What defines an azeotrope?

An azeotrope is defined as a mixture of two or more substances that has a constant boiling point and composition throughout the boiling process. This means that when this mixture is heated, it vaporizes and condenses at a consistent ratio, behaving as if it were a single substance. In the context of refrigeration, this characteristic allows azeotropes to act like a single refrigerant, making them useful in systems where consistent performance is needed across different operating conditions.

The other options do not accurately describe what an azeotrope is. For example, a blend with variable composition refers to mixtures that can change in their proportions, which is the opposite of an azeotropic behavior. A refrigerant with high ozone depletion potential focuses on environmental impacts rather than the physical properties and behavior of the mixture. Similarly, a refrigerant with a low boiling point does not encapsulate the unique characteristic of having a constant boiling point during phase changes, which is central to the definition of an azeotrope.