CO = 28g/mol
CO2 = 44g/mol
O2 = 32g/mol
H2O = 18g/mol
Air = 29g/mol
Air is composed of roughly 78% nitrogen and 22% oxygen (close enough for averaging the molecular weight, anyway)
An incomplete combustion will take fuel and oxygen and burn them producing CO, CO2, and H2O as follows:
Hydrocarbon(wax) + O2 -> CO + CO2 + H2O +wax
Not all the wax will be burned in all likelihood (see \"how to relight a group of candles\" by the same guy), so I threw it in there for completion's sake. Of all the products of the combustion, CO2 is the most important in this case, and the amount of CO2 produced will far surpass the amount of CO produced at the temperatures we're talking about.
Given that, if it were left up to weight alone, the bottom candle would go out first because the product gas CO2 would be heavier than the ambient air and would fall to the bottom, snuffing the lower candle. However, it isn't just the weight that matters: it's the density.
In this case, the denisty of the product gases will be far less than that of the ambient air (due to the temperature difference), and therefore they will rise to the top of the jar. Their rising to the top in the center will push the air down the outer sides of the jar, and the net result is that the top candle will be snuffed before the bottom candle is.
Doesn't anyone notice how the smoke from a lit candle doesn't fall? At the same temperature CO2 might be denser then Oxygen but since the CO2 is heated more then the Oxygen it probably becomes less dense and rises in the container, pushing the Oxygen down and snuffing out the top candle first.
Reply to #14:
And I just confirmed it by trying it out myself. Top candle went out first 5/5 times when I put a candle stick and a votive in a upended blender and vase. I used a water seal to keep it air tight, so I'm content that I'm right.
This is super super simple. The reaction is O2 + Hydrocarbon(wax) -> CO2 + H2O. Air weighs 29g/mol, O2 is 32g/mol, H2O is 18g/mol and CO2 is 44g/mol. Since CO2 is the heaviest gas it will settle at the bottom and put out the lower candle first. A cool trick you can do is fill a cup with some baking soda and pour in vinegar and cover it while it bubbles. Light a candle, and then pour the CO2 that is produced over the candle to put it out. This is also the reason why CO2 is used by fire extinguishers, because it creates a layer on the ground.
I imagine that it depends on the size of the jar more than anything else. If the jar is sufficiently small, then the convection currents caused by the heat of the flames will override the typical densities of the gases. Since the carbon dioxide is heated from the combustion of the candle, it will momentarily be far less dense than the air in the jar and will rise to the top of the jar. Since this is happening on both candles, the top candle will go out first because it will be supplied with carbon dioxide from the lower candle's convection current, not to mention giving off it's own current in the first place. The rising carbon dioxide will \"push\" the cooler air down around the sides of the jar, creating a looping effect current (gases moving up the jar in the center of the cylinder and down the sides). Because of this circulation, the air will be fed to the lower candle and the top candle will become snuffed with carbon dioxide.
However, if the jar were sufficiently large, then there would be time for the temperatures to equalize between the air and the carbon dioxide, so then the carbon dioxide's higher weight would be a factor, and I imagine that the lower candle would go out first. This is pure supposition, but it stands to reason based on the densities of the materials.
Based on the size of the jar in this experiment, I would imagine that it's not big enough to let the temperature gradients/convection currents work themselves out, and therefore the top candle will go out first.
candles burn oxygen and produce carbon dioxide. carbon dioxide is heavier than oxygen, so will sink to the bottom, forcing the remaining oxygen to the top. this will cause the bottom candle to go out first.
oxygen (outside air) will seep in from the bottom because the seal is not perfect, thus the candle on top will go out first.... oh yeah, and the remaining oxygen in the canister will be at the bottom keeping the lower candle fuled
both candles will go out at the same time, because because oxygen will to expand within the space so both candles will have same amount oxygen to burn.
CO2 weighs more than air, so as the process goes the air tends to remain at the top (because is ligher than CO2)...sooo....the smaller candle goes off first!
taller candle goes off first because, as burning goes, air-oxigen tends to go to the bottom of the jar because it weights more than what goes out of the combustion...
You are suppose to crawl in a burning building. So I'm thinking the oxygen molecules must drop for some reason (though the crawling could be related to avoiding chemical fumes).
Er, I'd like to have two candles here but it's not the case. What I think is going to happen is that the shorter candle is going out in first place. The hot air tends to go up so the longer candle will be out of oxygen later than the shorter one.
Nice experiment/question though, I like to play around these sort of things.
Reply to #17: Here are the weights of everything involved:
CO = 28g/mol
CO2 = 44g/mol
O2 = 32g/mol
H2O = 18g/mol
Air = 29g/mol
Air is composed of roughly 78% nitrogen and 22% oxygen (close enough for averaging the molecular weight, anyway)
An incomplete combustion will take fuel and oxygen and burn them producing CO, CO2, and H2O as follows:
Hydrocarbon(wax) + O2 -> CO + CO2 + H2O +wax
Not all the wax will be burned in all likelihood (see \"how to relight a group of candles\" by the same guy), so I threw it in there for completion's sake. Of all the products of the combustion, CO2 is the most important in this case, and the amount of CO2 produced will far surpass the amount of CO produced at the temperatures we're talking about.
Given that, if it were left up to weight alone, the bottom candle would go out first because the product gas CO2 would be heavier than the ambient air and would fall to the bottom, snuffing the lower candle. However, it isn't just the weight that matters: it's the density.
In this case, the denisty of the product gases will be far less than that of the ambient air (due to the temperature difference), and therefore they will rise to the top of the jar. Their rising to the top in the center will push the air down the outer sides of the jar, and the net result is that the top candle will be snuffed before the bottom candle is.
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Reply to #17: As #13 said, CO2 is heavier than Oxygen, and it makes sense.
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ok this isnt that difficult, the Taller candle goes out first. WHY??? simple O2 is heavier. Carbon monoxide is lighter than oxygen.
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Doesn't anyone notice how the smoke from a lit candle doesn't fall? At the same temperature CO2 might be denser then Oxygen but since the CO2 is heated more then the Oxygen it probably becomes less dense and rises in the container, pushing the Oxygen down and snuffing out the top candle first.
Atleast thats what I think it is.
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Reply to #14: And I just confirmed it by trying it out myself. Top candle went out first 5/5 times when I put a candle stick and a votive in a upended blender and vase. I used a water seal to keep it air tight, so I'm content that I'm right.
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Reply to #13: Unless of course what 12 said, the hot CO2 snuffs out the top candle.
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This is super super simple. The reaction is O2 + Hydrocarbon(wax) -> CO2 + H2O. Air weighs 29g/mol, O2 is 32g/mol, H2O is 18g/mol and CO2 is 44g/mol. Since CO2 is the heaviest gas it will settle at the bottom and put out the lower candle first. A cool trick you can do is fill a cup with some baking soda and pour in vinegar and cover it while it bubbles. Light a candle, and then pour the CO2 that is produced over the candle to put it out. This is also the reason why CO2 is used by fire extinguishers, because it creates a layer on the ground.
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I imagine that it depends on the size of the jar more than anything else. If the jar is sufficiently small, then the convection currents caused by the heat of the flames will override the typical densities of the gases. Since the carbon dioxide is heated from the combustion of the candle, it will momentarily be far less dense than the air in the jar and will rise to the top of the jar. Since this is happening on both candles, the top candle will go out first because it will be supplied with carbon dioxide from the lower candle's convection current, not to mention giving off it's own current in the first place. The rising carbon dioxide will \"push\" the cooler air down around the sides of the jar, creating a looping effect current (gases moving up the jar in the center of the cylinder and down the sides). Because of this circulation, the air will be fed to the lower candle and the top candle will become snuffed with carbon dioxide.
However, if the jar were sufficiently large, then there would be time for the temperatures to equalize between the air and the carbon dioxide, so then the carbon dioxide's higher weight would be a factor, and I imagine that the lower candle would go out first. This is pure supposition, but it stands to reason based on the densities of the materials.
Based on the size of the jar in this experiment, I would imagine that it's not big enough to let the temperature gradients/convection currents work themselves out, and therefore the top candle will go out first.
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this is the answer:
candles burn oxygen and produce carbon dioxide. carbon dioxide is heavier than oxygen, so will sink to the bottom, forcing the remaining oxygen to the top. this will cause the bottom candle to go out first.
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oxygen (outside air) will seep in from the bottom because the seal is not perfect, thus the candle on top will go out first.... oh yeah, and the remaining oxygen in the canister will be at the bottom keeping the lower candle fuled
is he endorsing that we play with fire?
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Both candles will go out at the same time because both of them need and use the same amount of oxygen
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both candles will go out at the same time, because because oxygen will to expand within the space so both candles will have same amount oxygen to burn.
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CO2 weighs more than air, so as the process goes the air tends to remain at the top (because is ligher than CO2)...sooo....the smaller candle goes off first!
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taller candle goes off first because, as burning goes, air-oxigen tends to go to the bottom of the jar because it weights more than what goes out of the combustion...
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When do we see the answer?
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You are suppose to crawl in a burning building. So I'm thinking the oxygen molecules must drop for some reason (though the crawling could be related to avoiding chemical fumes).
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Both will go out at the same time because both of them use the same amount of oxygen.
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Er, I'd like to have two candles here but it's not the case. What I think is going to happen is that the shorter candle is going out in first place. The hot air tends to go up so the longer candle will be out of oxygen later than the shorter one.
Nice experiment/question though, I like to play around these sort of things.
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I think the candle at the top will go out first, I am not sure why but that is my guess.
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