Exploring Controlled Experiments (Part 2/2)

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SWBAT identify factors of a controlled experiment.

Big Idea

Investigation versus experimentation -- students learn the difference between "just messing around" and designing an experiment.


"When are we going to do an experiment?" This is a common refrain in middle school science. An important feature of science instruction is to help students understand that there is a distinct difference between "messing around in the lab", "randomly mixing chemicals together", "blowing things up" and actually planning an investigation that results in meaningful and accurate data. The trick is that messing around just sounds like so much fun!

This is part two of the lesson on Exploring Controlled Experiments -- an introduction to how to plan an investigation individually and collaboratively, and within that experimental design to:

  1. Identify independent and dependent variables and controls
  2. Tools needed to do the information/observations/data gathering
  3. How measurements are recorded
  4. How many data are needed to support a claim (SP3).  

In this practice, students also explore the nature of scientific concepts such as: "Scientific Investigations Use a Variety of Methods" and "Scientific Knowledge is Based on Empirical Evidence". Without controlled experiments and the various approaches to design those experiments, students' data become less empirical and more muddled, making if more difficult to answer "Questions About the Natural and Material World". The basis for controlled experiments rests on the cross-cutting concept of Cause and Effect. By exploring variables, students recognize that cause and effect relationships may be used to predict phenomena.

The Exploring Controlled Experiments series of lessons is an investigation that including lessons taught over the span of 2 or more days or equivalent block periods. To help manage the magnitude of this activity, you will find the project split into 2 parts. This lesson works in conjunction with Exploring Scientific Methods as well.

  • Part 1 includes the ENGAGE and EXPLORE components of the lesson; Time: 1 50-minute lessons or equivalent block periods. 
  • Part 2 includes the EXPLAIN, EXTEND and EVALUATE components of the lesson; Time: 1 - 2 50-minute lessons or equivalent block periods.


50 minutes

This stage of the lesson is the continuation from Part 1, which includes the ENGAGE and EXPLORE components of the lesson; Time: 1 50-minute lessons or equivalent block periods.

The EXPLAIN stage provides students with an opportunity to communicate what they have learned so far and figure out what it means.  To explain what students know, they revise and/or complete the first page of the Controlled Experiments Student Handout. An example of this page can be viewed here: Controlled Experiments Student Work 1.

This stage of the lesson presents a great place for a quick formative assessment. As students progress, I check for understanding before they move on to the analysis part of the activity. Using the questions provided in the "EXPLORE" stage of this lesson, students explain what they understand so far. This formative assessment allows me to make immediate interventions if students are confused about the basic factors and importance of those factors to controlled experiments. This is a specific way to assess students understanding of the cause and effect Crosscutting Concept (CCC).

Once students complete the first page, they move on to analyze simple Controlled Experiment Examples to see if they can apply their new understanding to the construction of "controlled experiments graphic organizers" (found on pages 2 -3 of Controlled Experiments Student Handout). This activity represents a step up in terms of complexity as suggested in the Revised Bloom's Taxonomy since students are applying their understanding of the concept while analyzing these simplified controlled experiments.

As students analyze, they are able to check their progress using Controlled Experiments Student Handout Notes and Answer Key.

Teacher Note: The analysis of the controlled experiments activity may benefit from an "I-We-You" progression prior to independent work. (Here's more about the I Do, We Do, You Do strategy.) Often, during this activity, rather than intervening with the whole class to model the analysis process with a gradual release of control to independent work, I will use the intervention with a small group as I recognize which students need additional help. The up-side to using the strategy with small groups is that it allows other students to work at their own pace, self-assess as they go, and progress on to the EXTEND stage of the lesson if they have time.


The EXTEND stage allows students to apply new knowledge to a novel situation. The novel situation is the creation of new, creative, and fun controlled experiments that can also be used to practice analyzing, for use as warm up activities, or for quiz questions.

Students create these novel controlled experiments on page 4 of the Controlled Experiments Student Handout. As can be seen in the Student Generated Quiz Questions and Controlled Experiments Student Work, the students have fun with this extension.

By composing these new experiments, students must draw on what they have learned in order to create experiments that "work" in terms of the required factors in a controlled experiment.


10 minutes

The EVALUATION stage is for both students and teachers to determine how much learning and understanding has taken place. I've found that understanding controlled experiments can be a difficult concept for middle school students. For this reason, after this initial lesson, I use the Controlled Experiments Mini Lessons over the course of a week or so to help students who need a more structured approach to understanding how to analyze an experiment. For students who "test out" of the concept and have moved on to completing extensions (as explained in the EXTEND section), they use this warm up time to work on their extensions or "student teach" the warm up.

In order to "test out", students analyze the experiment on slide 12 of the Controlled Experiments Mini Lessons or any of the Student Generated Quiz Questions on a blank experimental analysis graphic organizer (found on pages 2 -3 of Controlled Experiments Student Handout). This can be completed as students are ready or as an entire class. The following video is one that I use to help students understand the reasoning for each answer:

As noted earlier, this concept often requires additional time to relearn and reassess. For strategies for using technology to help the relearning process, check out the reflection for this section: Using Technology to Assist Relearning.