Density Detectives
Investigate why some objects float and others sink by exploring the concept of density.
Why do some objects float while others sink — and what does density have to do with it?
Key Vocabulary
Density
The amount of mass in a given volume (Density = Mass ÷ Volume).
Mass
The amount of matter in an object, measured in grams or kilograms.
Volume
The amount of space an object takes up, measured in cm³ or mL.
Buoyancy
The upward force a fluid exerts on an object placed in it.
Displacement
The amount of fluid pushed aside by an object.
Archimedes' Principle
An object floats if it displaces fluid equal to its own weight.
Key Concepts
- 1
Density = Mass ÷ Volume. A small but heavy object is dense; a large but light object is not.
- 2
Water has a density of about 1.0 g/cm³. Objects denser than water sink; less dense objects float.
- 3
Shape can affect whether an object floats — a hollow steel ship floats because its overall density is less than water.
- 4
Buoyancy is the upward force exerted by water that counteracts gravity.