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, such as photosynthesis
- 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[change | change source]
Synthesis[change | change source]
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.
Decomposition[change | change source]
CaCO3 —> CaO + CO2
Single replacement[change | change source]
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:
Double replacement[change | change source]
Equations[change | change source]
A chemical reaction is being displayed by an equation:
- Here, A and B react to C and D in a chemical reaction.
- This is an example of a combustion reaction.
Related pages[change | change source]
Other websites[change | change source]
- Rates of reaction Archived 2007-03-05 at the Wayback Machine
- Online chemical equation balancer Balances equation of any chemical reaction (full or half-cell) in one click.