If gasoline and air are very flammable why is CO2 not?
If Wood and air are very flammable then why is CO2 and carbon ash not?
The answer to all the above is because the by products of these chemical reactions are very stable substances and are unable to react with other atoms (at least easily).
Water is the result of a chemical reaction between Hydrogen and Oxygen. Oxygen and Hydrogen are both very reactive because the Oxygen Atom and Hydrogen Atom wants to form molecular bonds very strongly.
When these two react they release a lot of energy, this is what creates the heat and light of the flame. But once they have reacted they become incredibly stable.
You need to ADD energy to water to cause it to separate. The textbook example of this is electrolysis where you can apply electricity to water to cause it to separate into Oxygen and Hydrogen.
To simplify: pure hydrogen (or oxygen) have weak molecular bonds between the molecules, leaving them “willing” to easily bond with other molecules rapidly. They release energy in the process, which sustains the fire by providing energy that breaks more bonds.
However, when they bond with each other in H20, those bonds are very strong, so they don’t break easily to start and sustain a fire.
>If pure hydrogen and pure oxygen are both very flammable, why is water not?
Because water is a different substance than Hydrogen and Oxygen.
The characteristics of a compound’s individual components have little to no bearing on most the characteristics of the compound.
Do note that Oxygen is in fact **not** flammable, however pure. It’s an (*the*) oxidizing agent, i.e. its presence allows flammable substances to burn (react with Oxygen).
Since water is the *product* of Hydrogen’s oxidization reaction with Oxygen it can help to think of it as Hydrogen’s “ash”, the inert residue that remains after all the exciting things have already happened.
Hydrogen is flammable, meaning that in the presence of oxygen and given a bit of a push (eg a spark) it burns. Once it’s finished burning, it’s become water. This is, by very definition, the thing that no longer burns after you’ve ignited hydrogen. If water was flammable, then hydrogen burning wouldn’t stop with it but would carry on to hydrogen peroxide (H2O2). The reason why is “chemistry and quantum physics” – to do with how hydrogen and oxygen atoms hang on to electrons individually, in pairs and when combined. Essentially, the total amount of “electron and nucleus sticking together energy” in two molecules of H2O is a lot more than in two of H2 and one of O2, and things aren’t improved by taking one more O2 and ending up with two molecules of H2O2.
Also, oxygen is not flammable. Oxygen, in the presence of itself, stays as it is. Also kind of by definition – if it wasn’t fairly stable, then it wouldn’t just be chilling in our atmosphere.
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