Here's why:

* Unique to a substance: Each pure substance has a specific and consistent freezing/melting point. This means that if you have a pure sample of water, it will always freeze at 0°C (32°F) and melt at the same temperature. This property helps distinguish one substance from another.

* Intensive property: The freezing/melting point doesn't depend on the amount of the substance. Whether you have a drop of water or a gallon of water, it will still freeze at 0°C.

* Useful for identification: Scientists and engineers use freezing and melting points as key indicators for identifying and verifying the purity of substances.

Therefore, freezing and melting points are characteristic properties because they are unique, intensive, and helpful for identification.