How is water a product of combustion?

Answer 1

Combustion is a sequence of exothermic(heat releasing) chemical reactions between a fuel, most likely a hydrocarbon, and an oxidant, which will always be oxygen.

Water, more specifically water vapor, is formed in a combustion reaction because the reactants (initial compounds/elements) chemically change when energy is added to the equation to form the products of water vapor and often carbon dioxide.

For example:

2H2 + O2 → 2H2O(g) + heat

In the above combustion reaction, hydrogen and oxygen reaction with each other to form water vapor, and in the process release heat. The above reaction is an example of the process used to propel rockets.

Or:

CH4 + 2O2 → CO2 + 2H2O + heat

Again, in this reaction both reacting compounds have the necessary elements to form water vapor as a product. This is the case in every combustion reaction.

Answer 2

The main combustion of water is oxygen.....true dat! ;)