Do Bowling Balls Sink or Float in Water

"What are we doing to help kids achieve?"

This year I wanted to start off the course with a lab that would grab my student's attention! I walked in with five bowling balls and an Argument Driven Inquiry template. Before I go any further, I know this is a popular question used by other science teachers and I cannot take credit for thinking it up. I do want to give credit where credit is due...I am just not sure who used it first. I heard about this idea from someone else and I did not believe bowling balls would ever float. So I decided to do some experiments to test out the claim. (It may have come from Pam Scott of Michigan. She wrote an activity called "Get into the Game with Team Density" while she was working with the Grand Valley State University Target Inquiry program. There was also a J.Chem. Ed. article entitled Bowling for Density, written by Kathleen Holley and Diana Mason, Kirk Hunter.¹ 

Students broke up into teams with the question, "Do bowling balls sink or float in water?".  They actually developed the question as a class. The teams decided they would need to find the "density" of their bowling ball. Most were a bit fuzzy on the concept of density. I was able to introduce it using the (Ck12) book we use. Almost all groups measured the mass and volume in pounds and inches cubed. I was O.K. with that. Technically, it is still density. They solved for the densities of all the bowling balls. Most classes were able to accurately predict which balls would float and which would sink correctly four out of five bowling balls. This prediction led to great discussions about how to measure. One girl said that she could calculate and predict which would float but really did not know the "why" of floating. We stopped and examined the concept of buoyancy. One student wanted to know what would happen if we drilled more holes in the bowling balls. Wouldn't it sink then? If not, why not?

Overall, this was a good but challenging way to start the year. The students experienced some success with the scientific method. This led to rich discussions about measuring, data, predictions and answering the question "why" when trying to build concepts. This was also an informal way to do formative assessment with students. How well do they work as teams?  How do they observe and record data?  Can they manipulate data?  Where are they with their math abilities? I would say this is worth giving a try. Also, you can almost always find a couple of local bowling alleys to supply some old bowling balls.

Do you have a lab to grab students attention at the start of the year? Please consider sharing....

¹Kathleen Holley and Diana Mason, Kirk Hunter, Bowling for Density,  J. Chem. Educ., 2004, 81 (9), p 1312A.