大象传媒

Density

Density describes how closely packed the particles are in a solid, liquid or gas.

All contains particles. The difference between the different states of matter is how the particles are arranged:

  • in a solid 鈥 particles are tightly packed in a regular structure
  • in a liquid 鈥 particles are tightly packed but free to move past each other
  • in a gas 鈥 particles are spread out and move randomly
Solid cube: side length 1 unit, 64 particles in tightly packed lattice. Liquid cube: 1 unit, contains approx 30 particles. Gas cube: side length 10 units contains 15 scattered particles.
Figure caption,
Changing the state of a material will change its density

There is little difference between the density of a liquid and its corresponding solid (eg water and ice). This is because the particles are tightly packed in both states. The same number of particles in a gas would spread further apart compared to in the liquid or solid states. The same mass takes up a bigger volume - this means the gas is less dense.