Question

Hydrogen and oxygen both are combustible but their compound water is not.Why?

Answer 1

Firstly, in a chemical reaction, it's not necessary that the properties of the reactant and the product will be same. That's the beauty of chemistry. Water is stabilized by special bonds {Vander Waals bonds}
Secondly, water is a liquid and hydrogen and oxygen are gases. So, that gives water extra stability.
Thirdly, combustion is basically the reaction of a substance with oxygen and water itself is oxygenated so no such affinity to combustion.