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How come hydrogen.?

How come hydrogen.? Topic: Not one less reaction paper
June 26, 2019 / By Dalilah
Question: how come hydrogen is a explosive gas and oxigen can start fires but them put together makes water that helps put out fire????
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Best Answers: How come hydrogen.?

Blanid Blanid | 3 days ago
Your question is actually a bit more complicated than the other answers have given it credit for. The other posters are correct to the extent that they describe the difference between dihydrogen (H2) or dioxygen (O2) and water (H2O). The whole point of distinguishing between elements and compounds is that different substances are *different* -- that the physical and chemical properties of water are not just the additive sum of those of hydrogen and oxygen. H2 is explosive precisely because when exposed to O2 it forms an unstable mixture that can undergo a highly exothermic reaction to form H2O, a very different and very stable compound. O2 can start fires precisely because it can form more thermodynamically stable compounds with nearly every other element on the periodic table, again by undergoing often violently exothermic reactions (called, as you said, "fires"). So O2 and H2 react with each other violently, and thereby form a more stable (and so far less reactive) material, namely water. Which is why water won't burn any more, it's already *been* burnt. It's already the most stable compound that can be formed from hydrogen and oxygen, so throwing it on a fire doesn't cause any further reaction. OK, so that's why water itself doesn't burn. But nobody has addressed the second part of your question -- why water will actually extinguish a fire, and stop something *else* from burning. Although O2 can react with organic material (e.g. paper wood coal gasoline methane propane and anything else you might feel like setting on fire today) in an exothermic reaction to form more stable products (ie CO2 and water), it doesn't usually do that without help. Paper doesn't explode upon contact with air. A balloon filled with methane and oxygen just sits there. Until you light a match and start the reaction going: the fire requires some heat to start. Fortunately, the fire also releases heat, so it's self-activating once it gets going, which means that once a fire begins, it'll keep burning until you run out of fuel -- *unless* you can remove that heat and take it away. Water can absorb a huge amount of heat, especially if it boils off. This isn't a chemical change, it's just liquid phase H2O turning into gas phase H2O. Throw water on a fire -- water absorbs heat, heat water boils, hot gas phase water steams off and removes the heat, burning fuel cools down, there's no longer enough heat to initiate the reaction with O2, the fire goes out. However, the CO2 in a fire extinguisher is better. Not only does it not burn (same reason as for water), and not only does it absorb heat, removing the activating energy for the reaction, it also smothers the flames by creating a cushion of dense gas around the fire, effectively preventing O2 from getting to the fuel. It denies the chemical reaction one of the reactants, so the reaction simply stops.
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Blanid Originally Answered: How come hydrogen.?
Your question is actually a bit more complicated than the other answers have given it credit for. The other posters are correct to the extent that they describe the difference between dihydrogen (H2) or dioxygen (O2) and water (H2O). The whole point of distinguishing between elements and compounds is that different substances are *different* -- that the physical and chemical properties of water are not just the additive sum of those of hydrogen and oxygen. H2 is explosive precisely because when exposed to O2 it forms an unstable mixture that can undergo a highly exothermic reaction to form H2O, a very different and very stable compound. O2 can start fires precisely because it can form more thermodynamically stable compounds with nearly every other element on the periodic table, again by undergoing often violently exothermic reactions (called, as you said, "fires"). So O2 and H2 react with each other violently, and thereby form a more stable (and so far less reactive) material, namely water. Which is why water won't burn any more, it's already *been* burnt. It's already the most stable compound that can be formed from hydrogen and oxygen, so throwing it on a fire doesn't cause any further reaction. OK, so that's why water itself doesn't burn. But nobody has addressed the second part of your question -- why water will actually extinguish a fire, and stop something *else* from burning. Although O2 can react with organic material (e.g. paper wood coal gasoline methane propane and anything else you might feel like setting on fire today) in an exothermic reaction to form more stable products (ie CO2 and water), it doesn't usually do that without help. Paper doesn't explode upon contact with air. A balloon filled with methane and oxygen just sits there. Until you light a match and start the reaction going: the fire requires some heat to start. Fortunately, the fire also releases heat, so it's self-activating once it gets going, which means that once a fire begins, it'll keep burning until you run out of fuel -- *unless* you can remove that heat and take it away. Water can absorb a huge amount of heat, especially if it boils off. This isn't a chemical change, it's just liquid phase H2O turning into gas phase H2O. Throw water on a fire -- water absorbs heat, heat water boils, hot gas phase water steams off and removes the heat, burning fuel cools down, there's no longer enough heat to initiate the reaction with O2, the fire goes out. However, the CO2 in a fire extinguisher is better. Not only does it not burn (same reason as for water), and not only does it absorb heat, removing the activating energy for the reaction, it also smothers the flames by creating a cushion of dense gas around the fire, effectively preventing O2 from getting to the fuel. It denies the chemical reaction one of the reactants, so the reaction simply stops.

Airla Airla
They react strongly together and give a stable product. This product is very stable due to hydrogen bounds particularly strong in water. One characteristic of water is its very high specific heat and this serves to extinguish fire . You need comparatively to other products a very high energy to rise the temperature of water for a given value. So ,if you throw water on a fire a great quantity of the energy serve to rise the temperature of water and to evacuate heat.
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Topher Topher
Hydrogen reacts with oxygen because they are a thermodynamically unstable mixture. Water on the other hand extinguishes fire because it blocks air (consequently oxygen) away from the combustion area.No air no fire. I don't think this has to do with water being a product of combustion .
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Reagan Reagan
Another way of looking at combustion is oxidation. For example, we burn CH4 = we oxidise C, as the end product is CO2. That is why everything on earth need oxygen to burn. By burning hydrogen, we are effectively oxidising it to give H2O. (oxidation state of H increases from 0 to +1) As H2O is the fully oxidised form of hydrogen, it is very stable and can be used to put out fire. *If you notice, CO2 which is the fully oxidised form of carbon, is also used to put out fire. Similarly, SiO2 can also be used to put out fire.
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Matthew Matthew
When two individual atoms have different chemical properties combine, this compound has different properties as well. Compounds do not follow genetics.
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Matthew Originally Answered: DrAnders said. no more hydrogen being produced?
It's essentially correct that no more hydrogen is produced. There might be tiny amounts produced when high-energy collisions cause a nucleus to fission, but the primary trend is for lighter nuclei to be fused into heavier nuclei in the cores of stars. But there's still plenty of hydrogen. The interstellar medium, from which stars are formed, has a composition mostly determined by the primordial outcome of the Big Bang (75% hydrogen, 25% helium by mass), with some heavier elements that were produced in stars and released by supernova explosions. Star formation in the interstellar medium tends to occur when the gas is compressed by a shock wave -- either a density wave in a spiral galaxy, or the shock from a large explosion such as a supernova. I don't think the universe will run out of hydrogen, but other things will happen that decrease star formation over time: 1) Most stars do not become supernovae. Lower-mass stars become white dwarfs, and their mass is normally locked up forever. Over time, mass is transferred from the interstellar medium to stars. 2) As the interstellar medium loses mass, it will become less dense, and therefore star formation will become increasingly rare. Lower star formation will produce fewer supernovae, which means fewer shock waves, which means even less star formation. Over the long term, the abundance of hydrogen in the universe will decrease. I suspect it won't decrease very much, but I don't know what the "final" abundance is predicted to be. -- edit There's an interesting paper on this subject called "The Galactic Millennium", by Paul Hodge of the University of Washington: http://www.journals.uchicago.edu/doi/pdf... A galactic year is the time it takes the sun to revolve around the center of the galaxy -- roughly 225 million years. Hodge talks about what the universe will be like when it is 1000 galactic years old (i.e., 225 billion years old, as compared to the current age of 14 billion). To make numbers simpler, Hodge talks about the universe 100 billion years from now rather than 225 billion. Here is part of Hodge's paper: "Throughout the early parts of the Galactic millennium new stars were born, many of which were formed from gas and dust that was recycled from evolved previous generations. But this process cannot go on forever, as white dwarfs, neutron stars, and black holes are sinks that trap material in forms that cannot be recovered. Eventually the Galaxy will be as devoid of material for forming stars as the elliptical galaxies appear to be now. ... Perhaps, however, as the gas density decreases further, the rate will decrease or maybe even stop abruptly when the gas density drops everywhere below a critical density. ... In A.D. 100 billion star formation probably will have ceased, and there will be no Orion Nebula to light up the Galactic arms (and, anyway, the arms themselves may have faded into the feeble background disk)." Hodge's paper is fairly short and non-technical, so you might want to take a look at his predictions for the distant future. -- edit I'll add something in response to Richard R's answer. I didn't mention the expansion of the universe here because I don't think it's relevant. The usual statement by cosmologists is that expansion affects the universe as a whole but doesn't affect things on the scale of individual galaxies. To the extent that this is true, the expansion of the universe can be ignored when you're talking about star formation in galaxies. Perhaps the expansion will eventually affect the galaxies (such as in the "big rip" model), but star formation will probably come to an end long before then for the reasons mentioned earlier. -- edit DrAnders, in contradiction with Paul Hodge's article, doesn't think that white dwarfs and neutron stars are a typical "end state" of matter. This is a debatable point. It's true that white dwarfs will become type Ia supernovae if they obtain enough additional matter to exceed the Chandrasekhar limit (about 1.4 solar masses), but this nearly always happens because of accretion of mass from a close binary companion. Except for the close-binary-companion case, however, white dwarfs will remain white dwarfs forever unless they have a chance collision with another object. Such collisions are incredibly rare, and will not happen unless two objects are headed almost exactly towards each other. Therefore, I suspect that Hodge is correct, and that much matter will be locked up in the three end states he mentions -- white dwarfs, neutron stars, and black holes. On the other hand, you might argue that even if collisions are very rare, they will happen if you consider events over an incredibly long time scale. On yet another hand, however, over such enormous time scales, perhaps the universal expansion will affect galactic dynamics and therefore reduce the chance of collisions. Finally, if the "big rip" model is correct, the end state is entirely different. In short, we're getting into the realm of considerable speculation and uncertainty. Also, note that Hodge mentions that he expects other astronomers to have some disagreements about his view of the distant future. Nobody has a definitive answer to this question. For your original question, however, things are simpler. Hydrogen and helium were created in the big bang. Today, we have a bit less hydrogen than there was then, because some of it has fused into heavier elements in stellar cores and supernova explosions. No new hydrogen is being created, but neither have we lost much since the big bang. (This tells you something about the enormous energy in nuclear fusion. Despite the huge amounts of energy released by stars over the last 14 billion years, the loss of hydrogen has been very small. Our oil crisis on earth is playing out over the scale of a couple of centuries, but 14 billion years of stellar energy have barely made a dent in the hydrogen supply.) -- edit DrAnders -- I don't necessarily disagree with you, I just don't know. You're right that there are drag forces that work against white dwarfs in the very long run. But it's also possible that whatever makes the universe expand and even accelerate will eventually affect the internal structure of galaxies. Both of these would take a very long time to have much effect. There's plenty of time in eternity, but the question is which effect is faster. Given our lack of understanding of most of the universe (in the forms of dark matter and dark energy), we're in a poor position to predict the distant future. Hodge's article might be a pretty good description of 100 billion years from now, because that's only an eight-fold extrapolation from the present time. We know that lots of double stars have survived for billions of years, so 100 billion years is not too much of a stretch. At some point (a trillion years? a quadrillion years?) we lack the knowledge to extrapolate. We learned about the acceleration of the expansion only 10 years ago, and I'm sure there will be other surprises in store. (By the way, it wasn't me who gave your answer a thumbs-down. Whoever did that was unjustified.) -- edit I thought I was done with this answer, but I just read an article in the current Scientific American (March 2008) called "The End of Cosmology", and the authors make predictions about the universe in the far future (and their prediction contradicts my own guess for the future abundance of hydrogen). Here is some information from the article: a few minutes after the big bang: 76% hydrogen 24% helium present day: 70% hydrogen 28% helium 2% heavier elements 1 trillion years in the future: 20% hydrogen 60% helium 20% heavier elements 100 trillion years in the future: last star burns out So there's your long-range forecast for the next 100,000,000,000,000 years -- a time long enough to astonish even astronomers. There's something they don't mention: Whatever matter is locked up in neutron stars or black holes can't be associated with atomic elements, but their article doesn't indicate the fraction of such matter. It does, however, say that eventually (beyond 100 trillion years), the galaxy will collapse into a black hole; so in this, the authors' view of the future is similar to that of DrAnders. The uncertainty in such predictions can be shown by mentioning the "big rip" hypothesis, which predicts that the entire universe will be torn apart in about 50 billion years. That's a very different scenario for the future universe, and gets back to the overall theme of my answer: We just don't know. I'm very confident that the earth and universe will survive 2012, but am much less certain about 50 billion years out.

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