Why don't methane and oxygen react immediately?

Answer 1

For any chemical reaction, there is what is called an activation energy that is required to make that reaction happen. Methane and oxygen both exist as molecules in which there are molecular bonds. In methane, the carbon is bonded to the hydrogen, and in diatomic oxygen, the two oxygen atoms are bonded to each other. So, before the oxygen can bond to the carbon and the hydrogen, all of those existing bonds have to be broken. Once the process begins it is self-sustaining, because it releases a lot of energy, more than enough to break the existing bonds in methane and oxygen. But you still need the activation energy to get things started. This would normally come in the form of a spark. It just takes one small spark to set off an explosion, if you have a mixture of methane and oxygen. Or a pilot light, to light your gas stove.

Answer 2

Methane and oxygen do not react immediately because the reaction requires activation energy to break the bonds within the molecules and initiate the reaction. Additionally, for methane and oxygen to react, they must come into close proximity to each other, which may not always happen instantaneously due to the random motions of molecules in a gas phase.