In a chemical reaction, the substances that react together are called reactantsSubstances present at the start of a chemical reaction. and the substances that are made are called productsSubstances formed in a chemical reaction..
Word equations
All reactions can be represented in word equationsAn equation in which only the names of the reactants and products are used to model a reaction., which must contain an arrow (鈫).
reactants 鈫 products
For example, when heated, green copper(II) carbonate decomposes into black copper(II) oxide and colourless carbon dioxide gas.