The bubble point is the temperature that the first refrigerant in a blend turns into vapor.

The bubble point is the temperature that the first refrigerant in a blend turns into vapor.

• A. The temperature that the first refrigerant in a blend turns into vapor
• B. The temperature at which the last refrigerant in a blend turns into vapor
• C. The temperature at which the liquid begins to boil
• D. The temperature at which the mixture becomes completely vapor

Answer: (A)

Bubble point is the temperature at which a liquid mixture first begins to form vapor at a given pressure. In a refrigerant blend, the component with the lowest boiling point vaporizes first, so the first bubbles appear when that component starts to boil. That onset—the point where vapor just starts to appear from the liquid—defines the bubble point. As for the other choices, the moment when the last component boils would be the end of boiling, not the start; simply saying the liquid begins to boil is close but doesn’t emphasize that it’s the first vapor from the most volatile component; and the mixture becoming completely vapor would be the final point, not the initial onset.

Bubble point is the temperature at which a liquid mixture first begins to form vapor at a given pressure. In a refrigerant blend, the component with the lowest boiling point vaporizes first, so the first bubbles appear when that component starts to boil. That onset—the point where vapor just starts to appear from the liquid—defines the bubble point. As for the other choices, the moment when the last component boils would be the end of boiling, not the start; simply saying the liquid begins to boil is close but doesn’t emphasize that it’s the first vapor from the most volatile component; and the mixture becoming completely vapor would be the final point, not the initial onset.