Hands-on Activity: Determining Densities
Educational Standards :
Pre-Req Knowledge (Return to Contents)
Learning Objectives (Return to Contents)
After this activity, student should be able to:
Materials List (Return to Contents)
Introduction/Motivation (Return to Contents)
(The associated lesson Introduction, in which students determine the density of a rectangular box filled with an unknown substance, provides adequate introduction to the activity as well. To further motivate students, add the following specific introductory information.)
Today I have a great variety of different objects for you to determine their densities. Some of the materials have what scientists call "known densities." In other words, their densities have been calculated to a high degree of accuracy in a lab, using sophisticated measuring devices.
After you have determined the densities of the objects, you can compare your results to the known densities. So, your challenge is to measure and weigh your objects very carefully, so your results are very close to the known densities.
Vocabulary/Definitions (Return to Contents)
Procedure (Return to Contents)
Part 1: Regular Shapes
Part 2: Irregular Shapes
Present the class with the second assortment of objects, whose shapes are not regular.
Part 3: Density of Water and Graphing of Results
Troubleshooting Tips (Return to Contents)
If students are not rounding their measurements correctly, or if they are "over-rounding" their measurements, their results may vary widely from those of their classmates and/or the known values for some of the materials. Watch students as they make their measurements to make sure they are rounding lengths to the nearest 0.5 or 1 millimeter, masses to the nearest 0.05 or 0.1 g, and water volumes to the best accuracy available for the graduated cylinders being used. Also, some students tend to always round measurements up. For example, for an actual measurement of 25.72 grams, such a student will round to 25.8 grams, rather than the correct rounding of 25.7 grams.
Investigating Questions (Return to Contents)
Assessment (Return to Contents)
Activity Extensions (Return to Contents)
Provide students with ice cubes (as large and rectangular as possible) and ask them to determine the density of ice. See the associated lesson's Extension Activities section for further information and discussion ideas.
Provide each student group with a can of Coca-Cola and a can of Diet Coca-Cola. Ask them to determine the density of each. They may be surprised to find that the diet drink is less dense than the regular drink. An alternate way to demonstrate this is by simply placing each can in an aquarium of water: the diet cola floats while the regular cola sinks. Ask students to read the list of ingredients on each can and try to determine what is responsible for the density difference. Most likely it is due to the density differences in the sweeteners used, with the synthetic sweetener aspartame being less dense than the natural sugars used in non-diet soft drinks.
ContributorsMary R. Hebrank, project writer and consultant, Duke University
Copyright© 2013 by Regents of the University of Colorado; original © 2004 Duke University
Supporting Program (Return to Contents)Engineering K-PhD Program, Pratt School of Engineering, Duke University
Acknowledgements (Return to Contents)
This lesson and its associated activity was originally published, in slightly modified form, by Duke University's Center for Inquiry Based Learning (CIBL). Visit http://www.biology.duke.edu/cibl for information about other CIBL resources for K-12 science and math teachers.