What type of fire can be put out safely with water?

Question

Wood or grease?

Answer 1

Wood.  

Water should not be used on a grease fire.  Grease is less dense than water and therefore will float (or water sinks in grease).  In a grease fire, water sinks in hot (hotter than 212F) grease.  The water then heats to 212 and boils, expanding ~1,000x in volume.  This will send the burning grease everywhere, spreading fire and most likely burning you.  

Answer 2

Wood, grease floats on water, so if u try to put it out with water, then it will just spread the grease resulting in u spreading the fire.

whereas wood will just be extinguished and wont be spread

Answer 3

Wood, or most paper or plastic fires. The reason it is unwise to throw water onto burning grease is the grease is far above the boiling point of water. The water won't mix either, and the droplets of water explode as steam. This splatters droplets of scalding, burning grease over a wide area. With burning gasoline, the temperature is lower, but the gasoline just floats on top of the pool of water and splashing just spreads burning gasoline around. Electrical fires are also unwise to try and extinguish with water. The water can cause a massive short circuit and any sparks involved can also spread the fire. Non-wood fires are best extinguished with sand or something which generates CO2, like a canister extinguisher. Burning grease in a container can be extinguished by removing any heat source and covering the container. This will not work with gasoline fires however. The gas might reach its flash point and this will blow the lid off the container.