## Those Vexing Variables

### Terrie LyonsSanta Rosa District Schools

#### Description

Students learn to recognize the dependent and independent variables in an experiment by practicing manipulation of variables. They also practice designing experiments that contain the two types of variables.

#### Objectives

The student knows how to identify the independent and dependent variables in an experiment.

#### Materials

- Variable worksheets and answer keys. (See attached file).
- Enough yarn or twine cut in 18-inch lengths to have for students to work in groups of 3's. You will need one piece per group.
- One large paper clip for each group.
- One penny for each group.
- Stopwatch for each group or class clock with a minute hand.
- Extra lengths of yarn or twine.
- Several rulers or yardsticks.
- Scissors for cutting yarn.
- Grading rubric (See attached file).

#### Preparations

2. Cut 18- lengths of yarn or twine, enough for students to work in groups of 3.
3. Have a penny and a large paper clip for each group.
4. Have extra yarn on hand along with rulers and yardsticks to measure it with, and scissors to cut it.
5. You may wish to provide extra coins or some other type of weight for students to use in the hands on phase.
6. Provide some means of timing the activity, either with stopwatches or with a clock with a second hand.

#### Procedures

1. Grab the students' attention by demonstrating the pendulum experiment. See attachment for directions.

2. Ask the students to identify ways that the experiment could be changed which would change the outcome. Allow time for discussion. For possible answers see attachment.

3. Explain to the students that the parts of the experiment that can be changed are the variables. At this time give the students the definitions of an independent, dependent, and control variables.

4. Provide each student with a copy of the Variable Identification worksheet. Explain to them that they are to read the descriptions of the experiments on the sheet, and identify the variables in each one.

5. Upon completion of the sheet, go over the answers to the variable identifications. Answer any questions or clear up any misconceptions that the students may have. For answer key, see attachment.

6. Now explain to the students that they will have the opportunity to work with the pendulum experiment and practice manipulating the variables. Provide them with the directions for the experiment. See Pendulum Activity attachment. Have extra yarn or twine available so they can increase the length of the pendulum.

7. As the students work, circulate through the room questioning them about which variable is the independent one and which is the dependent one.

8. After they have had the opportunity to try several variations of the experiment, provide them with the Variable Check-Up sheet. See attachment. Explain to the students that their responses on this sheet will be used for evaluation purposes.

9. Wind up the lesson by collecting all materials and the evaluation worksheet. Review the importance of limiting the number of variables in an experiment.

#### Assessments

As a formative assessment, students can be observed participating in the class discussion of variables and in the pendulum activity. A summative grade can be given each student based on the student's responses to the follow-up activity, Variable Check-Up. A grading rubric is provided in the associted file.

#### Extensions

This lesson can be modified to include the importance of using a control in an experiment by including it on the grading rubric and by having the students identify the controls on the worksheet experiments.