A chemical reaction happens when one or more chemicals are changed into one or more other chemicals. Examples:
- iron and oxygen combining to make rust
- vinegar and baking soda combining to make sodium acetate, carbon dioxide and water
- things burning or exploding
- many reactions that happen inside living things
- electrochemical reactions when discharging or recharging batteries
Some reactions are fast, and others are slow. Some happen at different speeds, depending on temperature or other things. For example, wood does not react with air when it is cold, but if it is made hot enough, it will start to burn. Some reactions give out energy. These are exothermic reactions. In other reactions, energy is taken in. These are endothermic reactions.
Four basic types
In a synthesis reaction, two or more simple substances combine to form a more complex substance.
Another example is simple hydrogen gas combined with simple oxygen gas to produce a more complex substance, such as water.
A decomposition reaction is when a more complex substance breaks down into its more simple parts. It is thus the opposite of a synthesis reaction, and can be written as:
In a single replacement reaction, a single uncombined element replaces another in a compound; in other words, one element trades places with another element in a compound These reactions come in the general form of:
In a double replacement reaction, the anions and cations of two compounds switch places and form two entirely different compounds. These reactions are in the general form:
A thermite reaction using iron(III) oxide. The sparks flying outwards are globules of molten iron trailing smoke in their wake.
Antoine Lavoisier developed the theory of combustion as a chemical reaction with oxygen
Sodium chloride is formed through the redox reaction of sodium metal and chlorine gas
Ferrocene – an iron atom sandwiched between two C5H5 ligands
Solid heterogeneous catalysts are plated on meshes in ceramic catalytic converters in order to maximize their surface area. This exhaust converter is from a Peugeot 106 S2 1100
Chemical reaction for Kids. Kiddle Encyclopedia.