Density vs. Specific Gravity

First up we need to look at the difference between mass and weight.

Mass is a measure of an objects ability to resist a change in motion. Mass is constant and under normal circumstances is constant. In the SI system mass is measured in kilograms (Kg).

Weight is the force exerted by a mass when it is under the influence of gravity. Weight is variable and is dependent of the strength of the gravity. In the SI system weight is measured in Newtons (n). The confusion comes from the imperial system of weights and measures where mass and weight used the same units, pounds. Unfortunately this has carried over and may people use Kg to measure force or the weight of an object. An example of the incorrect use is pressure gauges that are calibrated in Kg/Cm². This is a completely meaningless unit and the correct way to state pressure is in Newtons per square meter, otherwise known as Pascals (pa).

Now getting back to you question, as you stated density is a measure the mass of an object has divided by the volume that object occupies. In SI units it is expressed in kilograms per cubic metre (Kgm^-3).

Specific gravity is a measure of the relative weight of a substance when compared to the same volume of water. The specific gravity is calculated by taking the density of a substance and dividing it by the density of water. In SI units we are dividing Kgm^-3 by Kgm^-3 so it has no units.

For example a substance that has a specific gravity of 7.0 is seven times as dense as water and will have a weight 7.0 times as great as an identical volume of water. A substance with a specific gravity of 0.5 is half as dense as water and will weigh half as much as an equivalent volume of water.

In the SI system water has a density of 1,000 kilograms per cubic meter, 1,000 Kgm^-3, so in reality, when you convert the density to specific gravity you are actually dividing by 1,000.

Specific gravity is important when you are trying to calculate buoyancy. If a substance has a specific gravity less than 1.0 then it is less dense than water and will float. If it has a specific gravity greater than 1.0 then it is more dense than water and will sink.

I hope that has helped but if you need further explanation please don't hesitate to ask.

That's a great reply masu . The only thing I could add is that relative density is worked out by comparing the density with water at 4^oC . Its a minor detail , but may be a factor to Guest. (Yes , I'm still annoyed at that challenge question ).

I also agree that Mark is a great engineer and takes lots of pains to write in simple way to be understood by layman. Good.

I asked myself why would they use 4 degrees C. ?? but I will bet that 4 degrees is the coldest that water can get before it begins the transition to ice. Am I correct?

Bill

Not quite Sciesis2. 4°C is used as this is the temperature at which water has its maximum density. Most other liquids get continuously denser as they approach freezing point, the colder layers sink, and they freeze from the bottom up. This anomalous behaviour is why bodies of water freeze from top down, and has had a major impact on evolution of life on Earth.

This Citich1. from PR

I agree with most of all said. In addition the reason why 40C, it's a molecular one due to the polar nature of water (dipole), where hidrogen bonding start to expands at temperature below that and shrinks about that temperature, so at 40C water density is at maximum. D=M/V. And remember expansion occupy more surface area, increasing V, then looking at the formula if you increase Volume, density will decreses.

bye

I am a microbiologist, can find me at citich1@aol.com

Dear Mr. Sciesis2,

The answer for your question is YES.

RAJESWARI.

No, I disagree, see my #12. Water is at maximum density at 4°C, but it doesn't start to freeze until 0°C.

Codey

Dear Mr.Code Master,

I agree with you that at 4 Deg.C, water has minimum volume and has max. weight. Thereafter, below 4 Deg. C, the density starts falling which means the vol.increases, and at Zero Deg. C, water is turned to ice or turning to ice phase. The increase in vol. is linked to formation of ice.

Thanks,

RAJESWARI

Nice reply, Masu. You covered the bases well (yeah, water at a specific temp, pressure, and other specific conditions required of a standard definition, but it is the very lack of such arcana - which adds nothing essential to the discussion - that makes your post especially succinct). Great post, as always! -e

Hello Europium

Why did you select that symbol one to identify yourself? Any specific reason? Never mind, I like the idea. Good.

Thanks. It's in my profile. Click on my avatar.

Nice explanation Masu.

In case French peaple try to read this, they got to be carefull:

In French Density is "Masse volumique" and "Specific gravity is "densité"

Dare I say, only the French could stuff up a system that they invented in the first place.

A new slant on this: if, using a glass hydrometer, I measure the SG of a solution at 95 degC and I get 1.62, is its density 1.62 kg/L? Or is there a correction I must apply since the hydrometer is not longer at its calibration temperature?

This arise out of the installation of a mass flowmeter in our plant, which, on the fluid with an SG if 1.62, consistently reads 1.63 to 1.64 kg/L.

In addition for gases, air is used as reference of specific gravity. For exemple methane has a specific gravity of 0.6 means that it's 6/10 lighter than air.

hope that help you.

I'm dealing w/a ventilation system that requires removal of ethanol vapors at floor level and your answer greatly helped...........its lighter than air.

If you are dealing with powders, the difference between bulk density and specific gravity is the air space between the particle voids.

The larger the particle size, the larger the voids and the greater disparity between bulk density and specific gravity.

Regards, Delmar Schmidt
Melfi Technologies Houston
www.melfitechnologies.com

What are density and specific gravity?

Get a jar. Add a handful of gold nuggets, 1 cup of cooking oil, and fill it up with water. Put a lid on it, shake briskly, and let sit for 37 seconds. Record what happens. Shake it up and try again. Did you get the same response? Why does the gold always settle to the bottom and the oil float to the top? To understand we have to look inside matter and see how it is put together.

Imagine one (1) cubic centimeter of water: if pure and at "standard temperature and pressure" it will have a mass of one (1) gram. The size (1 cm³) is a volume and represents "how big." The mass represents "how much."

Now imagine a cubic centimeter of pure gold, which has a mass of 19.3 grams. The "how big" is the same, but the "how much" has increased by almost 20 times. What about the oil? A cubic centimeter actually has a mass less than 1 gram. For oil, the "how much" is less. Why aren't all 3 substances the same? Clearly there is another factor involved here which relates to "how tightly is it packed at the atomic level?"

We call this new factor "density." Density is calculated by dividing the "how much" by the "how big," and is expressed in grams per cubic centimeter.

How tightly packed = how much / how big

or

Density = Mass / Volume

Specific gravity is the density of a substance divided by the density of water. Since water has a density of 1 gram/cm³, and since all of the units cancel, specific gravity is the same number as density but without any units.

At 4°C pure water has a density (weight or mass) of about 1 g/cu.cm, 1 g/ml,
1 kg/litre, 1000 kg/cu.m, 1 tonne/cu.m or 62.4 lb/cu.ft

Example - Use Density to Calculate the Mass of a Volume

The density of titanium is 4507 kg/m³ . Calculate the mass of 0.17 m³ titanium!

m = 0.17 (m³) 4507 (kg/m³)

= 766.2 kg

SHOOOT, I really wanted to perform that experiment, but couldn't find any gold nuggets. Can I use McDonald's chicken nuggets instead?

Actually, after reading Massu's reply, I thought that the thread is singed, sealed and delivered, NOTHING else to add. not even the remarks on water anomaly. But to my surprise, there are more and more unnecessary replies keeps pouring in.

Gentlemen, The question is answered in full. No need to be a wise-guy.

Wangito.

Oh come now, Wangito d'WiseGuy. If we stuck to that ethic, no one would ever get a chance to read such nuggets as your post about McDonald's chicken..um..nuggets. Btw, those aren't chicken. And they sure as hell ain't gold. Polyvinylroadkill. :-)

Hi Europium

Avoid those organic chemistry names as they make me feel I am eating plastics. Thinking of Sodium and Chlorine makes me think hard to eat salt and I worry that all that Hydrogen and oxygen talk is making me Hydrophobic. I dislike chemistry. Physics is some what tolerable and electronics OK as I never like eating sand even when I am very hungry and there is nothing to eat.

Gold nuggets. Where do you get them? I thought they were toilet of some animal.

Are you threatening to eat me? Yikes! Europium is not organic, that's for sure. I'm inorganic (actually I'm a bona fide Turing machine who passed its Turing Test in '99. Here all along you thought you were talking to a human! hehehe. But think about it: all you've ever seen of me is some characters on your screen, yes?) Gold nuggets are left by Gold(en) Retrievers and Gold Macaws, among others. Be sure to use tongs when you take these gems to the jewellers for assay. Macaws, in particular, can be quite messy. :-) -e

WHY SO MUCH FUSS ON GOLD NUGGETS. IT WAS REFERRED FOR SIMPLE REASON THAT IT IS KNOWN TO ALL AND IT'S SPECIFIC GRAVITY IS ALL THE BOOKS. AS A MATTER OF FACT U THINK OF ANY SOLID ITEM TO UR LIKING WHOSE SG IS KNOWN. IT IS UPTO U.

Posts written in capital letters are the Internet equivalent to shouting. It is considered very bad netiquette to write posts in caps. If you really do mean to shout then please get off this thread.
-e

My daughter KC, (11) says that I shout when I have got nothing to say.

Wangito.

Capital letter are not shouting but are more like barking. Old Teletype were using 5-bit code so only caps were printed. At that time they were time saver as they needed only 60% time to transmit. Transmission was 10 char per second at best and that made it 16 char per second. Today we can transmit at 2.4 Terra Hz. What a change and yet some are locked up with that old time!

Huh? Barking? Ten-character-per-second, five-bit-per-character teletypes used with the Internet? This is relevant? Surely you're not serious!

Proper Internet etiquette - shortened by netizens to "netiquette" - considers messages written in all caps letters as shouting; not barking, whimpering, sneezing, perspiring, coughing or farting. Shouting. This convention has been in force since the early days of the Internet. We're not talking about character limitations forced upon us 1950s-era 50-baud teletypes, Shyam. We're talking about Internet etiquette. Specifically, exclusively Internet etiquette. When was the last time you saw a 50-baud teletype used by anyone connecting to the Internet? Google the word "netiquette." You will not see the word "barking," guaranteed.

-e

The web started with CRT and before that it was only paper tape data memory and bang bang printing. I missed that 50 baud as minimum I used only 110 baud. 5-bit perhaps were also at 110 baud one start and three stop bits no parity. Telegrams were printed in Capital Letters and printed paper tapes were placed on letter sheet fixed with adhesives. Graphics to CRT were added much later. With high resolution of CRTs, the caps are gone and became unpleasant thing. Shouting, yeah when some one replies to your question in caps and Barking when it is all said and has no real meaning or use.

What "web" might that be? Are you trying to tell me that 50-baud teletypes were still used in 1991 when the World Wide Web made its debut, and so much so as to lend any weight at all to your ridiculous assertions?

Caps in posts are the same as shouting, Shyam. Get used to it.

-e

In early developments, web meant only sharing of types information among people, which is close to email in text format. Subsequently images were added and still it was not even Hyper Text.

Your point?

I see what you mean: Al Gore - Father of the Internet - posting birthday wishes to his clandestine sweetheart, a certain Ms. Elvira Flo-Jo, using nothing but CAPS on an Internet backbone server, also invented by Mr. Gore, circa 1998 using parts from a trashed Hugo. They soon parted ways. To quell the ensuing heartache, Mr. Gore invented Quake, which he also developed on this machine using an archaic form of COBOL.

Did you notice the matrix in first rack in the picture you posted and lots of lines in third rack. Those were actually indicator lamps (bulbs) to see if computation is progressing. Think about this technique of looking at computations at GHz clocks and parallel processing machines today working with light and not electric current. In those times, people never trusted the computers and expected them to fail anytime so used to watch binary numbers in those bulbs going ON and OFF. This trend did not last long but was the way people started. I also used to put bulbs when LEDs were not there and needed transistors to drive them. No rack module ever was build without those computation monitoring lamps.

At that time people did not hate caps. In fact there was good chance that small letter may not form imprints and may get worn off by impacts of hammers. Even though IBM build ink jet some time in 1974 it was all bang bang printing all over the world. People hardly knew what fonts would have meant to them.

"Did you notice the matrix in first rack in the picture you posted and lots of lines in third rack. Those were actually indicator lamps (bulbs) to see if computation is progressing."

-----

No, no, no. That's the distributor.

If that is the distributer, is it old enough that it uses points rather than an electronic ignition?

Bill

It's from a Yugo for Pete's sake!

e , one of my preferred insults ( not aimed at your good self , or anybody on cr4 yet ) is " you've got nothing to say , and you're saying it too loud " . Best avoided unless somebody really gets in your face (fisticuffs may follow ).

Kris.

This is all very en"light"ening ... but seems it is getting very grave and dense!

The gravity of the matter is density, specificity? is that a Scientific word from a vague part of the mind ... anyway, etc., etc. does that convey the same message as if it was written in proper grammatical English?

Back to e=MC² correlation with Density ... any thoughts? When it (matter) becomes energy there is miniscule density ... unless confined ...

Thank you.

PS: Quandary ... which "guru" to follow?

This calls for some Levity. Done!

-e

That's a start ... one thought ... gravity becomes levity ... when it is moved through space past the speed of light ... "let there be light" ... any more ? ... we could discover Warp Drive this way ...

Dark Energy moves at the speed of dark. Backward. And "Warp Drive" was the condition of my old computer's hard disk just before it crashed. Btw, white holes emit levity - a form of antigravity (if you don't believe me just watch "Mary Poppins.") You can't get close enough to the event horizon because it won't let you.

Silver writes: "PS: Quandary ... which "guru" to follow?"

-----

Not as difficult as it sounds. "Guru" is just CR4's euphemism for someone who talks too much.

-e

"Not as difficult as it sounds. "Guru" is just CR4's euphemism for someone who talks too much."

Shouldn't that be writes too much rater than talks too much?

Am I the only one here who talks to his computer?

Sridhar has put it together very well, indeed!

Is that him, too?

http://jersey.uoregon.edu/~mstrick/AskGeoMan/geoQuerry7.html

Very Intresting thread.

Nice and clear explanation by both Ms Masu and Sridhar.

If they are faculties, the students with them are lucky people.

One thing like to add is that Specific gravity is also called as Relative density.

R.Thiyagarajan

In my experience with specific gravity, it has always involved liquids... such as the electrolyte in my car battery (is it charged??) or with antifreeze (what temperature will the coolant in my car freeze?). Only once did I have to use specific gravity to calculate volumes in the realworld.

I was anodyzing small of amounts of aluminum, which requires a sulphuric acid solution. Now this was several years ago so don't go using these numbers. The pure sulphuric acid had a specific gravity of something like 1.72. Distilled water (of course) has SG of 1.00. I needed a solution of something like 1.07 SG. Using specific gravities, I was able to calculate how much Sulphuric acid I needed for so much water.

I hope this might help...

Bill

Oh PS What I used for power to do the anodyzing was nothing more than a car battery charger.

Here's a brain teaser;

How will density and specific gravity correlate as you approach the speed of light?

Quick guess is SG stays constant, density → ∞.

That's uncomfortable. SG actually varies with temperature, given that the reference point of SG is water at a fixed temperature. Steam tables would indicate that at temperatures approaching 100degC, water has an SG of 0.984, and that its density is 984kg/m³.

As density → ∞, one passes through neutron star matter towards a singularity. At those locations, who will be around to care what the SG really is (rhetorical question)?

I'm travelling nearly at the speed of light now, but for some reason my ice water still has an SG of 1. Density hasn't changed either. I want my money back. :-)

Thank goodness ice actually floats.

Pinnacle, Apex and Essence Of All Science and All that we SEEK ... is why we are all here:

I think as you pass speed of light Density and Specific Gravity becomes irrelevant ... as Mass/Matter will all diasapear with a "photic bhoom" into pure energy with a blast of energy "strings" (the Strings of String Theory ... the OM/AUM of Vedas - symbol- try Wingding Font " \") ... all ending by reverberating between Dark Matter, Energy and Time ... ..... VEDA's -> Shiva ... Shakti ... Kaal/Kaali ... the One and Same!

I think we, each of us, are eventually going to approach the truth ... the only way to move and cross between various dimensions (multitude of Brahmans and Loks ...) that we are stretching our visions to look at is ... via way of liberated, enlightened ... freed Spirit ("Atman" the non-matter and "timeless" of the Vedas again) ...

Did you know the Vedas that are older than old and is Written down in what we can find so far in our miniscule way is thousands of years old-ago and yet ... shows the EXACT Speed of light 186,000+ Miles per Sec appx. ... and yet we have "discovered" this fact only a few DECADES ago?!!! Try this link (University of Baton Rouge Professor): (click here)

Hope my contribution helps ... otherwise a mind is a terrible thing to waste!

Kirti

I'm sorry, but my karma just ran over your dogma.

Sorry ... it should have been a "Photonic BOOM"

Dang where is that Stephen Hawking guy when you really need him.

He's on holiday in the Caribbean, working on the next book in his "History" series, A Briefer History of Time Than The Last One. (Sneak preview: Ch 1, "Anthropic, Hell - I've Got Religion!").

-e

He's not having a long chat with Jorrie, then?

Any chat with Stephen Hawking is gonna be a long one.

Ouch...

specific gravity is the ratio of density of the product to the density of an equal volume of water at a designated water

I think you meant to write: ... of an equal volume of water at a designated temperature.

In simple terms, your density definition is correct: it is simply how much a hunk of something "weighs" for a given volume. Styrofoam is very low density. Lead is very high density.

Specific gravity just compares the density of something to the density of water. Something with a specific gravity of greater than 1 will sink. Things with an SG of less that 1 will float.

Guest .

I sincerely hope that you have got the answer to your query ..after reading all the above responses , i began to wonder ,,what happened to the real query.

glad if you are not confused.

i am a first time respondant and enjoyed the conversations about specific gravity vs. density. i have a question for the mighty mental masses.

i have a liquid volume of a chemical (103 gallons) with a specific gravity of 1.2-1.5 and a density of 9.2-12.7. the MSDS indicates this chemical is at 55% mixture with 45% water. how do i determine the weight of the total gallons of the material? is it density X volume? or do you use specific gravity to determine the actual weight of the volume?

i understand you can do both, but want to be sure.........HELP........

First off what units are you using. I know in theory it shouldn't make a difference but it helps if you tell us what units are associated with the numbers.

Second your numbers don't make sense.

You stated that it has a specific gravity that ranges between 1.2 & 1.5 while it's density ranges between 9.2 & 12.7 thingamibobs. The problem with this is that they ratios of the lowest to highest should be the same for both the specific gravity and density which they are not.

Ok, the answer is that you can do it either way.

The simplest is to use the density and just multiply the volume by the density as shown in the equation below.

On the other hand you can also use the specific gravity but in this case you then have to introduce a third factor and that is the density of water. As a result the equation has an additional factor as shown in this equation.

However, having said that you then have to allow for thermal expansion. The problem with this is that water doesn't have a constant or linear thermal coefficient of expansion. Water reaches its maximum density at a temperature of around 4°C and expands as temperatures both increase and decrease from this point. That's why ice floats rather than sinks. It also gets worse because the temperature at which water both freezes, vaporizes and reaches maximum density is also dependent on pressure. That's one of the factors why when you get to the bottom of the ocean the water is still liquid even though the temperature is below 0°C.

So, If you utilise the specific gravity of water you need to modify the second equation to account for both the thermal coefficient of expansion of both water and the substance in question. On the other hand if you utilize the first equation you only have to allow for the coefficient of expansion of the substance in question.

Personally I would recommend sticking to the use of the density rather than specific gravity as it makes the whole thing less prone to error.

wow you helped me with my homework! thanks!

Glad to be of service.

To be completely correct, the specific gravity is the ratio of the density of the material over the density of water at the temperature the measurements are made. The density of water is very close to 1 at room temperature, so difference between specific gravity and density will be very small.