Reaction Rates
Middle School
Definition
How quickly a chemical reaction proceeds, measured by how fast reactants are used up or products are formed. The rate is affected by factors such as temperature, concentration, surface area, and the presence of a catalyst.
Worked examples
Increasing temperature from \(20^\circ\)C\(\) to \(40^\circ\)C\(\) doubles the rate at which hydrogen peroxide decomposes into water and oxygen.
Higher temperature means faster-moving particles collide more often and with more energy, speeding up the reaction.
Adding manganese dioxide catalyst to hydrogen peroxide dramatically speeds up oxygen release without being consumed.
A catalyst lowers the activation energy, letting the reaction proceed much faster at the same temperature.
Powdered zinc reacts with hydrochloric acid faster than a single zinc strip of the same mass.
Greater surface area exposes more reactant particles to collision, increasing the reaction rate.
Common mistakes
- Catalysts increase the yield of product formed → Catalysts speed up the reaction but do not change the amount of product A catalyst affects how fast equilibrium is reached, not the position of equilibrium or total yield.
- Concentration only matters for reactions in solution → Concentration (or pressure for gases) affects rate in any phase where particles can collide Gas reactions speed up when pressure increases because particles are closer together and collide more often.
- All reactions go faster at higher temperature by the same amount → Temperature sensitivity varies; each reaction has its own activation energy Reactions with high activation energy speed up more dramatically with temperature than low-activation-energy reactions.
Where you'll use it next
You'll apply reaction rates when studying chemical equilibrium, enzyme kinetics in biology, industrial process optimization, and environmental chemistry topics like ozone depletion and combustion.
See also
Rate of reactionCatalystActivation energyChemical reactionLe Chatelier's principleTemperature Effects
Reviewed by Pat Cheng, M.Ed. — StudyPug Curriculum Lead · Last updated June 6, 2026