Is it a chemical reaction to convert liquid oxygen to gaseous oxygen?

A chemical reaction is understood as the transformation of one or more initial substances into substances that differ from them in chemical composition or structure.

When liquid oxygen is converted into gaseous oxygen, there is no change in the chemical structure of the substance. In both cases, the oxygen molecule has the formula O2 (and the structural formula O = O).

In the given example, a change in the state of aggregation occurs, and this process refers to physical phenomena, and not to chemical ones.

As an example of a chemical change in oxygen, we can consider the formation of ozone, which has the formula O3. The reaction occurs when oxygen molecules are irradiated with ultraviolet light or in electrical discharges. In this case, part of the oxygen molecules “breaks down” into atoms and ozone molecules are formed.

3O2 = 2O3

In this example, there is a change in the chemical structure of a substance, therefore this process is a chemical reaction.