What is Chemical change?
[[File:NaturalFireplace.jpg|thumb|250px|Burning wood is an example of a chemical change that is not reversible]] A '''chemical change''' ('''chemical reaction''') is a change of materials into other [[materials]] with different [[properties]]. Chemical changes occur when a substance combines with another to form a new substance, or, chemical decomposition into two or more different substances. These processes are called [[chemical reaction]]s. Burning of [[wood]] is a chemical change as new substances which cannot be changed back (e.g. [[carbon dioxide]]) are formed. For example, if wood is burned in a fireplace, there is not wood anymore but ash. Other examples include burning of a [[candle]], rusting of [[iron]], baking a cake, etc. Special details that describe how a chemical change takes place are called chemical properties. Compare: [[physical change]]. The [[opposite]] of a chemical change is a physical change. Physical changes are a change in which no new substances are formed, and the substance which is changed is the same. For instance, if a stick of wood is broken, there is still a stick of wood; it is just broken. More examples include changes of shape, changes of states, passing electricity through a copper wire, breaking of wood, shattering of glass, pouring of water, etc. Special details which do not change in a substance without new substances being formed are called physical properties. [[Category:Chemical reactions]]