Density Curriculum

Section 4—Lesson 15: What Happens in Sinking or Floating When the Relationship Between Densities Changes?

Understanding Goals

Subject Matter

• Sinking and floating is the result of the relation between the density of the object and the density of the liquid. The substance with the greater density will sink in a substance with lesser density.
• Changes to the liquids or objects can result in changes in the system and in the outcome of sinking or floating.

Causality

• People often use linear models to explain whether something sinks or floats. This makes it hard to see what is really going on.
• A relational causal model helps us attend to the density differential that accounts for sinking and floating.
• If we manipulate the density of a substance, it will not change its relationship to another substance until it reaches the point where the differential between the densities changes direction. This threshold or "tipping point" can create sudden effects even if the causes have been accumulating over time.