Reactants vs Products: What's the Difference?
Every chemical equation is really a tiny before-and-after story. The trouble is that "before" and "after" have intimidating names — reactants and products — and it's easy to mix up which is which. Here's the simple rule that makes it stick. The short answer: reactants are the starting substances you begin a reaction with — they sit on the left of the arrow. Products are the new substances the reaction makes — they sit on the right of the arrow. The arrow (→) always points from reactants to products, meaning "turns into." Quick comparison at a glance Feature Reactants Products What they are Starting substances Substances formed Side of the arrow Left Right When they exist Before the reaction After the reaction During the reaction Used up (consumed) Built up (created) Arrow direction Arrow points away from them Arrow points toward them Example (burning carbon) C and O₂ CO₂ The whole idea lives in tha...