Understanding How Substances Change

Reaction Types

Chemical reactions can be broadly classified into several types based on the changes they involve. Synthesis reactions combine two or more reactants to form a single product (A + B → AB). Decomposition reactions break down a single reactant into simpler products (AB → A + B). Exchange reactions involve the transfer of one or more atoms between reactants.

A + B → AB; AB → A + B

Balancing Chemical Equations

The law of conservation of mass dictates that matter cannot be created or destroyed in a chemical reaction. Therefore, the number of atoms of each element must be equal on both sides of a balanced equation. This ensures that the equation accurately represents the reaction.

2H₂ + O₂ → 2H₂O

Reaction Mechanisms

A reaction mechanism describes the step-by-step sequence of elementary reactions that occur during a chemical process. Each step involves the formation of one or more intermediate species. The overall balanced equation represents the net result of these individual steps.

Step 1: A + B → C; Step 2: C + D → E

Factors Affecting Reaction Rates

The speed at which a chemical reaction proceeds is influenced by several factors, including temperature, concentration of reactants, and the presence of catalysts. Increasing temperature generally increases reaction rates due to increased molecular kinetic energy.

Rate ∝ Concentration; Rate ∝ 1/Pressure (for gases)

Frequently asked questions

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