Do all substances have three different states of matter? For example, can a limestone rock exist as a solid, liquid, and gas at different temperatures? Does it, theoretically, have a triple point diagram?

1 Answer
May 21, 2016

You can draw phase diagrams for most substances, but the materials in each phase aren’t necessarily the same substance.


For example, the phase diagram of limestone (calcium carbonate) is shown below.

At 1 bar, calcium carbonate decomposes to CaO and CO2 at 898 °C.

As pressure increases, the temperature required for the decomposition increases until, at above 80 bar, the decomposition stops altogether.

Instead, we have an equilibrium mixture of solid and liquid calcium carbonate.