eli5 since diamonds are compressed carbon is it combustible? I don’t think so but why?
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Everything is flammable, but some things, like diamonds, are only flammable when you get them very very very hot.
Everything is flammable, but some things, like diamonds, are only flammable when you get them very very very hot.
Combustion is an oxidation reaction: breaking apart the atomic bonds that exist and replacing them with atom:oxygen.
The difficulty in burning diamond is that all of the carbon is very, very strongly bonded to other carbon. This is the same reason that carbon is very hard, it is difficult to physically break off a piece of diamond because all of the carbon is strongly bonded to other carbon in the crystal. In an analogous manner it is difficult to break off a single carbon in order to react it with oxygen.
However, it is difficult to burn diamond, not impossible. By raising the temperature you can add a ton of energy into the atoms that is stored as vibrations of atoms in the crystal lattice and makes the bonds relatively easier to break. At ~850C the diamond will start reacting with oxygen in the air and combust.
In practical terms that means diamonds feel non-combustible (most flames are much less hot than this, so I would eg. expect diamonds to survive a house fire.). But they can combust under the right circumstances.
Combustion is an oxidation reaction: breaking apart the atomic bonds that exist and replacing them with atom:oxygen.
The difficulty in burning diamond is that all of the carbon is very, very strongly bonded to other carbon. This is the same reason that carbon is very hard, it is difficult to physically break off a piece of diamond because all of the carbon is strongly bonded to other carbon in the crystal. In an analogous manner it is difficult to break off a single carbon in order to react it with oxygen.
However, it is difficult to burn diamond, not impossible. By raising the temperature you can add a ton of energy into the atoms that is stored as vibrations of atoms in the crystal lattice and makes the bonds relatively easier to break. At ~850C the diamond will start reacting with oxygen in the air and combust.
In practical terms that means diamonds feel non-combustible (most flames are much less hot than this, so I would eg. expect diamonds to survive a house fire.). But they can combust under the right circumstances.
Diamonds are not chemically stable at the surface of the earth in the presence of oxygen, and SHOULD react (burn; combine with oxygen to make carbon dioxide). Your question is a good one.
The bonds among the carbons in diamond are very strong, so it takes a lot of energy to break them. Once broken, the reaction of the released carbon with nearby oxygen will happen very fast. You can drive the reaction (cause diamond to burn) if you provide enough heat (enough energy to cause carbon in the diamond to break its bonds), but that much heat is pretty rare up here at the surface of the earth, so it doesn’t happen except when humans make it happen on purpose.
The basic problem is that the energy gained when a carbon combines with oxygen is not enough to make a carbon in the diamond break apart from the matrix, so even if you do manage to get a reaction started, it will not continue. The reaction stops because it does not release enough energy to keep itself going. The fire puts itself out, in a way, sort of like how trying to burn wet wood also tends to fail. Energy needed to keep the reaction going is lost in trying to heat up the fuel, unless the fuel (the diamond) is already really hot.
So, while diamond “should” react with air and make carbon dioxide, it simply doesn’t. It is what is called “metastable”, which means it is not the most stable form for the condition, but it can’t get from what it is now to that other form where it would be “happier”. It would, if it could. A big energy hill has to be crossed though, and there isn’t nearly enough energy to climb that hill at normal earth surface temperatures.
Diamonds are not chemically stable at the surface of the earth in the presence of oxygen, and SHOULD react (burn; combine with oxygen to make carbon dioxide). Your question is a good one.
The bonds among the carbons in diamond are very strong, so it takes a lot of energy to break them. Once broken, the reaction of the released carbon with nearby oxygen will happen very fast. You can drive the reaction (cause diamond to burn) if you provide enough heat (enough energy to cause carbon in the diamond to break its bonds), but that much heat is pretty rare up here at the surface of the earth, so it doesn’t happen except when humans make it happen on purpose.
The basic problem is that the energy gained when a carbon combines with oxygen is not enough to make a carbon in the diamond break apart from the matrix, so even if you do manage to get a reaction started, it will not continue. The reaction stops because it does not release enough energy to keep itself going. The fire puts itself out, in a way, sort of like how trying to burn wet wood also tends to fail. Energy needed to keep the reaction going is lost in trying to heat up the fuel, unless the fuel (the diamond) is already really hot.
So, while diamond “should” react with air and make carbon dioxide, it simply doesn’t. It is what is called “metastable”, which means it is not the most stable form for the condition, but it can’t get from what it is now to that other form where it would be “happier”. It would, if it could. A big energy hill has to be crossed though, and there isn’t nearly enough energy to climb that hill at normal earth surface temperatures.
I actually remember a video from Earth Sciece class where Julia Child actually cooked a diamond down to ash in a kiln to demonstrate that all carbon burns.
I actually remember a video from Earth Sciece class where Julia Child actually cooked a diamond down to ash in a kiln to demonstrate that all carbon burns.
They burn into co2! They absolutely burn you are correct. No real explanation needed even, other than you need high heat and a lot of oxygen to be provided. They will 100 percent turn into nothing but gas.
They burn into co2! They absolutely burn you are correct. No real explanation needed even, other than you need high heat and a lot of oxygen to be provided. They will 100 percent turn into nothing but gas.
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