Weight Vs. Volume Question
- Thread starter Soft Cars
- Start date
No, the density of oil is different than water.
Also:
https://bobistheoilguy.com/forums/threads/measuring-oil-volume-using-scale-and-density.344705/
https://bobistheoilguy.com/forums/threads/by-weight-how-much-2-cycle-oil-for-50-1-ratio.240025/
https://bobistheoilguy.com/forums/threads/2-stroke-oil-ratio-question.367502/
https://bobistheoilguy.com/forums/threads/oil-density.366363/
https://bobistheoilguy.com/forums/threads/specific-gravity.105293/
Also:
https://bobistheoilguy.com/forums/threads/measuring-oil-volume-using-scale-and-density.344705/
https://bobistheoilguy.com/forums/threads/by-weight-how-much-2-cycle-oil-for-50-1-ratio.240025/
https://bobistheoilguy.com/forums/threads/2-stroke-oil-ratio-question.367502/
https://bobistheoilguy.com/forums/threads/oil-density.366363/
https://bobistheoilguy.com/forums/threads/specific-gravity.105293/
They will both be 4 Fluid Ounces, but a fluid ounce is not the same as a weighted ounce so the measured weight will be different as oil floats on water...but you would probably need some decent scales to measure a weight difference on that volume.
a bathroom scale won't do it but any kitchen scale will: there's about 20 grams difference between the 2
With water, "a pint's a pound the world around". 8 pints in a gallon, so 1 gallon of water weighs 8 lbs.
With gasoline, 1 gallon weighs about 6 lbs.
That difference in density is why water & gasoline separate into layers if you leave them still long enough. And why airplanes have fuel sump drains at the lowest point in each tank. Any water migrates to that lowest point, then when you sump it the water is removed.
With gasoline, 1 gallon weighs about 6 lbs.
That difference in density is why water & gasoline separate into layers if you leave them still long enough. And why airplanes have fuel sump drains at the lowest point in each tank. Any water migrates to that lowest point, then when you sump it the water is removed.
When measuring volume accurately, also consider the meniscus may be convex, concave, or flat not only depending on the fluid but also on the material of the measuring container. The meniscus is the upper curvature of fluid in a container that is caused by surface tension. With a convex meniscus, the top of the meniscus is the correct reading, and for a concave meniscus, the bottom of the meniscus is read. With a flat meniscus, the readings may be taken at the edge of the meniscus. With small volumes, the meniscus must be taken into account.
Last edited:
Good rule of thumb I use all the time for back of the envelope calculations:
First of all, I'm going to reference specific gravity because it's unitless. Density can be measured by any combination of units of mass and volume, but you must specify units. Kilograms per cubic meter are the SI unit, we often use grams/milliter in Chemistry for convenience, but there's no reason why you can't use stones per bushel or any other crazy combination of units. To find specific gravity, you take the density of whatever substance you're measuring and divide it by the density of water. That makes the specific gravity of water 1.00 by definition. BTW, water is close enough to 1.00g/mL for many purposes.
In any case, as said by definition the specific gravity of water is 1.00.
Most non-halogenated organic solvents fall somewhere in the .75-.85 range.
Most halogenated organic solvents are around 1.2-1.5.
Back when I was a Chemistry stockroom manager, among other hats, I'd often help unload the UPS truck. We'd often get solvents in 20L metal cans, which is a bit over 5 gallons. We would order them for the stockroom(especially acetone) and research groups would often do bulk orders a few times a year. There could be times where there would be 10-20 cans of solvent in a shipment. BTW, shrinkflation and all that, a few years back a lot of companies downsized to 18L to hold prices. 18L is almost exactly 5 gallons.
For a lot of the common lab solvents that would get ordered this way-acetone, methanol, hexane, ethyl acetate, toluene, etc a 20L drum would weigh about 35lbs. Dichloromethane and Chloroform would be more like 50-60lbs. Suffice to say if you weren't looking at the labels, you'd KNOW when you picked up a drum of halogentated solvents(and considering that most just had a simple wire bail handle, they weren't the most comfortable thing to carry). We'd also get 200 proof undenatured ethanol in 5 gallon plastic bottles, but that came through a different source(to be able to get it tax free).
As said too, density has nothing to do with whether or not something will mix with water. I'm aware of 7 common organic lab solvents that are miscible(will mix in any proportion) with water. Those 7 are methanol, ethanol, isopropyl alcohol, acetone, dimethylsulfoxide(DMSO), acetonitrile, and tetrahydrofuran(THF). They're not usually cited in "misbilitily" lists, but I'm pretty sure the small poly-ols like ethylene glycol, propylene glycol, and glycerin are also. The key with all of these actually is that they are able to hydrogen bond readily with water, and their non-polar portions aren't so large as to prevent this.
Most other common solvents-especially hydrocarbons-are too non-polar. With that said, there's often SOME degree of water solubility especially with things with some ability to hydrogen bond like diethyl ether. Density does determine which layer is on top when two things form a biphasic mixture-non-halogenated solvents generally are on top of water, and halogenated are on the bottom.
First of all, I'm going to reference specific gravity because it's unitless. Density can be measured by any combination of units of mass and volume, but you must specify units. Kilograms per cubic meter are the SI unit, we often use grams/milliter in Chemistry for convenience, but there's no reason why you can't use stones per bushel or any other crazy combination of units. To find specific gravity, you take the density of whatever substance you're measuring and divide it by the density of water. That makes the specific gravity of water 1.00 by definition. BTW, water is close enough to 1.00g/mL for many purposes.
In any case, as said by definition the specific gravity of water is 1.00.
Most non-halogenated organic solvents fall somewhere in the .75-.85 range.
Most halogenated organic solvents are around 1.2-1.5.
Back when I was a Chemistry stockroom manager, among other hats, I'd often help unload the UPS truck. We'd often get solvents in 20L metal cans, which is a bit over 5 gallons. We would order them for the stockroom(especially acetone) and research groups would often do bulk orders a few times a year. There could be times where there would be 10-20 cans of solvent in a shipment. BTW, shrinkflation and all that, a few years back a lot of companies downsized to 18L to hold prices. 18L is almost exactly 5 gallons.
For a lot of the common lab solvents that would get ordered this way-acetone, methanol, hexane, ethyl acetate, toluene, etc a 20L drum would weigh about 35lbs. Dichloromethane and Chloroform would be more like 50-60lbs. Suffice to say if you weren't looking at the labels, you'd KNOW when you picked up a drum of halogentated solvents(and considering that most just had a simple wire bail handle, they weren't the most comfortable thing to carry). We'd also get 200 proof undenatured ethanol in 5 gallon plastic bottles, but that came through a different source(to be able to get it tax free).
As said too, density has nothing to do with whether or not something will mix with water. I'm aware of 7 common organic lab solvents that are miscible(will mix in any proportion) with water. Those 7 are methanol, ethanol, isopropyl alcohol, acetone, dimethylsulfoxide(DMSO), acetonitrile, and tetrahydrofuran(THF). They're not usually cited in "misbilitily" lists, but I'm pretty sure the small poly-ols like ethylene glycol, propylene glycol, and glycerin are also. The key with all of these actually is that they are able to hydrogen bond readily with water, and their non-polar portions aren't so large as to prevent this.
Most other common solvents-especially hydrocarbons-are too non-polar. With that said, there's often SOME degree of water solubility especially with things with some ability to hydrogen bond like diethyl ether. Density does determine which layer is on top when two things form a biphasic mixture-non-halogenated solvents generally are on top of water, and halogenated are on the bottom.
I would be happy to be proven wrong, but mercury is the only liquid I know of that gives a convex meniscus in glass or plastic...
I have no intention of proving you wrong. I will add that the meniscus of a fluid may change from concave to convex if we talk about fluid in a container/tube with a very small diameter.
Last edited:
That's a good rule of thumb for U.S. gallons, but doesn't hold for the larger Imperial gallon:
1 U.S. gallon of water = 8.33 lbs
1 Imperial gallon of water = 10.0 lbs
(Which makes sense, as a U.S. gallon is about 5/6 of an Imperial one. When a Canadian tells you his car gets 30 MPG, figure on 24 MPG in American units.)
While we're getting all sciencey... if you mix 100 mL of water and 100 mL of methanol together you get about 195 mL total and it gets a little warm. It's a pretty cool phenomenon.
Bunnspecial makes an excellent post above. When I worked in the lab, you could easily tell the difference between a gallon bottle of methanol, water, at methylene chloride. Mentioned by Bunnspecial was DMSO. DMSO is some weird stuff. It freezes at 65°F. And it freezes into large crystals. A lot different than how water freezes.
Bunnspecial makes an excellent post above. When I worked in the lab, you could easily tell the difference between a gallon bottle of methanol, water, at methylene chloride. Mentioned by Bunnspecial was DMSO. DMSO is some weird stuff. It freezes at 65°F. And it freezes into large crystals. A lot different than how water freezes.
Definitely an oddball one and one I've admittedly not worked a ton with.
Every few years it seems to resurface as a miracle arthritis/joint pain cure. That's all good and well, except for how well it dissolves so many other substances and how readily it is absorbed through the skin. I'm always afraid of what else it may carry along with it rubbing it on your skin...
I will ask my rent subsidized neighbors if I can borrow a gram scale
If you want to get more in the weeds take a look at manufacturers product data sheets. For example. Mobil1 0W-20 AFE has a density of .8454. In other words, while a liter of water weighs 1,000 grams, a liter of 0W-20 weighs 854.4 grams. All motor oils have a density in this general neighborhood.
As a practical example, this is why oil slicks float on top of water and don’t sink.
As a practical example, this is why oil slicks float on top of water and don’t sink.
A gallon of water weighs 8.35 pounds. A pint weighs 1.041 pounds. Until a few years ago I thought the old a pints a pound was correct. Nope.
8 lbs. per gallon or 1 lb. per pint is correct enough for most usage.
If you want to be more precise, 8.35 ain't correct either because the weight of 1 gallon of water depends on the temperature.
I will ask my rent subsidized neighbors if I can borrow a gram scale
It's about half an ounce, any kitchen scale will tell the difference
I have a fuzzy memory of a Model Garage story in Popular Science wherein Gus Wilson confounds the town grump, Silas Barnstable, by mixing water and alcohol-based antifreeze, and getting less total volume than the sum of the parts.
It's obviously an old story, as "permanent" (ethylene glycol- based) antifreeze has been around for a long time.
