Science Fair Projects World

The Effect of Concentration on Reaction Rate


Determine how the concentration of reactants affects the rate of a chemical reaction.


  • Sodium thiosulfate
  • Hydrochloric acid (HCl)
  • Graduated cylinders
  • Beakers
  • Stopwatch
  • Notebook for observations


  1. Prepare different concentrations of sodium thiosulfate by diluting with water.
  2. Measure a specific volume of hydrochloric acid for each reaction.
  3. Add hydrochloric acid to the sodium thiosulfate solution and start the stopwatch.
  4. Observe and record the time it takes for the solution to turn cloudy.
  5. Repeat the experiment with different concentrations of sodium thiosulfate.
  6. Compare the reaction rates at different concentrations and draw conclusions about the effect of concentration on reaction rate.