Lesson 7 of 7

Density

Goal: Calculate density and explain it with particles.

Puzzles for this lesson

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A beaker of water. A cork floats on top and a steel bolt lies at the bottom

Density tells you how much mass is packed into each cubic centimetre of a substance.

density = mass ÷ volume

  • The units: mass in grams (g), volume in cubic centimetres (cm³), density in g/cm³.
  • A solid is usually much denser than a gas. Its particles are packed close together, so far more of them fit into the same space.
  • Water has a density of 1 g/cm³. Cork is less dense than water, so it floats. Steel is denser, so it sinks.
SolidGasmany particleshigh densityfew particleslow density

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Key words in this lesson

Particle A tiny piece of matter, far too small to see

Solid Has a fixed shape and a fixed volume

Gas Spreads out to fill its container, and can be squashed

Density The mass of one cubic centimetre of a substance

For teachers: AQA 3.5.1 · Cambridge 9Cp.02, 9Cp.03