So I'm teaching a lesson to seventh grade kids about why we need to have controlled variables in an experiment. I have the bulk of it figured out but I want to start out the lesson with examples of experiments where there is obviously no control and it's throwing the entire experiment off course, but I'm having some trouble coming up with any ideas. When I think about it, controls are always obvious and don't do much except create a framework for what's going on and they're usually unnoticeable and boring (especially in the eyes of seventh graders) if you're not conducting the experiment.
So, what are some examples of experiments where there's no control and it's severely altering the experiment?
>Brainlets like OP are teaching the next generation
Keeping it a 7th grade level, tell them that you want to measure the amount of a product in a test tube by measuring its height.
(Not sure what country/curriculum, but make it something simple like a precipitate)
Show them that, when repeating the experiment, if you don't measure the reactants that the product will vary in size each time.
Even if you don't need it, just whack out a bunsen burner so they're not bored.
Your conception
>>7967705
This isn't quite engaging enough but thanks for the input
I just figured something out, though. I'm using a train tank implosion and an episode of Mythbusters to show how not to conduct an experiment
>>7967694
maybe tell them about making spectral measurements of colors before any experiments, since even the slightest lightray might contaminate the sample?
Maybe read into photo developing techniques which require the abscence of certain wavelenghts (your controlled variables) in order to work with certain materials.
if you want to make a cyanotype the film is not allowed to see daylight before being properly sealed.
