What Is Density?
Density is a fundamental physical property defined as mass per unit volume: ρ = m/V. It describes how tightly packed the matter in a substance is. Density is intrinsic — it does not change based on the amount of material. A gold bar and a gold ring have the same density (19.32 g/cm³), even though they have different masses and volumes.
Common Material Densities
| Material | Density (g/cm³) | Floats in Water? |
|---|---|---|
| Water (4°C) | 1 g/cm³ | ✓ Yes |
| Wood (Oak) | 0.75 g/cm³ | ✓ Yes |
| Wood (Pine) | 0.5 g/cm³ | ✓ Yes |
| Ice | 0.917 g/cm³ | ✓ Yes |
| Gasoline | 0.75 g/cm³ | ✓ Yes |
| Air (at STP) | 0.001225 g/cm³ | ✓ Yes |
Applications of Density
- Buoyancy: Objects with density less than the fluid float; greater density sinks
- Material identification: Density helps identify unknown substances
- Quality control: Manufacturing uses density to check material purity and consistency
- Meteorology: Air density affects weather patterns and flight performance