Particles and states of matter

Everything is made of tiny particles. In a solid they are packed in a pattern and vibrate; in a liquid they are close but move past each other; in a gas they are far apart and move quickly in all directions. Density tells you how much mass is packed into each cm³.

Key facts

  • Solid: fixed shape, particles vibrate in place.
  • Liquid: flows, takes the shape of its container.
  • Gas: spreads out to fill any space.
  • Density = mass ÷ volume (g/cm³ or kg/m³).

Worked examples

Example 1

A block has a mass of 240 g and a volume of 30 cm³. What is its density?

  1. Divide. 240 ÷ 30 = 8
  2. So 8 g/cm³

Answer: 8 g/cm³

Example 2

Ice floats on water. What does that tell you about their densities?

  1. Things float when they are less dense than the liquid.
  2. So ice is less dense than liquid water (its particles are slightly more spread out).

Answer: Ice is less dense than water