Summary

In this lab, students will carry out measurements and calculations to determine whether a bowling ball will sink or float in water.

Grade Level

Middle School, High school

NGSS Alignment

This activity will help prepare your students to meet the following science and engineering practices:

• Scientific and Engineering Practices:
  • Using Mathematics and Computational Thinking
  • Planning and Carrying Out Investigations

Objectives

By the end of this lesson, students should be able to

• Understand the concept of density related to sinking and floating.

Chemistry Topics

This lesson supports students’ understanding of

• Density
• Dimensional analysis

Time

Teacher Preparation: 15 minutes

Lesson: 30 minutes

Materials

• Ruler
• String
• Balance
• Bowling ball
• Other measuring tools students may request

Safety

No specific safety precautions are needed for this experiment.

Teacher Notes

• Students initially guess that the bowling ball will sink in water. After all the lab groups make measurements and can predict the outcome of the test, I drop a ball into a big plastic storage container full of water. The look on their faces when the 8-lb ball floats is priceless, and it’s a great hook for learning to do math in the first two weeks of school. I also do this as a demo for the parents at Open House and they love it too. It's a good activity and memorable.
• Students should know before doing this activity an object will sink in water if it is more dense than water (1.0 g/mL) and it will float if it is less dense.

• Be sure to use a bowling ball less than 12 lbs.A 12 lb bowling ball has just about the same density as water, and anything heavier will sink.You can find used bowling balls relatively inexpensively on eBay, or perhaps by contacting a bowling alley or looking at yard sales.
• For added impact, you could use 3 different bowling balls – one that is less than 12 lbs and floats easily, one that is 12 lbs and is barely floating, and one that is heavier than 12 lbs and sinks.This demonstrates the fact that density is a ratio – the volume doesn’t change much between the three, but the mass does, and it alters the density and thus the sinking/floating behavior.
  • If you don’t have a big tub of water, or run out of time, or just want a quick way of getting the same point across, check out this quick 3-minute video demonstrating this exact concept.
• Students may need reminding that 1 mL = 1 cm³, so they should be measuring in cm so that when they do calculations, the units will match up to the provided density of water (1.0 g/mL) and give them something they can compare meaningfully without converting it to other units.
• A bowling ball will probably have too much mass for a typical school balance to be able to measure – they often max out around 2000 g.If your balances don’t measure high enough to get the mass of a bowling ball, you could provide students with the conversion between pounds and grams (453.6 g = 1 lb) and tell them the weight of the ball (8 lbs) and have them convert it to grams.