Apologia Physics: Module 1, Motion, and Density

Module 1 has a discussion of math, units, factor-label, significant figures, and derived units, specifically density.  Our Co-op class meets twice a week for 1 1/4 hours each class.  Today, we resumed working with the Pasco Motion Sensor, Exploring Motion Graphs (a free Sparkvue download from Pasco), the Airlink2, and an iPad, which has the Sparkvue app downloaded.  (Remember, eBay often has the Airlink2 and sensors for much less.)  (Here is a free link for this lab: Pasco MatchGraph software.)We finished this lab and started on the density labs, beginning with Will a Bowling Ball float?  The way I conduct this activity is to ask questions: Will a bowling ball float?  What determines if an object floats in water?  What do we mean by density?  What is the density of water?  What calculations are necessary to determine whether or not a bowling ball will float?  I provide the circumference formula and the formula for the volume of a sphere here.   I brought a ten pound bowling ball, a bathroom scale, metric rulers, and some string to measure the circumference of the bowling ball in order to derive the radius, which you need to calculate the volume of the bowling ball.  If you have a bigger group, you can use bowling balls which are 10 lbs, 12 lbs, or 16 lbs.  Spoiler alert.  The 10 lb ball will float; a 12 lb ball will bobble in ice water because it is about 1.0 g/mL.  A 16 lb ball will sink.  The second density lab requires 5 piece metal density set, plastic graduated cylinders, water, a digital scale, and rulers.  My scale took a hit during the move.  Fortunately, the metal cubes are all 20 g.  I used this lab, Arbor Scientific Density Blocks Activity, for the densities, and asked the guys to determine which method is more accurate, similar to Flinn's Measurement Challenge.  Basically, which means of measuring volume is more accurate, volume by displacement or volume by direct measurement?  The only hitch was the kids confused mm and cm. So, we'll resume and complete this density lab next Tuesday.  Once they determined the respective densities of the metal cubes, I showed them how to calculate the percent error.  We'll start by determining which method is more accurate next time.  I should mention that we're in the local library's Maker Lab.  Awesome, right?