- A compact notation for describing a chemical change. The formulas of the reactants are added together on the left hand side of the equation; the formulas of the products are added together on the right side. Coefficients are inserted before the formulas to ensure that the equation is balanced. The phase in which each substance is found is usually indicated in parentheses after each formula.
- 2H2(g) + O2(g) = 2H2O(g)
- This indicates that 2 moles of hydrogen gas combine with one mole of oxygen gas to produce two moles of steam.
See also: Molecular Equation.