Hot Water or Cold Water: Which Extinguishes Fire Faster?
The answer is- Hot water.
Hot water extinguishes fire faster as compared to cold water.
Explanation: How fire Occurs?
Fire is actually an event rather than a thing. Typically, fire occurs from a chemical reaction in presence and right combination of its three elements: heat, fuel, and an oxidizing agent (usually oxygen). To eliminate fire we have to stop the supply of any one of the element.
Explanation: How water extinguishes the fire?
However, cutting the supply of fuel doesn’t right away extinguishes fire, but definitely it restricts its further dispersal. Without a steady supply of oxygen, a fire starts to simmer down and ultimately dies. The third element, heat can be worked upon by putting some heat absorbing material that can reduce the available heat which is required to continue the chain reaction. Now the question arise-
Why water is added to extinguish fire?
Water extinguishes fire by cutting two of the elements which are must for the fire to prevail—heat and the oxidizing agent. Putting water on fire, cools down the fire by absorbing heat (energy) to transform from liquid to gas. Additionally, as soon as liquid water is converted into vapor, it establishes a barrier among the burning gas and atmospheric oxygen.
So from here it is clear that water changes from liquid to gas to halt fire from spreading.
Hot Water or Cold Water: Which Extinguishes Fire Faster and why?
To convert water into vapours we need to heat it. The process by which a substance moves from the liquid state to the gaseous state is called boiling. If we will add cold water, it will take little more time to extinguish fire as it will need to warm up and than achieve the boiling point to transform into vapours.
Transformation of water produces into vapours a cooling effect just like evaporating sweat present on our skin gives cooling effect.
In hot water, molecules already have some heat so they quickly gets evaporated and gives the cooling effect. Once the boiling point of water (100°c) is achieved, the heat being absorbed is no longer utilized to raise the temperature, but rather to break the bonds between the water molecules. The amount of heat required to break all the bonds and thus convert liquid water to water vapor is called the latent heat of vaporization. For water, the latent heat of vaporization is quite high, standing at about 2,260 kJ/kg.
Final Words :
When cold water is used, time is first spent in bringing the cold water up to the boiling point. Since the temperature of hot water is already near its boiling point, less time is required to reach 100°c. Thus, the high latent heat of vaporization of water comes into play sooner for hot water than it does for cold water, so heat is absorbed at a faster rate by hot water. Also, a quicker conversion to steam means a faster establishment of a barrier between the burning fuel and oxygen.