Lesson Summary In lesson 2 and 3, students had a variety of experiences with magnets.  Now, in this lesson, they will learn about “fair tests” and, in teams, conduct an experiment to find out how strong different combinations of magnets are.  Then the results of the experiment will be graphed.  A similar experiment using electromagnets will be designed by students in Lesson 9 and performed in Lesson 10. Teacher Background Magnets are used in many ways.  The magnet that holds a door closed must be strong, but not too strong.  How strong do magnets need to be?  How strong is too strong?  Someone had to do some experiments to find the answers to these questions.  A “fair test” is another way of doing a “controlled experiment.”  A “fair test” is an experiment that keeps all things the same, except the thing that you are trying to investigate. The experiment that the students perform in this lesson explores how the strength of a magnet changes when it is combined with other magnets.  The variables that need to be controlled in this experiment are the kind of magnets used, the thickness of the tongue depressor, and the weight of the washers. Students will think about whether two magnets are stronger than one magnet.  Do the magnetic strengths of two magnets combine?  You will be asking the students how the test can be made fair.  Give them the following example of an unfair test:  Two students wanted to know which of them had a stronger arm.  They decided to arm wrestle, but the first student used the whole hand and the second students used only the little finger.  Was this a “fair test”?  How could you make it fair? Set-up/Management Tips Copy Activity Sheet 2 for each student and prepare materials for distribution. Discuss different ways/terminology to arrange magnets such are side by side, horizontally, vertically, etc.  Discuss how to set up a data table. Literacy Support The following words are key vocabulary words that will be introduced in this lesson and reinforced throughout the unit: No new vocabulary introduced this lesson.