system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does pouring water on a grease fire make it worse?
gpt
Oil burns at much, *much* higher temperatures than water boils.  And oil floats on top of water.

So when you throw water onto a grease fire, the water sinks below the oil and is flash-boiled to steam by the intense heat, which blows the oil out like a small explosion.  This causes the oil to break into thousands of tiny droplets.  All those droplets have a *lot* more surface area than the original pool of oil, allowing the oil to mix with oxygen at a greatly-increased rate, which speeds up the combustion of the oil so much that it transitions from "on fire" to "exploding" (this is the same general reason why a pile of sawdust is perfectly safe, and you could put a cigarette out in it, but a large cloud of sawdust in the air is an explosion hazard).

So the end result of throwing water on oil is a giant fireball of flaming oil droplets that will probably set your house on fire.

**Edit:** Clarified some wording.