Variables and Hypothesis

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SWBAT identify the variables and hypothesis for their individual science fair experiments.

Big Idea

This lesson provides students with a review of identifying variables and creating a hypothesis prior to identifying the variables and hypothesis for their own experiments.


5 minutes

As students enter the room, they are given a note card and are asked to write down the scientific question they will investigate for the science fair.  The students then post their note cards on a bulletin board.  This serves as a way to ensure that the students have developed a question to explore rather than just selected a demonstration to conduct.  The note cards will also be referred to at various times throughout the duration of the science fair process.  This development of the scientific questions addresses Science and Engineering Practice (SP)1 Asking Questions and Defining Problems.


15 minutes

I ask the students to take out their notes from the problem solving unit (What is Science - Flipped), so they can refer back to them as we review controls and variables.  As a class, we discuss variables.  I begin by asking the students to list variables in different real world contexts.  For instance, I ask them to describe the variables that impact the taste of soda, plant growth, or the attendance at an outdoor sporting event.  Prior to sharing their thoughts with the class, I have the students write down at least three different variables for each scenario.  As the students write, I circulate through the room to view their answers and to answer any questions they have about the process.  I then ask the students to share their thoughts with the other students in their group.  After providing students with a chance to discuss, I call on each group and have them provide at least one variable that has not already been shared by another group.

Once the students demonstrate an understanding of the term variable, I have them focus the definition more on science experiments and we examine independent and dependent variables.  I do this by reading the scientific questions they wrote earlier in the lesson.  I read a question to the class and ask the students to develop an independent variable and a corresponding dependent variable.

From there we move to a discussion regarding controlled elements in an experiment.  I remind the students that they need to try and control as many aspects of the experiment as possible; ideally controlling everything but the independent and dependent variables.  We review various experiment ideas and the controls necessary to ensure the success of the experiment.  Our review of the various elements of an experiment helps to address SP3 Planning and Carrying Out Investigations.

After we have reviewed controls and variables, I review the process for developing a hypothesis.  I remind the students to use If...then... statements.  I write this format on the board: If the (independent variable) increases/decreases/type of change, then the (dependent variable) will increase/decrease/type of change.  I then have the students practice writing hypotheses for various scientific questions as listed on our bulletin board.

Science Buddies also has a variables and hypothesis worksheet that can be used as a part of the science fair process.


15 minutes

I then hand out the identifying controls and variables worksheet.  I have the students first work on the page by themselves and once they have completed it, they may discuss their answers with their science fair partners.  Once the students have consulted their partners and combined their information, they trade papers with another partner set.  This partner set, then, reviews their information and is required to write a paragraph response about the information that has been written.  Once the papers have been returned to the original owners, they are required to read through the information and address any issues before turning the paper in to be assessed. 

As the students work on this process, I circulate through the room to ensure that students understand the task.  I also check their hypotheses to make sure they are following the proper format.  Beyond that, I observe the students as they review the work of their peers to check that they are critically analyzing the information rather than just noting areas of agreement.

This examining variables video provides an example of a student examining the work of other students. This interaction has guidelines and expectations, which I discuss in my reflection.

Wrap up

5 minutes

At the end of class I lead a whole group discussion asking the students to remind me of the definitions of controls and variables.  I also ask them to explain why we have controls in experiments.  I then go around the room to ask students to share the question they are exploring and their hypothesis.  As students share their hypothesis, I ask the class to explain whether they agree or disagree and to explain why.  By doing this, the students are able to share their ideas and experiences with the rest of the class.