Here's why:

* Physical properties are characteristics of a substance that can be observed or measured without changing the substance's chemical composition.

* Boiling is a physical change where a liquid transitions into a gas. It doesn't change the chemical makeup of the helium.

Therefore, the boiling point of liquid helium (which is extremely low, around -269°C or 4.2K) is a characteristic that describes its behavior under certain conditions and is considered a physical property.