Dissolving Gobstoppers Using Controls and Variables


Nancy Landau-Gahres

Sunset Park Learning Center, Brooklyn


Summer Research Program for Science Teachers

August 2007


Grade Level:  

Middle School




²       Provide a simple laboratory experience that practices the proper use of controls and variables.

²       Record results in charts and graphs, appropriately labeled.

²       Complete a correctly formatted lab report.



Teaching Point Students will conduct a controlled experiment in their laboratory groups.



Stage and Duration of Activity:  3 class periods (not including time to teach background concepts)





Hand-outs and Resources: See attached Lab Report Rubric and Lab Data Sheet. (PDF)



Expected Background Information:

Students should be familiar with controls and variables.  They should also understand basic graphing concepts and have experience recording data in a well-designed chart.  Students should also be familiar with the concept of iterative data, meaning that the tests are repeatable.   


Assessing Prior Knowledge:

This is a great opening activity to check students’ understanding of investigable questions.  This activity would most appropriately be done at the beginning of the class period day 2.  It will allow students to recall the nature of investigable questions and begin generating appropriate questions for this project.

²       Students will receive 5 index cards with questions on them.  The questions will be both investigable and non-investigable.  Students will categorize these in their groups.

²       Groups will share out one investigable question and one non-investigable question from their set.  These will be recorded on the computer and projected on the screen.  The class will discuss the nature of these questions and argue the reason for their categorization.  (Why is this question investigable?  How could you test question?)

Day 1

²       Students will conduct initial tests with gobstoppers.  Each student in the group will have a role (timer, recorder, observers, stirrer).

²       The group will establish conditions for testing, ie. how many stirs per minute, temperature of the water, when to identify color change.

²       Students will conduct the test two times and record all data carefully


Day 2:

²       Teacher will assign each group to change one variable only.  This will help students understand what it means to manipulate only one variable at a time. 

²       Students will conduct tests two times and record data.

²       Group members will decide what variable they would like to change for the following day and request materials using a materials request form (see attached)


Day 3: 

²       The group will conduct tests two times, recording data. 

²       If time allows groups can manipulate another variable.


Follow Up/Data Analysis:

All students will be required to complete a lab report (see attached Lab Report Rubric).  This report will be complete with graphs, tables and detailed explanation/analysis of results.




National Science Standards:


Standards A & C