Homogeneous vs heterogeneous

In most technical applications homogeneous means that the properties of a system are the uniform throughout the entire system; heterogeneous (also inhomogeneous) means that the properties change within the system.[1] Any system with two phases like ice and water are said to be heterogeneous.

For example, homogeneous systems have the same composition, density and pressure throughout. While a homogeneous system will often has more than one component (like salt and water), the mixture will be uniform throughout the sample. For a heterogeneous system there's clumping of salt in the salt water, or parts of the water that are saltier than others. The figures 1 and 2 below show heterogeneous and homogeneous systems.

These terms are also important for catalysis, for information on homogeneous vs. heterogeneous catalysis please see here.


  1. A Dictionary of Chemistry (7 ed) by Richard Rennie, published 2016.
  2. 2.0 2.1 Image made by a member of the energy education team by using the PhET resource found here: https://phet.colorado.edu/en/simulation/gas-properties, Accessed July 14th, 2017.