Final answer:
The primary way water extinguishes fire is by absorbing heat, making it an effective heat sink, as it undergoes an endothermic reaction. In the case of oil fires, water's effectiveness may be limited due to density differences, and alternative methods like fluorinated foam are used instead. Option A is correct.
Step-by-step explanation:
The primary way water extinguishes fire is by absorbing heat. During the process of extinguishing a fire, water undergoes an endothermic reaction, which means it absorbs heat energy. When water is applied to a fire, it absorbs the heat from the fire, which helps in lowering the temperature of the fuel and surrounding environment to below the ignition point, thus helping to put the fire out.
Specifically, when water is heated, it goes through several stages: the water heats up to its boiling point, then it vaporizes into steam, and if further heated, the steam can rise in temperature. Each of these steps requires the absorption of significant amounts of heat energy. This is why water is an effective heat sink, especially in the case of a crude oil fire on a tanker, where incredibly large amounts of energy must be absorbed to combat the fire.
However, the use of water in fighting certain types of fires, such as oil fires, can be complicated due to the fact that oil is less dense than water and therefore does not mix with water. In such cases, other methods like using fluorinated foam, which spreads over the surface to exclude oxygen and trap high energy molecules, are often used. This foam acts as a barrier between the fuel and the oxygen, helping to stop the fire.