General Question

AstroChuck's avatar

Oxygen is very flammable. Hydrogen is even more so. So why doesn't water burn?

Asked by AstroChuck (36647 points ) December 29th, 2009

As you can tell, chemistry is not my strongpoint. But it seems to me that if the components of water are flammable then water itself should be as well. Obviously this isn’t the case. Why not?

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45 Answers

AstroChuck's avatar

But neither hydrogen nor oxygen have carbon in them

I’m so confused.

MrItty's avatar

Hydrogen and Oxygen are also both gasses. Yet water isn’t (at least, not below 100°C).

Two elements combining to form a different compound do not at all transfer their properties to the new compound.

gggritso's avatar

When elements combine their properties are not necessarily preserved. Bonding of atoms creates a profound change. Even though the atoms themselves don’t change, when they interact you start dealing with a different thing altogether.

MrItty's avatar

Sodium and Chlorine are both rather bad for Human Beings to ingest. Yet stick them together and you get Sodium Chloride – NaCl – table salt.

MrItty's avatar

@gemiwing that commenter’s “in simple terms” are simply wrong. Carbon is not required for burning.

Yetanotheruser's avatar

Because H2O already contains oxygen. Burning is an oxidation process.

RedPowerLady's avatar

Because it is wet. (just a guess)

tinyfaery's avatar

Because nothing is simply the sum of it’s parts. Not even in science.

gasman's avatar

One of the basic principles of chemistry is that compounds don’t generally share the properties of their constituent elements. The chemical bonds that unite an oxygen atom with two hydrogen atoms (to form a water molecule) confer vastly different properties, as suggested by your question.

That’s why there’s such a profound difference between a mixture and a compound.

MrItty's avatar

@RedPowerLady if by “wet” you mean “liquid”, then so is Alcohol. If by “wet” you mean “made of water”.... well that’s rather a tautalogy. :-)

LostInParadise's avatar

@Yetanotheruser got it right. In a sense water results from hydrogen burning. In coming together, the hydrogen and oxygen electrons released energy, moving to a lower energy state, and are happy campers.

RedPowerLady's avatar

@MrItty Haha. I was trying to think of something else wet that would be flamable, alcohol purely slipped my mind. Got me.

El_Cadejo's avatar

@RedPowerLady what about gasoline :P

Yetanotheruser's avatar

Alcohol and gasoline, and most other flammable liquids, are hydrocarbons. The energy of the flame edit or the spark end edit oxidizes the hydrogen (creating water vapor) and the carbon (leaving you with CO2. That is why the CO2 is such a big part of the “carbon footprint”.

antimatter's avatar

My guess is that it has something to do with the atoms. When these two gases are joined
they become stable.

Lightlyseared's avatar

oxygen is not flammable.

NaturalMineralWater's avatar

Because if it weren’t for this simple fact than I wouldn’t be able to cook anything for dinner.

Haleth's avatar

Once they have been combined they don’t burn. But as pure gases they are very, very flammable. One of my favorite demonstrations in science class was combining hydrogen and oxygen. The teacher brought a balloon full of hydrogen and a balloon full of oxygen to the front of the classroom and popped them both. There was a huge noise and a big puff of flame, and then a puddle of water on the floor. If I remember right, it’s because they are both very reactive, especially with each other (?) Once they have formed water, there is a very strong chemical bond, and no need for further reaction.

Lightlyseared's avatar

@AstroChuck Oxygen on its own does not burn. It helps other things burn.

phoenyx's avatar

Because you can’t create energy out of nothing. By adding a spark to start the reaction, combining Hydrogen and Oxygen creates water and releases energy (exothermic reaction). So, it requires energy to split the water back into it’s component Oxygen and Hydrogen atoms. If you could burn water, you could have infinite energy.

jlm11f's avatar

I see @Lightlyseared has already said what I wanted to. O2 is not flammable. The gas itself does not burn, it allows for other things to burn it it’s presence.

stranger_in_a_strange_land's avatar

Oxygen is not flammable, it is an oxidizer, part of the combution process. Hydrgen is very flammable in thr presence of oxygen. Water is the product of the reaction between oxygen and hydrogen, has stable chemical bonds and reacts only as a solvent, not a combustible material.

RedPowerLady's avatar

@uberbatman okay okay, i’m a dumbass, haha

AstroChuck's avatar

Oxygen must be flammable in a pressurized liquid state, right? You always see notices that tell you no smoking or open flame in a house where oxygen is in use.

Zaku's avatar

Water does burn. Just add sodium.

RedPowerLady's avatar

@AstroChuck That must be correct. My grandfather was on oxygen. Lit up a cig and the whole thing blew up in his face. Wasn’t pretty. Luckily he was fine.

phoenyx's avatar

@Zaku
That’s a different reaction. It is sodium reacting with water to produce hydrogen. The hydrogen is reacting with excess oxygen in the air (and producing water). You aren’t burning water.

2 Na + 2 H2O → 2 NaOH + H2

nebule's avatar

@NaturalMineralWater I loved that…that made me laugh!!! really really lots!!! xx

@tinyfaery Because nothing is simply the sum of it’s parts. Not even in science – can I put this in my quote book!! it’s brilliant! x

FireMadeFlesh's avatar

Combustion is an oxidation reaction. That releases energy. When methane burns, we get the reaction

CH4 + 2O2—> CO2 + 2H2O + energy

Hydrogen peroxide is an oxidised form of water, but its bonds require more energy than those of water, so the oxidation reaction for water consumes energy rather than releasing it. Therefore, it will not burn.

tinyfaery's avatar

@lynneblundell It’s all yours.

Jayy's avatar

Same reason you can’t breath underwater.

Brian1946's avatar

Burning is usually the process of a substance combining with oxygen.

Because water is hydrogen that’s already in compound with oxygen, it won’t burn.

AstroChuck's avatar

@Jayy- Billions of creatures breathe underwater.

Yetanotheruser's avatar

@AstroChuck Those billions of creatures are equipped with gills, or some other device to extract dissolved O2 from the water. It has nothing to do with the H2O molecule.

We actually have a kind of combustion, or oxidation, happening in our bodies when we turn carbohydrates (sugars) into energy, water and CO2. It goes like this:

C6H12O6 (sugar, or carbs) + 6 O2 (6 molecules of Oxygen)= 6 CO2 (6 carbon dioxide)
+ 6 H2O (water) + Energy

The opposite reaction is called photosynthesis, and it’s how green plants convert CO2 and sunlight to carbohydrates and oxygen:

6 CO2 + 6 H2O + Energy (usually in the form of sunlight) = C6H12O6 + 6 O2

LostInParadise's avatar

@Yetanotheruser , The respiration reaction you mention invovles the formation of water from hydrogen and oxygen and the initial part of photosynthesis involves the decomposition of water into hydrogen and oxygen.

nebule's avatar

@tinyfaery thank you xxx

engineeristerminatorisWOLV's avatar

Oxygen supports burning and hydrogen is flammable,but when they chemically combine,they loose the properties they initially have as individual elements.The reson is change in bond structure and orbital configuration of electrons in atoms after the electron sharing.It is not possible for hydrogen to liberate energy when present in water than being an individual element.It’s just like a kid being notorious away from parents and when with them,he has to hold on the side effects of his itchy butt.

AstroChuck's avatar

You said butt. Hehe.

Yetanotheruser's avatar

@LostInParadise Yeah! That’s what I meant!~

Shuttle128's avatar

It has much to do with the energy states of the hydrogen and oxygen. The product of burning hydrogen and oxygen is water! Water is the lower state of energy for both chemicals so energy is required to liberate them from their bonds. You can burn the oxygen and hydrogen after using electrolysis to split the water molecules but it takes more energy to split the bonds than you get from burning the gases.

Ltryptophan's avatar

Have you ever heard of a hot water balloon going up in flames a la hindenberg?

kailash's avatar

Hi this question was posed to us recently.

How come oxygen on its own and hydrogen on its own are either flamable and or increase the size of a fire yet, when those same 2 x components or gases are formed together in union to make water, they as water! Puts the fire out!?

Also we know as per science, no oxygen no fire.

But the answer still needs to be found for the thoughts below

So how’s that possible. What is missing in water? Or what is present in water that both individual gases are missing or have that make them individual, that evidently makes water capable of dowsing flames and put fires out yet the gases either add to the fires in there own ways. Go figure?

FireMadeFlesh's avatar

@kailash Oxygen and hydrogen in their gaseous form are bonded relatively weakly. The covalent bonds in water are much stronger, meaning it requires much more energy to dissociate. Water absorbs the heat energy from a fire without dissociating, so the heat does not induce a chemical reaction.

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