So, dry air weighs 34,093.48 mg per cu.ft.
Which is about 1.2 ounces per cu.ft.Observation:I think the above is what you would find if you weigh the air in a vacuum (the air is in a container of known weight, and the container is being weighed in a vacuum). The above was probably determined with knowledge of physics and mathematics, but the idea is the same. Practically speaking on earth's surface, at 20 degrees C and one atmosphere, the air would weigh nothing at all; perhaps more accurately the air 'weighs' its own displacement in the air itself. It would be perfectly buoyant. Think about weighing 1 cubic foot of lake water, with the water completely submerged under the surface of the lake... quite a different result from weighing it on dry land. Unless you are studying buoyancy, it might be more useful to use things like atmospheric pressure, or the mass of a sample of gas and its temperature and pressure within the sample, depending on your need. The question demonstrates the importance of knowing the standard conditions (stp) used in research. There is no universally established set of standard conditions, so attention is absolutely necessary. See discussion. Follow-up to observation:If you had a container with a volume of one cubic foot and evacuated it, it would weigh less than if it were full of air at standard temperature and pressure. You would not need to weigh it in a vacuum, unless its weight in vacuum is what you want.
By comparing the weights of the evacuated and the full container, you can determine the weight of the air, essentially, in a vacuum. The weight of the air "in air" remains zero. This seems odd, because we are weighing the container "in air", and the weight goes up when we add the air. I think this does not mean that the air weighs something as it hangs out in the air. [see discussion]
I think what is happening is that the observed weight of the perfectly evacuated container at one atmosphere will be less than the weight of the container itself, because to find the container's weight we would need to subtract the weight of the volume of air the whole container is displacing. So putting mass into the container serves the purpose of bringing us closer to the weight of the container, and doesn't demonstrate that the air has weight while suspended in itself. [see discussion]Any chemist will tell youthat the molar volume is 22.4 liters at STP - Standard Temperature and Pressure (1 atmosphere, 32 F). The mass of a mole is equal to the molecular weight of the molecule it's made of, multiplied by 1 gram.
Air doesn't have a standard definition as to composition, but it's generally about 78% nitrogen, 21% oxygen, and 1% other stuff. Since nitrogen has a molecular weight of about 28 and oxygen has a molecular weight of about 32, the molecular weight of air is about 28.8 and a mole has a mass of 28.8 grams.
Dividing 28.8 grams into 22.400 liters, you get 1.286 grams per liter, which isn't far from the 1.2 grams per liter quoted above, which is not at STP.
Arguing that air "weighs nothing" in ordinary conditions ignores the fact that air may be used to displace other fluids, and ignores the fact that air's weight gives air momentum.
Or consider the lift of a hot air balloon. If the temperature of the air in the balloon is 200F and you are ballooning on a winter morning when it's 40 out, how much lift does the balloon produce. You need to use absolute temperatures so adjusting to Rankin scale, the air inside the balloon only weighs 499/659 as much as the air outside the balloon. That's about 75% as much - and so the lift of that balloon is about 25% of the weight of the air that would normally be in that balloon. Hmmm. A back-of-the-envelope calculation reveals that 25% of nothing is still nothing - and yet hot air balloons DO rise.
One might as well assert that you only weigh 85 pounds, because you're only 85 pounds over the Metropolitan Insurance tables, but you'll still have to buy your clothes in the Big & Tall store.
a cubic foot of air weighs 7 grams
Everything I can find says that a cubic foot of air can lift about 62-63 lbs.
1 cubic foot of air will support 62 lbs
Weigh, implies a spring scale, answer would be zero. How much mass does 100 cubic feet of air have would be a better question.
The weight of styrofoam depends on the density of the styrene hydrocarbon from which it is manufactured and the volume of air bubbles trapped in the foam.
The answer depends on the density of the material. A cubic yard of air will weigh somewhat less than a cubic yard of lead!
More info needed. How much does 0.4 cubic feet of what weigh? Air? Lead? Water? Dirt?
No. Not at all. Volume has no force. Put 1 cubic foot of air inside a sealed jar, and weigh the air. Now let the same air into a 10-cubic-foot jar; seal the jar, and weigh the air again. The air has 10 times the original volume, but it still has exactly the same weight.
2 cubic feet
0.0014 to 0.0015 pound weight per cubic inch.
One cubic metre of what? Air weighs almost nothing; one cubic metre of osmium would weigh more than 22.6 tonnes.
Molecules or moles? And in a cubic foot of what? Air?
One cubic foot is 28.32L
It turns out that square feet are a measure of area and as such are two-dimensional quantifier. A square foot of anything will weigh nothing because the material, the air or lead or anything else, will be 12 inches long by 12 inches wide by zero inches thick. If it was a cubic foot of air, i.e., a volume of air occupying a space 12" x 12" x 12", it would weigh about 0.08 pounds at standard temperature and pressure.
no if there is no air in the container (a vacuum) to begin with the addition of air will add mass to the container. air weighs roughly .0807 lbs per cubic foot
1 cubic foot = 1,728 cubic inches 1 gallon = 231 cubic inches = 0.13368 cubic foot 5 gallons = (5 x 0.13368) = 0.6684cubic feet, of anything, even empty space
This mass is 1,2 mg at 20 0C and 760 mm col. Hg.
It all depends on what you have in the cubic feet. -- If the cubic feet are full of air, they weigh about 8 pounds. -- If they're full of water, they weight about 6,243 pounds (3.1 tons). -- If they're full of lead, they weigh about 70,793 pounds (35.4 tons). -- If the cubic feet are completely empty, they weigh exactly zero.
At sea level and 15 deg C, the weight of a cubic metre of air is approx 11.0 Newtons.
If you take the average weight of all of the molecules in one cubic foot of air and add them together you reach 0.0807 pounds. This number can fluctuate with temperature and variations in the composition in the air.