After the students' lab doesn't work, ask the students to consider what might have gone wrong. In the Rate of Reaction Lab, we all expected (including me) the chalk and vinegar to react. When there is not any evidence of a reaction, ask the students to speculate what could be the case for this? We considered the reactants (chalk and vinegar) and discussed the procedure.
Begin a discussion about experimental error. Introduce the topic but tell students that in place of a lab report, they will write a brief report
about experimental error based on research they do. I required at least 50 words but this will depend on your students. They should consider the following for their report.
What is experimental error?
What are the various factors that can cause experimental error?
When students have turned in their reports and the instructor has has a chance to read them over, return to the topic briefly during class. Focus on the fact that experimental error will cause inaccuracy in the results and that scientists must ALWAYS consider experimental error when analyzing and evaluating results. Give examples from your experience or science projects your students have done. Talk about the possibility of human error, equipment malfunctioning, etc.