Here's why:

* Molecular Structure: Ozone (O3) is a molecule made up of three oxygen atoms. This structure gives it a very specific shape and properties.

* Intermolecular Forces: The forces holding ozone molecules together are relatively weak.

* Boiling Point: Ozone's boiling point is -111.9°C (-171.4°F). This means it only exists as a liquid at temperatures below that.

While ozone is a gas under normal conditions, it can be liquefied or solidified under extreme conditions of pressure and temperature.