Question

The point on a phase diagram at which all phases occur simultaneously is called the:

Answer 1

Triple point.

Step-by-step explanation:

Triple point is the point in a phase diagram of a substance where three phases occur simultaneously. It represents the point of a particular temperature and pressure.

For example triple point of water is : 0.01°C (273.16K) and 4.58 mm Hg

In case of four phases of a substance (example sulfur, which has two solid phases and one liquid and one gas) there will be three triple points.

Answer 2

It's called the triple point of the substance, This point is where all phases occur simultaneously.