Now that you have collected and thought about your data, discuss again what properties of an object you think determine whether it will sink or float.


Sinking or floating has something to do with both mass and volume. If something is heavy for its size, it will sink. If it is light for its size, it will float. We can measure heaviness by mass and size by volume. To help predict whether an object will sink or float, scientists compare an object's mass to its volume. To compare, they find the ratio of the object's mass to its volume. This ratio is called density.

For example, if a rock has a mass of M = 65 g and a volume of V = 23 cc, its density is

Sinking and floating have something to do with density. We will explore this more by finding the density of some objects and looking for patterns in the data.

  1. Complete data tables like the ones below on the Sink and Float Data Tables page in the Student Activity Book. Write the density of each object as a ratio of its mass to volume.