighter hydrocarbons (part of the process of refining oil).
• Cooking examples: popcorn, cake, pancakes, and eggs
• Oxidation examples: rust or tarnishing
• Ripening examples: bananas, tomatoes

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

• Change of odor
• 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).

External links

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

A simple chemical change can cause a big change in chemistry.