Density is a physical property of matter that describes how much mass is contained in a given volume. It tells us how tightly particles are packed in a substance.
Definition
Density = the mass per unit volume of a substance.
Formula
Density (ρ)=Mass (m)/Volume (V)
- ρ = density
- m = mass of the substance
- V = volume occupied
SI Unit
- Mass → kilogram (kg)
- Volume → cubic meter (m³)
- Density unit = kg/m³
(Other common units: g/cm³, g/mL for smaller quantities).
Examples
- Water has a density of about 1 g/cm³ (1000 kg/m³).
- Iron is denser (about 7.9 g/cm³), which is why it sinks in water.
- Wood is less dense than water, so it floats.
👉 In short: Density = Mass ÷ Volume, and it explains whether substances sink or float.
Would you like me to also give a real-life example problem showing how to calculate density?