CO2 - Dumb question

Chemistry - CO2 is heavier than air.

Humans need some oxygen to breathe.

The planet is overheating as CO2 contributes to absorbing heat from the sun ?

So if there is so much CO2 and it is heavier than the air (containing the oxygen we breathe), how come that we are not wading around in CO2 and unable to breathe, if it is lower down, why aren't valleys full of CO2 and that we are dropping like flies? I know there are cases of "poisoned" valleys in some parts of the world - but why not all over the place ?

Bob

Diffusion.

Not a dumb question. However there is clearly enough stirring or molecular interaction going on to ensure that the atmosphere remains mixed as you acurately observed. I would say that the important values for the molecules concerned are the molecular weight and the kinetic diameter (the effective size of the molecule when considering collisions with other molecules). For N2 CO2 and O2 in that order the atomic weights are 28, 44 and 32. and kinetic diameters are 364, 330 and 346. All within a factor of 2 by weight and much closer than that in diameter. At ground level the temperature is highest so the average kinetic velocity of the molecules will be highest too. This along with the fact that the density is highest would suggest that the max rate of collisions occurs at ground level and gradually tails off by height. One would expect in the upper atmosphere when density and temperature is very low layering would indeed take place. In the extreme case of helium the atmospheric kinetic interactions are such that helium can exceed the escape velocity of the earth and so leech out into space.

Well that's my take on the subject purely by thought.

regards Martin

Good afternoon, Bob and Mark,

Carbon dioxide will diffuse in time, given the right energy and freedom of space. But it can build-up in other circumstances.

Bob, I think you sort-of referred to the case in Africa where some sort of volcanic activity sent a great quantity of undiluted carbon dioxide up through the bed of a lake. The lake water was retained by a natural dam and was at the top of a valley. Before it had time to diffuse, the mass of carbon dioxide, being heavier than air, spilt over the dam and flowed down the valley as an invisible cloud. It passed through a village, suffocating all the inhabitants, both human and livestock, all before it had the time and conditions to diffuse. It's diffused by now - every breath you take could contain a molecule or two of the carbon dioxide that came up through that lake!

Carbon dioxide build-up can be a danger in SCUBA equipment. Human exhalations contain lots of carbon dioxide. With the Cousteau-Gagnan Aqualung, the wearer breaths through a mouthpiece and the nose and eyes are separately covered by the diving mask. One-way valves in the breathing tubes achieve adequate 'traffic control' so you don't breathe in what you've just breathed out. Back in the 1960s/1970s there was a full face-mask, I forget the maker's name. With that gear, the wearer still breathed through a mouthpiece but wore a nose-clip to avoid breathing in any carbon dioxide build-up that might accumulate in the larger volume of the face-mask.

Best regards,

Swarf, Mostly!

P.S.: I see that Martin and I were typing at the same time.

Best regards, S,M!
 

Edited By Swarf, Mostly! on 10/08/2022 14:06:06

It's because they are panicking over insignificant amounts of a trace gas

Four hundredths of one penny

Most valleys anyway are open at their outlets, to a plain or the sea, so won't trap CO2. It might happen in a closed depression with steep sides and fairly small area, but even there the winds are normally enough to disperse it.

Also, a lot of the gas is absorbed and used chemically by plants, or dissolved into water and by the dissolution of Calcium Carbonate rocks.

Carbon dioxide is indeed heavier than air, but with the natural movement of air and ventilation it is readily dispersed.

It can become a major problem in confined spaces, look up Carsington Dam in the UK, four deaths in a inspection chamber, due to acidic water reacting with limestone producing co2.

I used to teach confined spaces and there are lots of horror stories involving co2.

Nothing to worry about in normal atmospheric conditions

IanJ

I know from other threads that it's not the done thing to question things, but here goes:

By what mechanism does CO2 hold onto heat energy over & above other gases in the atmosphere?

How much more CO2 is in the atmosphere now and how much should there be?

If CO2 is capable of absorbing energy, shouldn't we be looking at ways to use this feature to harness energy from the Sun?

If CO2 is helping to destroy the planet, then an obvious cause must be due to the massive consumption of beer, larger, and any kind of CO2 powered fizzy drink, so doesn't it sense to ban these products?

Martin.

The CO2 used in fizzy drinks is a by product of other industrial processes, so banning fizzy drinks won't help. I doubt that the CO2 produced by fermenting barley, grapes etc to make booze figures large in the scheme of things. My local coal fired power station burned 16000 tons of coal per day, the average holiday flight emits the odd ton per passenger. No doubt someone will come along and explain how, but it is beyond doubt that CO2 has increased massively since we started burning fossil fuels big time, and all reputable scientists agree it causes global warming. Just because I don't understand how doesn't mean it's not true.

OK here is another one, why is water not a gas at room temperature? CO2 is and it is a heavier molecule.

regards Martin

Hi, you may find answers here Greenhouse Effect

Regards Nick.

The heat seems to arrive spasmodically as an upwelling of warm water in the Pacific which is called an el Nino event.

The "scientists" don't explain how the greenhouse heat gets from the troposphere down to the bottom of the Pacific without warming the troposphere.

I am wondering if YouKnowWho might be involved?

Don't see the relevance, sodium hydroxide has a lower molecular weight than CO2 but it's a solid at room temp.

Tungsten hexafluride has a pretty high molecular weight, but is a gas, and Radon is really heavy, although it isn't molecular, being a noble gas it is atomic

Edited By duncan webster on 10/08/2022 15:17:52

There is water in the atmosphere. If it goes away then more water evaporates from the surface. It tries to maintain what they call a partial pressure.

If CO2 drops below 150ppm then it no longer exerts sufficient partial pressure to pass through plant cell membranes and we all die.

Not so much storing as trapping. The way it goes is this. All molecules have an absorbtion spectra comprising of strongly absorbing wavelengths interspersed by non absorbing bands. Visible light from the sun reaches the ground through the largely transparent atmosphere causing heating. The warm ground is re-radiated in the Infra-red back up into the sky. Greenhouse gasses are gasses that absorb in the Infra-red so increasing the amount of these gasses in the atmosphere will absorb and then re-radiate this energy back to the ground rather than let it dissipate into space. So increasing greenhouse gasses like CO2 and Methane will make the atmosphere increasingly more opaque to IR wavelengths trapping that energy on the planet and causing a global heating effect. Making the atmosphere less opaque or more transparent to IR re radiated energy will conversly reduce the net energy budget and the planet will cool to equilibrium. Thats the how.

By observation CO2 levels around 300 parts per million put the earth in a stable zone where climate is able to be regulated by plant growth and CO2 draw down by the sea and its organisms. Push the levels too high or too low and you get a major warming event or and ice age which severely disrupts the biosphere destroying the regulating factors that have kept the climate comfy for the last umpteen thousand years.

regards Marin

Whatever happened to the hole in the ozone layer? And was (is, if it's still around) it a bad or a good thing as regards global warming?

Rob

By what mechanism does CO2 hold onto heat energy over & above other gases in the atmosphere?

Lots of gases do it - absorb infra red electromagnetic waves. Water (vapour) and methane are the other main absorbers. The reason why they are ‘greenhouse’ gases is simple enough - when they eventually let go of that energy collected from infrared from the Earth, it is re-radiated in all directions, a large proportion of that radiation will be directed downwards, back to the Earth below.

Of course, as the Earth’s atmosphere warms it will hold more water vapour, but it is the methane and carbon dioxide released by the human population (burning fossil fuels and farming more herbivores, in particular). It is the three-fold increase in CO2 that is considered the number one problem gas.

By the way some on here mix up atomic masses and molecular masses.

Water is an anomalous compound - it is a liquid at our normal temperatures because of hydrogen bonding. Its other useful characteristic is the fact that its density is at a minimum of 4 degrees Celsius while it freezes at 0 Celsius. If ice formed at the bottom of water courses, the rammifications for life on the planet would have been much different.

Water is a polar molecule, you can attract / repel a gentle stream of water from a tap with an electrically charged rod. These charges create hydrogen (weak) bonds between molecules. These explain why ice floats and why water is a liquid rather than a gas, which you might expect at room temp. .
These hydrogen bonds in water make life possible.

Raised CO2 levels and rising temperatures will not destroy the planet. Historically the atmosphere was very different. The evolution of photosynthetic organisms resulted in a huge rise in the oxygen content of the atmosphere. As a result those organisms had to protect themselves from the toxic oxygen. They either evolved to survive in an oxic atmosphere, occupied anoxic niches or died out. Life and the planet will survive, but many organisms will die out.
It really annoys me everytime I hear / see someone say that raising CO2 levels will destroy the planet - I am amused by their lack of understanding.

Spot on. I only raised the question to demonstrate that asking simple questions leads to more complex understanding when you find the answers. It was however not my question but one that JD Bernal asked himself staring out at the fog when stranded at an airport. It led him to produce a seminal paper on the structure of water.

regards Martin