Its for my science.
2007-09-22 06:06:19 · 7 answers · asked by H T 1 in Science & Mathematics ➔ Physics
Ideal gas law: PV = NkT
PV = mkT
N times atomic weight = mass
density = atomic weight * P / kT
I'm guessing you want to MEASURE the density.
To calculate the density, you have to know the mix of each kind of mollecule. If you know that, the calculation is fairly easy.
Anyway, if you double the pressure isothermally, you double the mass. Measure this mass difference.
Or you could double the temperature isobarically, so you halve the mass.
Or just take pressure to zero, so you have no mass (which is what Raymond suggested above, which is the easiest calculation).
Anyway, measure the mass difference after messing with P or T in a controlled way, and then you can easily calculate density.
2007-09-22 06:32:52 · answer #1 · answered by Anonymous · 1⤊ 0⤋
Density =mass/volume.
You could take a sample of air in a container you know the volume of, determine the mass and divide to get the density.
Since it is a gas, it is very compressible and so the density changes. It changes with barometric pressure, humidity, pollution. going up a mountain decreases the density, since gravity is not holding it down as much.
2007-09-22 06:17:36 · answer #2 · answered by science teacher 7 · 0⤊ 0⤋
You don't specify whether you want a calculation or a measurement. I'll assume the latter. One neat way is to exploit the buoyancy of water in air. Yes, I wrote that right. Distilled water at 20C (you'll want to check that) has a density of precisely d0=1g/cm^3 because the original definition of a gram was the mass of 1 cm^3 of water at that temperature. However, if you *weight* volume V of water at that T very precisely (think triple beam balance) in 1 atm of air, its gram-weight per unit volume will be d0-d1, where d1 is the density of air. This is due to the fact that the water displaced air of weight d1*V when it was poured into the container.
2007-09-22 06:45:26 · answer #3 · answered by Dr. R 7 · 1⤊ 0⤋
One way is to have a rigid hollow body from which the air can be removed.
Find the volume of the hollow (by measurement or by filling it with water and measuring the volume of water that it contains). Then (after removing the water and drying), weigh the container full of air. Remove the air, weigh again.
Difference should be the weight of air. Divide by volume.
In the old days, they would do this with large hemisphere of metal (e.g., bronze). One hemisphere had a valve allowing a tube to be connected to a vacuum pump.
One favorite "public demonstration" was to have teams of horses pull, in opposite directions, on each hemisphere, to show that air pressure was stronger than horses.
2007-09-22 06:14:16 · answer #4 · answered by Raymond 7 · 1⤊ 0⤋
Atomic mass of air molecules = grams per mole
1 mole is 22.4 liters at STP
Atomic mass in grams / 22.4 liters
Like if it was Oxygen. It would be 32grams per mole. That's because it's diatomic so it's really O2.
Density of Oxygen = 32 grams(1liter/1000mL) / 22.4liters
Density of Oxygen = 1.43^10grams/mL
Which is 0.00143g/cm^3
That's 1/700 of the density of water so I agree with helen m, also.
2007-09-22 06:27:57 · answer #5 · answered by Anonymous · 0⤊ 0⤋
The density of air is about 800 times less than the density of water, which is about 1000 kg/m3 (1 g/cc).
2007-09-22 06:14:24 · answer #6 · answered by helen m 3 · 2⤊ 2⤋
i don't think you can. it can take different shapes and sizes so it's impossible.
2007-09-22 06:12:37 · answer #7 · answered by Anonymous · 0⤊ 3⤋