01Evidence and balancing
Evidence of a chemical reaction: color change, gas, precipitate, temperature change. Balanced equations conserve atoms and charge.
Coefficients give mole ratios, never mass ratios.
02Notebook box
Balance metals, then nonmetals, then H, then O last.
Worked example: C₃H₈ + 5O₂ → 3CO₂ + 4H₂O.