The 5-Minute Pre-Lab Routine That Eliminates Student Confusion

Have you ever been here?  You explain your lab perfectly.  The students are told the process, the calculations, the safety concerns.  You have given an Oscar-worthy performance.  And within 2 minutes of the start of the lab, a student asks, “Where do I get the grams of sodium hydroxide?” 

What!

Where else would you get the grams of sodium hydroxide?  Are you serious?  Didn’t you listen to my explanation? 

And the answer is they did listen to your instructions, but they didn’t engage with them.

Using this simple system for lab instructions will make the students engage with lab before they set foot in the lab.  And therefore reduce (not eliminate, unfortunately) those obvious questions.  Here is the 5-minute pre-lab process that will change the success of your students.

Start with the Goal

The students need some context.  Give them a brief summary of the goal of the lab so that they can think about it.  The goal of this lab is to calculate the percent yield of copper.  The goal of this lab is calculate the specific heat capacity of an unknown metal.  The goal of this lab is to calculate the enthalpy of reaction using Hess’ Law.

Add a “By”

Then give them a “by” statement.   The goal of this lab is to calculate the percent yield of copper by reacting zinc powder with aqueous copper (II) nitrate and filtering the products.

This short phrase gives them the overview of how they are going to accomplish the goal.  This helps them anchor themselves in the methods. 

Students Explain the Data Table

This is the change that made the biggest difference on lab day.  Have the students turn to the data table.  Without your help, have them go column by column and use a highlighter to highlight the measurements.  These are the things that they will have to measure during the lab.  Then they circle the columns that will be calculated.  Every row has a designation.  Measure or calculate. 

How to Measure

The students then go through all the highlighted columns and describe how they will get that number.  If one of the columns is “Mass of zinc”, the students decide that they will have to get a weighing boat, zero it, and weigh the zinc on a scale.  Is that utterly obvious to you and me?  Of course.  And once they say it out loud with their lab partner, it is obvious to them too!  The biggest difference is that THEY thought up the method.  They decided where the value will come from.  Therefore, THEIR brain was engaged in making the decision.  That is different than listening to your Magnum Opus before the start of the lab.

How to Calculate

Now the students go through all the circled columns that need to be calculated.  Above each circled item, they write a note about what equation or calculation to do.  Even if it feels obvious.  This gives their brains an opportunity to see where the math is going.  It also crystalizes that some things will be measured in the lab and others will not.  I just finished a fuel value lab in which they only had to measure 3 of the 10 columns.  The rest were calculated.  By prepping their thinking, they are so much more efficient in the lab. 

Students Define Errors and Dangers

The final step that the students take is anticipating errors and dangers.  You can ask some guiding questions here.  In my lab I asked, “Which of the three is the most likely measurement to forget?”  They correctly answered the initial temperature.  And since they identified it as an easy error to make, they were less likely to make it.

I also have them identify potential dangers.  If the students are the ones to recognize that the metal will be hot, the sodium hydroxide is caustic, the fumes might smell bad, then the students will be better equipped to avoid the dangers.  Again, some guiding questions will be helpful.

In just a few minutes, the students have gone from passive observers of the lab instructions to engaged creators of the process.  The errors are significantly reduced.  Students are better able to solve problems for themselves.  Safety is improved.  All because the teacher shut their mouth, and the students engaged their brains.

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