What is the term for the temperature at which water first begins to vaporize into steam at a given pressure?

What is the term for the temperature at which water first begins to vaporize into steam at a given pressure?

• A. Saturation Temperature
• B. Boiling Point
• C. Critical Temperature
• D. Triple Point

Answer: (A)

Saturation temperature is the temperature at which a liquid is in equilibrium with its vapor at a given pressure. At that temperature, the vapor pressure of the liquid equals the surrounding pressure, so the liquid begins to vaporize and form steam; any added heat during this moment goes into converting liquid into vapor rather than raising the temperature further. For pure water at one atmosphere, this condition occurs at 100°C, which is why that pressure’s boiling point matches the saturation temperature. The other terms describe different ideas: the critical temperature is the highest temperature where liquid and vapor can remain separate phases, the triple point is where solid, liquid, and vapor coexist, and while boiling point is commonly used to describe the temperature at which boiling occurs at a given pressure, the thermodynamic term for that equilibrium condition is saturation temperature.

Saturation temperature is the temperature at which a liquid is in equilibrium with its vapor at a given pressure. At that temperature, the vapor pressure of the liquid equals the surrounding pressure, so the liquid begins to vaporize and form steam; any added heat during this moment goes into converting liquid into vapor rather than raising the temperature further. For pure water at one atmosphere, this condition occurs at 100°C, which is why that pressure’s boiling point matches the saturation temperature.

The other terms describe different ideas: the critical temperature is the highest temperature where liquid and vapor can remain separate phases, the triple point is where solid, liquid, and vapor coexist, and while boiling point is commonly used to describe the temperature at which boiling occurs at a given pressure, the thermodynamic term for that equilibrium condition is saturation temperature.