Reflection: Rigor Reaction Rates and Equilibrium Computer and Graphing Practice - Section 4: Elaborate Part II


As I looked over student work on the graphing reaction rates paper I noticed that there were quite a few mistakes and confusions.  The following three examples of students work highlight these.

In this first example (student 1) the student graphed the value for 0.1 not 1.0 at time 0.  Also this student did not include units in their answer.

In this second example (student 2) the student added the concentration values instead of subtracting them when determining reaction rate.

In this third example (student 3) the student subtracted the values incorrectly and did not answer the final question in terms of where the rate was faster. 

Next year I will make sure to do a better job of explaining to students how to figure out reaction rates with doing an example from the middle of the graph.  I may say something like, "to figure out the rate we need to find the change in concentration over change in time.  An example of this is if we want to find the rate from time 60 to 80.  What we will do is take the change in concentration which would be the value at 80s which is .61M minus the value at 60s which is .69M to give us negative .08 M.  We will then take 80s minus 60s which gives us 20 seconds.  Then if we take -.08M divided by 20s we get the answer of negative .004 M/s."

  Rigor: Difficulty with Reaction Rate Calculations
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Reaction Rates and Equilibrium Computer and Graphing Practice

Unit 8: Unit 9: Reaction Rates and Equilibrium
Lesson 4 of 6

Objective: Student will be able to describe, model and diagram chemical reactions and explain what happens to systems in equilibrium when stressed as evidenced by computer and graphing activities.

Big Idea: In equilibrium systems, reactants and products have specific concentrations and energy. When equilibrium reactions are stressed the effects can be predicted using Le Chatelier's Principle.

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Science, Chemistry, reaction rates, Reaction Rates and Equilibrium, Equilibrum, collision theory, Le Chatelier's Principle
  95 minutes
phet reactions lab
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