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. 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. A homogeneous system will often have more than one component (like salt and water), but the mixture will be uniform throughout the sample.

For a heterogeneous system there may be clumping of salt in the salt water, or parts of the water that are saltier than others. Figures 1 and 2 below show how heterogeneous and homogeneous systems differ.

• Heterogeneous and Homogeneous Gas Particles
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  Figure 1. A heterogeneous mixture of molecules in a gas. Note that: the density (and pressure) is different throughout.
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  Figure 2. A homogeneous mixture of molecules in a gas. Here, the density (and pressure) is uniform throughout.

These terms are also important for catalysis. For information on homogeneous vs. heterogeneous catalysis please visit the Chem Guide.

For Further Reading

• Pressure
• Density
• Phase change
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