Summary

In this activity, students will view an animation that explores density on the particulate level. There are opportunities to make qualitative and quantitative comparisons between substances.

Grade Level

Elementary School, Middle School, High School

NGSS Alignment

This activity will help prepare your students to meet the performance expectations in the following standards:

• Scientific and Engineering Practices:
  • Developing and Using Models

Objectives

By the end of this activity, students should be able to:

• Define density mathematically.
• Determine whether an object will float or sink in a liquid based on their relative densities.

Chemistry Topics

This activity supports students’ understanding of:

• Density

Time

Teacher Preparation: minimal
Lesson: 10-30 minutes

Materials

• Computer and projector with internet access
• https://teachchemistry.org/classroom-resources/density-animation
• Student handout

Safety

• No specific safety precautions need to be observed for this activity.

Teacher Notes

• All of the animations that make up the AACT Animation collection are designed for teachers to incorporate into their classroom lessons. Intentionally, these animations do not have any spoken explanations so that a teacher can speak while the animation is playing and stop the animation as needed to instruct.
• If you assign this to students outside of class time, you can create a Student Pass that will allow students to view the animation (or any other video or ChemMatters article on the AACT website).
• We suggest that a teacher pause this animation at several points or watch it more than once to give students the opportunity to make notes, ask questions, and test their understanding of the concepts presented. The animation is a little over 1 minute long and moves quickly, so students will likely require pausing or multiple viewings to successfully complete the student activity sheet if you choose to use it.
  • In particular, at about 0:55, students are asked to match 4 density values with each of the 4 substances in the animation. Pause the animation here to allow students to make their guesses. (There is a screenshot of this moment included in the student activity sheet for students to record their answers on.)
• In this animation, particulate-level drawings show less dense substances with more space between particles and more dense substances with less space between particles. All particles (regardless of the type of matter) are represented as small, similarly-sized circles. It does not take into account differences in size between the atoms/molecules that make up the various substances. This animation is a very basic introduction to density and the concept that some substances will sink in water and others will float depending on their density relative to water’s.
• For the question at the end of the animation where students are to match densities with the correct substances, they will need to recognize that lower-density materials will float and higher-density materials will sink. (The reference material in this case is water, but other liquids are explored in the extension questions.) At about 1:05, the particle diagrams are all displayed side by side so students can see how densely packed the particles are relative to the other substances.
• Some of the extension questions provide practice with density calculations, which can be removed if you want to keep the activity on a more conceptual level.
• The final extension question is a quick hands-on activity comparing the density of saltwater to freshwater that could be done as an at-home bonus question, an in-class demo, or a short lab. Note that if the egg is too old, it may float in freshwater as well as saltwater (it should only float in saltwater), so be sure the egg is relatively fresh.
• Related classroom resources from the AACT Library that may be used to further teach this topic:
  • Simulation: Density
  • Unit Plan: Chemical Measurement Unit Plan
  • Lab: Density Lab
  • Lab: Graphing Density
  • Lab: Colors of the Rainbow
  • Lab: Bowling Ball – Will it Sink or Float in Water?
  • Demo: Household Densities