Scientific Method

Apologia’s secondary science textbooks usually have a section on the scientific method.  I prefer to teach experimental design.  I emphasize hands-on activities and labs because kids learn more.  Use activities for instruction.  Start with the Rainbow Lab.  What factors or variables should be controlled or kept the same?  Ask the kids before the lab.  Answers may include drops of pigment, water temperature, all tap or distilled water—even same sized graduated cylinders for measures.  Look at Scientific Method Using Alka-seltzer lab.  Instead of following the directions precisely, start with Alka-seltzer tablets, beakers and water.  Before lab, ask kids how to manipulate the rate the tablets dissolve.  Let the class discuss the method, say water temperature, and ask which variables should be controlled in order to test one variable temperature. See the difference?  The kids should tell you to keep water volume, type of container, and mass of the tablet the same.  

I use this approach often.  Here is another example: DNA Extraction Lab.  First the kids follow the directions.  Next, I issue a challenge.  Does the type of detergent matter?  Many recipes recommend Dawn dish soap.  Would soft soap, laundry detergent, or shampoo work?  How will we know which detergent works best? (Which method produces the greatest amount of DNA?). There are other factors or variables to manipulate: coarse or fine salt, iodized or noniodized salt, 70% or 90% rubbing alcohol, rubbing alcohol or ethyl alcohol, cold alcohol or room temperature alcohol.  Remind kids to test one variable at a time.  

Don’t get hung up trying to formulate ‘if than’ statements.  Instead identify the single independent variable to test and derive a hypothesis.  For example, Dawn dish soap will produce the most DNA.  Then run equal amounts of every brand or soap you can find in your house.  Here is a simple scientific method template which ironically is NOT ham-strung by rigid adherence to the scientific method.