What's in the air

[TeslaFan]

So I'm trying to visualize mainly what's in the atmosphere and just the ease of aerosolization of seemingly anything and I'm at the basic level right now. So I've read about the composition of air which most people have heard - 78% N, 21% O, and 1% other gases. And also Asimov on Chemistry pg. 93 that there are about 27 quintillion molecules in 1 cc of gas at STP is helping with a mental image. I guess I'm mainly wondering about the aersolization of particulate matter - is every molecule capable of being aerosolized?

 

Ex. There are fungal and bacterial spore populations of 2000 per cubic meter between 3 to 12 kilometers above sea level. (Microbes and Man pg. 1) And obviously bacteria and fungi are much larger and heavier than molecules.

 

And also with aromaticity - what are we smelling? Like rust for example, that would be iron oxide molecules making it through the air and onto our olfactory receptor cells?

[mytechuniverse]

I'm fairly certain anything that is small and light can be swept up in air currents like dust. The bacteria and fungi make it there the same way. There was a past experiment questioning whether bacteria were made in the air or were falling through the atmosphere. I don't remember details, but I do know that the experiment proved that the bacteria must have been swept up. Moisture gets in by way of evaporation. Almost any amount of heat will allow small amounts of water molecules to be swept up into the air. As far as smell goes, there are many different explanations of varying depth. However, and overview would be that the particulates make it into the mucus and subsequently make it to the olfactory nerve fibers in your head.

[Horza2002]

As you have already staed, the composition of the air is mainly nitrogren and oxygen with a sevreal other gases all mixed in (water vapour, carbon dioxide and argon). IN principle, every compound should be able to exist as a gas...howeve, this is not always the case. Some compounds decompose upon heating (decarboyxylation is beta keto acids is a common example) and so they never get into the gas phase.

 

In addition to the gases that are all mixed up in the air, there are also a lot of particles that are just suspended in the air because they are so light. Bacterial spores are one, dust, pollution all sorts of things can become spread through the air.

 

As for smell, well it could be either of the two processes so far mentioned. If what you are smelling is a gas, then its simple just part of the air that you inhale. However, you can also inhale the small particles that are suspended in the air. I assume that is how you can smell things in the air that are not actually in the gas phase. So for your example of rust smelling like blood (because of the iron it contains) is because there are small particles of rust floating around the air which you inhale and then smell

[John Cuthber]

The "smell of rust" isn't actually the smell of rust.

A clean piece of rusty iron doesn't smell, but one that has been handled does.

The oils from your skin get onto the metal and the rust alters them chemically into other compounds. It is those other compounds that you can smell.

 

(strictly speaking, the rust catalyses the reaction of the oils with air, but the effect is the same as if the rust itself reacted)

[CaptainPanic]

The "smell of rust" isn't actually the smell of rust.

A clean piece of rusty iron doesn't smell, but one that has been handled does.

The oils from your skin get onto the metal and the rust alters them chemically into other compounds. It is those other compounds that you can smell.

 

(strictly speaking, the rust catalyses the reaction of the oils with air, but the effect is the same as if the rust itself reacted)

What about the smell of a train that hits the brakes? The burning iron smell? Isn't that the smell of pure rust aerosols? It's quite a similar smell as an angle grinder cutting through metal. In both cases, there is a metal (probably steel), which is grinded and heated.

 

(If this off-topic question gets more than 1 answer, it may be a good idea to split it off as a separate topic).