Students created testable questions and identified the variables for this experiment in the lesson Student Designed Lab: Testable Questions.
At this point, students are ready to begin the formal planning of an experiment. Students are familiar with conducting experiments, but most students have limited experience with the actual designing of an experiment. Most students will want to rush through this process to get to the fun part - conducting the experiment. It is extremely important that students understand the importance of good planning and that poor experimental design leads to poor data. Additionally, this builds up students' skills for Science Practice 3: Planning and Carrying Out Investigations, specifically the following:
When students enter the room, The Plant Experiment Scenario will be projected on the board. Students can work alone or with their table partners to read the experimental situation and answer the questions that follow.
Common Core Connection: Students are asked to write an accurate summary of the experiment presented in the scenario (science literacy standard RST.6-8.2). Clearly stating their ideas into their own words, including science vocabulary, is a challenging skill that students must practice to be able to master. I incorporate writing for a variety of purposes (research, reflection, revision) as much as possible into my lessons. (W.8.10)
Also, students have not yet been exposed to control and experimental groups. However, most students completed a science fair style experiment toward the end of their 7th grade year so many of the students will know what these are and will be able to identify them from the scenario.
As students are working on the questions, I walk around and offer support and assistance to students who are struggling. When groups have finished, we go over their answers as a class. I really like to focus on their ideas for improving the experiment and having students explain why the believe their ideas will make the experiment better. This provides students with more practice justifying their ideas.
Students have already created a testable question and identified the independent and dependent variables for the object they chose and wrote these in their science journals. To assist students in keeping all of their work in one location, I provide students with guided notes. I typically have students paste this into their science journal but they could just as easily copy it down.
Students now add a list of variables they must control/keep constant for the duration of their experiment. I instruct students that they should have a list of between 7-10 controlled variables for their experiment. As they finish, I review their list and initial it to indicate approval. I find that students focus more seriously on the task when I tell them it must be approved before they can move ahead.
Common Core Connection: SL.8.4 Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher-led) with diverse partners on grade 8 topics, texts, and issues, building on others' ideas and expressing their own clearly.
As students are discussing, I am walking around making sure that all students are participating in the discussion, everyone is actively listening to their group members and adding to or tweaking other's ideas. I offer prompts and ask students to elaborate on their thinking by asking questions such as "Can you tell me more about why..." or "What would happen if..." or "How would you improve...".
After approval, students work together to create their formal testing procedure. I explain to each group that they are not only writing their procedure for themselves, but for a future audience that must be able to clearly understand and follow their instructions. This audience will only know what is actually written, not what is intended, and that is the way they will be assessed. Again, this step must be approved before students can begin their experiment.
CC Connection: W.8.4 Produce clear and coherent writing in which the development, organization, and style are appropriate to task, purpose, and audience.
Students begin by making a hypothesis that answers their testable question and recording it in their science journal.
Students next conduct their experiment being sure to follow their written procedure. This allows students to recognize if they are missing any steps or if their instructions are unclear at any point and gives them the opportunity to correct their work. I remind students to keep track of their data, including both qualitative and quantitative data.
As students work through their experiment I ask them to document their progress in both video and picture format. At minimum, I have them take pictures of their experimental set up, record videos of their trials, and record a video of them explaining what they are going to be doing but they are free to add material if they wish. Documenting their work in this manner adds a level of interest and creativity for the students while helping to keep them on task. Students will use and reference this material when they prepare a presentation of their findings and experience in the lesson.
The following videos illustrate students capturing their procedure on "tape".
After all data has been collected, students must determine a way to organize it into a neat and understandable data table. I have students to use the examples in their textbook as references while they consider the data they collected. As homework, each student is to create what they feel to be an appropriate data table to display their data. I tell students that there are many ways to do this correctly, but the best data tables include the following:
I use the projector to show students the example data tables and let them know they can access this on our class web page if they need a reference after class and don't have their textbook. I let students know they will compare what they each develop during the next class and will either choose the best or combine elements to create their final data table.