Chemical reaction: definition in chemistry
Chemical reaction: A process in which one or more substances (reactants) are changed into new substances (products) by breaking and forming chemical bonds.
In a reaction, atoms are rearranged but never created or destroyed, so mass is conserved and equations must balance. Signs that a reaction has happened include a color change, gas bubbles, a precipitate, light or a change in temperature. Reactions are often grouped into types such as combination, decomposition, displacement, combustion, neutralization and redox.
Examples
- Iron rusting in damp air
- Baking soda and vinegar fizzing as carbon dioxide forms
- Silver tarnishing as it reacts with sulfur compounds in air
- Bread browning in a toaster
On the periodic table
An element's position helps predict how it reacts: metals on the left tend to give up electrons, nonmetals on the right tend to gain them, and the noble gases rarely react at all.