Oh no! The power went out! (We are playing pretend for a moment, just go with it)
Hold on, I am going to grab my flashlight. Oh geez… the flashlight won’t turn on. What’s wrong with it?
I know what you are thinking: it’s probably the batteries. Okay, I will change the batteries, I am sure I have some around here. One moment please.
Okay, there we go, the batteries are changed. Let’s try it again! Oh for crying out loud, it's still not working!
It must be the bulb. One sec, I will switch out the bulb.
Okay great we are back in business!! Okay, onto the blog post….
That situation may be fairly familiar to students. They make an observation (like the flashlight not working), and ask themselves a question (why isn’t it working). They come up with a likely reason, or hypothesis, (the batteries) and go to test their thinking (switching the batteries). They get some results (the flashlight still doesn’t work) and they are able to make a conclusion (the batteries weren’t the problem). Without realizing it, students have just walked through the entire scientific method. It’s a relatable demonstration you can use in the classroom to illustrate the process before you even cover the vocabulary. (I’m sure there are other great examples of demos like this, we would love to hear them in the comments!).
It’s the beginning of the school year and we know many of you science teachers are going to be covering the scientific method with your students. We have got you covered with some FREE RESOURCES!
Vocabulary can be tricky! It is important that students know the difference between the types of variables. A variable is something that changes. The independent variable is what is changing on purpose. If a scientist is trying to determine which color of light is best for plant growth they are going to purposefully change the colors of light for the different plants. The dependent variable is what changes in response to the independent variable. In our plant example, the plants may have different growth rates because of the different lights. The growth rate or height would be the dependent variable. This is inevitably what the scientist is recording on their data table. The control variables are all the the things that could change but are kept the same. In this case it would be aspects like the amount of water, how often the plants are watered, the temperature of the environment, and the type of plant.
The idea of a control group can skew more high school level but it is an important step of the experimental design process and can speak to the validity of the results. For example, in our beloved Liver Lab, we always test the liver in plain water. This is a negative control because we expect no reaction. If the liver DID bubble in the water, that would suggest there is something wrong with the experiment. Maybe the water was contaminated? Maybe the cup? It would indicate that the experiment should be repeated.
Students can get tripped up in the vocabulary of the different variables and different steps of the scientific method. We have made several different resources to help your students along the way:
Download a free PDF of our Scientific Method Poster!
Be sure to check out some of our previous posts for lab ideas that ask students to pick their own variables and design their own experiment!
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