Question 35 QMED02 - Electrician-Refrigerating Engineer

The Correct Answer is C **Explanation for Option C (Correct):** A definite advantage of water as a fire extinguishing agent is its ability to absorb a massive amount of heat energy (latent heat of vaporization) as it converts into steam (vapor). When water vaporizes, it expands rapidly, increasing its volume by approximately 1,700 times. This rapid expansion and volume increase displaces oxygen surrounding the fire. By cooling the fuel below its ignition temperature (the primary action) and simultaneously smothering the fire by reducing the oxygen concentration (the secondary action), water effectively extinguishes the flame. **Explanation of Incorrect Options:** * **A) alternate expansion and contraction as water in liquid state becomes vapor:** While water expands upon vaporization, the key action is the sustained rapid expansion and cooling, not an alternating cycle of expansion and contraction. This description is inaccurate regarding the primary mechanism of fire suppression. * **B) absorb smoke and gases as water is converted from liquid to vapor:** Water vapor can interact with smoke and gases (washing them out of the atmosphere), but this is a secondary effect. The definite advantage in fire extinguishment is the heat absorption and volume expansion, not the scrubbing of combustion products. * **D) rapidly contract as water is converted from a liquid to a vapor:** This statement is factually incorrect. When water turns into vapor (steam), it **expands** dramatically (by about 1,700 times its original volume), it does not contract.