Why is it that hydrogen explodes, and oxygen causes fire...that?

Question

H2O causes fire to go out?

Answer 1

Because molecules have very different properties from their individual atoms. Salt is sodium chloride. Sodium explodes in water. Chlorine is a poisonous green gas. The two together are tasty.

Answer 2

Hydrogen explodes when in the present of a flame/spark and oxygen gas. It will not explode if there is no oxygen present.

Oxygen is required to cause a fire as teh fire needs oxygen to be able to burn, otherwise it goes out on its own (ie: fireblanket, CO2 fire extinguisher)

H2O (water) contains hydrogen and oxygen, but is not like gaseous hydrogen or gaseous oxygen. It's boiling point is ~200 degrees higher, is liquid at room temperature, and has a very stable bond. Water also cools down a fire when it is poured on. The lower temperature causes the burning to be slower. Also as water does not burn, water-soaked materials need to evaporate the water out of them before they can burn again (put a water-soaked log on a campfire, it will take a long time before all the steam evaporates out of it before it will actually catch). By putting water onto a fire, it removes one of the three parts of the fire triangle (heat, oxygen, fuel). By removing the fuel, the fire must go out. Removing the oxygen also works (ie: oil well fires put out with explosives), and I suppose putting a house fire into a ~3 kelvin degree room would also probably put out the fire too, but that is impractical.