Interactive, scaffolded model
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Part A: The students observe several plastic soda bottles filled with various substances and discuss the varying density of those substances. After being given the numerical density of each substance, the students observe while some are placed in an aquarium tank filled with water. After the first observations, students are asked to predict whether the next couple of bottles will sink or float.
Part B: Students use the computer to measure the density of various combinations of atoms with varying mass and varying space between the atoms.
Students will be able to:
This activity is one of a larger module: Atoms in Motion (http://www.concord.org/~barbara/workbench_web/unit1/index.html)
Density is the ratio of mass to volume, how much mass in each unit of volume.
Additional Related Concepts
The key factor in why a hot air balloon floats has to do with the density of the air inside as compared to the density of air outside the balloon. Less dense substances float in more dense substances. The bigger the difference in density and the larger the volume of the low density substance, the greater the buoyant (upward) forces will be. Heating the air causes the molecules to spread further apart, lowering the density of the gas inside the balloon.
Other macro connections: