The Effect of Concentration on the Rate of a Chemical Reaction




This video shows a classic lab examining the effect of concentration of reactants on the rate of a chemical reaction.  This video supports NGSS HS-PS1-5.

In this experiment solutions of sodium thiosulfate and hydrochloric acid are combined in a beaker.  The reaction produces a precipitate which eventually makes the liquid turn cloudy.  The reaction beaker is placed over a piece of paper with a letter "X" printed on it.  The reaction is said to have gone to completion when the "X" can no longer be seen through the liquid in the beaker.

I have used this video as a warm up or as a flipped lesson which has students make observations, record data about the reaction time for the trials, create a graph and form a conclusion about the effect concentration has on the speed of a chemical reaction.

This lab was originally published by Flinn Scientific as a Chem Fax!  Use this link to see the full description of the experiment.

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