Talk:Density/Archive 1

Early comments
The article says that densities should be specified in kg/m3 - yet the table of sample densities are in g/cm3. This is not a good thing! The numbers need to be 1000 times larger and the units at the top of the table changed.
 * Actually, one ten-millionth, which is 10-7. (I fixed your tags.) Vicki Rosenzweig


 * Would someone please add an entry for ice? Thanks!  Aspie 23:38, 4 October 2005 (UTC)

SteveBaker says: The generally accepted figure is 917 kg/m3 - but density varies with temperature. I presume the table in the article is for densities at room temperature - and you can't say what the density of ice is at room temperature! but, it is possible. hahaha

density=mass/volume.< remember that...if u can..(rose)penis

andre **** you. **** your mother, dog, father, sister, brother and all your family and maby myself too if thats ok . Water isn't really defined to have density 1 is it? That's a schoolboy definition. --drj

Mayhaps, I certainly was a schoolboy once :-) The fact that one litre of water weighs exactly one kilogram os no accident however. The SI units were chosen carefully, although i know not if the metre or the kilogram was defined first (my money is on the metre), the relation between them is indeed found through the density of water (at 4 degrees celsius if memory serves correctly). --Anders Törlind.

Oh, by the way, is the kilogram still defined as the lump of platinum they hold in Paris, or is it defined as a certain number of atoms of something? --Anders Törlind

I wondered about this recently. My research confirms what kilogram says. There is a standard mass made from platinum/rhodium. I guess it is too difficult to define it as the number of atoms of something. --drj

Meter was defined 1791 by the French Academy of Science first the kilogramm 1889, so meter was a way earlier defined (but it depends what definition of meter or kilogramm you prefer to be the first correct one). The definition of meter has changed a bit over time, the definition of kilogramm is the same since 1889. Information taken from: http://physics.nist.gov/cuu/Units/current.html -- Tom B.

I believe that the metere was originally defined to be 1x10-6 of the distance from the equator to the north pole via a line that went through Paris, this was mesured incorrectly at the time, so the distance is somewhat different. The other units as far as I know are based on that. The kilogram was originally based on a cubic decimeter of water, but that is much too variable to be used as a reference.-- mike dill
 * Actually, one ten-millionth, which is 10-7. (I fixed your tags.) Vicki Rosenzweig

Do you have the reference for the platinum density of 21.09? According to http://hypertextbook.com/facts/2004/OliviaTai.shtml, the density is 21.45 and they list 5 references. When I Google platinum density, the first entry webelements.com (another wiki) agrees with 21.09, but going on down the list several pages, everyone else says from 21.4 to 21.5. If you change to 21.45 then change the Wikipedia platinum article also. Art LaPella 05:04, Aug 22, 2004 (UTC)

I have checked the CRC Handbook of Chemistry and Physics (60th edition, page B-106) and it gives 21.45 at 20 degC: so have changed here and on the platinum page. --GPoss 06:36, Aug 22, 2004 (UTC)


 * For the record, the 21.09 value apparently originates from Lange's Handbook of Chemistry, McGraw-Hill (also cited by WebElements, and standing rather lonely among the other references). Femto 12:00, 14 July 2005 (UTC)

Osmium vs Iridium
It seems the articles for Osmium and Iridium give different values for the density of Osmium compared to the value in the density table, affecting the order of the elements in the table. Apparently Osmium should be listed at 22661 kg/m³ rather than 22610 kg/m³. --Vinsci 14:48, 4 Apr 2005 (UTC)

--- It looks like those two articles now both explain that the difference in density between Osmium and Iridium is so small that it takes theoretical calculations of density to tell the difference between them. This article is far too definitive about Iridium being the densest. The language should be loosened somewhat.

Table salt density
What is the density of table salt (in grams per cubic centimeter)?

Can anyone put more information on this page i need more information!! thnx :D


 * Please see the sodium chloride page, to find your answer.

Nonsense
There is a non sequitur at the end of the "Measurement of density" section: "this site is extremly good for finding scientific info." Is this supposed to be turned into something or should it just be deleted? Epugachev 06:32, 28 February 2006 (UTC)
 * Gone. Femto 12:05, 28 February 2006 (UTC)

I need help!!
Does anyone know why egg float in the salt water and how?

The salt in water is much denser than the yolk in the egg. Thus making it float. 04:23, 16 February 2007 (UTC)

"Relative density(specific gravity) of salty water is higher than normal water. For example salt water is ~1.025 whereas water is 1. Arcemedaes principle says that the net upthrust on an object = the weight of fluid displaced. i.e. in salty water this is a number larger than the weight of the egg. As a side note, you can tell if an egg is bad because it floats in fresh water. This happens because air travels to the bacteria through the porous shell and they respire, lowering the overall density.(no citations, I don't have any)" (James Pipe 19:04, 28 February 2007 (GMT))

Unit term style
Regarding the recent 'corrections', neither style is incorrect. The term a · b&minus;1 is equivalent to a/b. While this makes little difference for kg/L, I think in the general case a consistent exponential style kg · m&minus;1 · s&minus;2 would be preferable over a proper fraction $$\frac{kg}{m \cdot s^2}$$. Femto 17:44, 28 March 2006 (UTC)

HOW DO YOU MEASURE DENSITY ??? and what tool do you use??

weak width
how do you measure density and what tool do you use??

help
density and the knetic theory

in other language : french
The link to the french page is wrong : in french the "densité" stands for a ratio and doesn't have a unit whereas is has one in english. The link should led to http://fr.wikipedia.org/wiki/Masse_volumique, which is what the french call "density".you also can link to http:www.brainpop.com/science/matter/massvoldensity/index.weml

Measurement of density
The section on the measurement of density doesn't make sense

It currently reads

For substances other than solids, the density can be found by measuring the dry weight ( Wd ), the wet weight ( Ww) and submersed weight ( Ws), usually in water.

The phrase "For substances other than solids" surely means liquids and gases whose density is certainly not measured by the immersion method described and the term wet weight is not defined.

I had changed this to

For irregularly shaped solids, the density can be found by measuring the dry weight ( Wd ), and the weight when the object is submersed ( Ws), usually in water.

Leaving aside the fact that submersed is not a word, this describes the Archemedian method of measuring the density of an irregularly shaped object.

Comments please

John Loveday

Yadevol 09:32, 19 February 2007 (UTC)yadevol

Now removed this since nobody respondedYadevol 15:46, 24 February 2007 (UTC)yadevol

iVan asks:
does anyone know how to increase/decrease density? —The preceding unsigned comment was added by 138.123.134.102 (talk) 13:34, 23 February 2007 (UTC).

You can do this by changing the pressure Yadevol 15:46, 24 February 2007 (UTC)yadevol

I have now added a section on thisYadevol 16:22, 24 February 2007 (UTC) yadevol

how is density related to gravity?

The relationship between density and gravity is illegitimate. Considering their popularity, it's amazing how they've eluded tabloids all this time. -71.193.200.17 03:30, 22 March 2007 (UTC)

What is density?
It's a silly question, but it's even sillier that the basic question of what density actually is isn't addressed in the article. I don't think it has to be long, just one or two sentences should do. I'd write it myself, I'm not sure how to word it which is somewhat shameful since I'm a math/science student, haha. SunsetFlare 14:16, 13 May 2007 (UTC)

Lead says "In physics, density is mass m per unit volume V", which seems fairly straightforward...a bit technical but hard to be less so and have any semblance to the actual real meaning. Then the next sentence says that "For the common case[...]" it is mass divided by volume, which seems pretty good for common school projects and related uses. What's missing or what needs more work here? DMacks 20:52, 14 May 2007 (UTC)

I think SunsetF has a point. A casual reader, not comfortable with physics, math, or the word "mass", who comes to this article will soon leave in frustration, none the wiser. The only cure for this would be to start with very simple language, along the lines of "density means how heavy something is compared to the space it takes up. If something is small and heavy, like a rock or a lump of lead, it is very dense.  Something light like foam has low density.  Even a very large, heavy piece of foam still has low density, because it takes up so much space."

From a pedagogic point of view, the Archimedes story may be unfortunate. Readers who do not understand the base concept will just be further befuddled by an example of an object which is not a uniform solid. In fact, it is a Bad Thing to have this example in the article without pointing out that the crown actually has two densities -- the density of the material it is made of, and the much lower density of the crown (and enclosed air) considered as an ordinary object. -69.87.202.85 —Preceding unsigned comment added by 69.87.202.85 (talk) 17:58, August 29, 2007 (UTC)

A note should be made regarding the density of non-gasses in the change in density section. Boyle's law is provided, but this is not valid in other phases. I do not have any reference material that suggests what the formula would be. I'd assume it goes like V=(kT)3 where k is the coefficient of linear expansion of the material (thus density - rho = (kT)-3). I was initially confused looking at the tables for water until I realized I was trying to use the wrong formula.

--Astrobit (talk) 04:51, 17 April 2008 (UTC)

Water density no longer exactly one?
For a long time, 1 cc of water at 4-deg C weighed 1g by definition. Assuming that the 999.9750 figure shown in the article is correct, it should have an asterisk, footnote etc explaining the why and how it has drifted off from being exactly one.-69.87.202.85 17:39, 29 August 2007 (UTC)

accuracy of measurements went up. —Preceding unsigned comment added by 70.126.174.93 (talk) 00:43, 17 May 2008 (UTC)

Add non-physics lead sub-section

 * Common meaning:

Density means how heavy something is compared to the space it takes up. A small and heavy object, such as a rock or a lump of lead, is very dense. Something light like foam has low density. Even a very large, heavy piece of foam still has low density, because it takes up so much space.


 * Technical definition:

In physics, density is mass m per unit volume V. For the common case of a homogeneous substance, it is expressed as:
 * $$\rho = \frac {m}{V}$$

where, in SI units:
 * ρ (rho) is the density of the substance, measured in kg&middot;m-3
 * m is the mass of the substance, measured in kg
 * V is the volume of the substance, measured in m3

- OK, I was bold (see previous discussion). I think this is a much-improved multi-user-level lead, but I don't expect it to last long. I don't think WP has much tradition of explicitly catering to a wide range of user levels. I can only beg you to be open to considering that this really is an improvement over the previous nerd-intensive lead. And please find ways to make it even better, instead of just letting it revert to what it was. -69.87.199.135 17:35, 30 August 2007 (UTC)
 * I'd love to see multiple definitions or a definition accessible to multiple audiences—density is an important concept for people at many levels of expertise. I took a whack at integrating your additions. My goals were to have coherent prose (not bullet-points, suggesting distinct or different meanings), to begin with at least a bit of the actual definition (per WP:LEAD) with specific (not casual terminology) writing, and to mix it together so we didn't swamp newbies with equations before giving an accessible hint about what we're talking about. DMacks 19:12, 30 August 2007 (UTC)

If it measures 50Kg per cubic meter, the density is NOT 50. It should be 0.05 (50 Kg/1000 litre = 50,000 g / 1,000,000 ml[(cm3)] Gcllau (talk) 05:30, 9 April 2008 (UTC)

for clarification what do you mean here? 50 kg per cubic metre is 50 kgm-3 im not sure but i think you might be mixing you units and without checking my maths (will do a bit later when i have time,  i think you are refering to 0.05 kgdm3 or kg per decimetre which is a rather non-standard unit, correct me if im wrong but thats what i think you are saying  (50 kgm-3 is equivalent to 0.05 kgdm3 also 0.00005 kgcm3 )

oh and hello (Firebladed (talk) 12:03, 16 April 2008 (UTC))

Can gases sink?
If you had a high-density gas, such as Radon, and a low-density solid, such as lithium, in the same container, would the solid (lithium) float on top of the gas (radon)?

Madking 06:02, 14 September 2007 (UTC)

Density is density, more dense sinks below less dense. Which is denser, your radon or your litium? DMacks 16:26, 14 September 2007 (UTC)

What is it?
DENSITY IS MASS TIMES VOLUME I THINK IM PROLLY WRONG —Preceding unsigned comment added by 72.229.202.43 (talk) 00:56, 24 October 2007 (UTC)

Yup, you're wrong. As the article states several different ways, it's mass divided by volume. DMacks 01:13, 24 October 2007 (UTC)

Vandalism
This article was subject to a high number of vandalism attempts recently. It may be good to block it for unregistered users.--Afluegel (talk) 19:11, 22 December 2007 (UTC)
 * Thanks for the article protection.--Afluegel (talk) 20:18, 22 December 2007 (UTC)

density
what is density? Density is how much stuff is put in an object. —Preceding unsigned comment added by 76.224.99.236 (talk) 23:22, 13 January 2008 (UTC)

density= mass\volume. —Preceding unsigned comment added by 218.248.5.199 (talk) 06:27, 11 November 2008 (UTC)

Merge Common rock densities
I have proposed a merge into this article. Comments? Oppositions? Pro bug catcher (talk • contribs). 14:50, 8 April 2008 (UTC)
 * It's uncited, so the data itself is suspicious. Also, it's not really useful info at all IMO...seems like readers would know the rock and want to find its density (i.e., look at the specific rock's own page first), rather than a list of a few rocks' density values together (list probably is not comprehensive enough for specimen identification). I'd say just scrap it entirely. DMacks (talk) 15:02, 8 April 2008 (UTC)
 * I agree, but haven't found anything in the deletion policy on articles like that (listcruft, unrefereced, not useful, etc.) Pro bug catcher (talk • contribs). 12:24, 9 April 2008 (UTC)
 * I PRODded the page, so unless someone objects, it'll become deletable in a week or so. DMacks (talk) 21:28, 16 April 2008 (UTC)

"Various substances have different densities, and it is this quantity that determines how they interact when mixed together."

this line is misleading. Miscibility, charge, etc., determines mixing behavior. Density determines buoyancy

Suggested restructure (rewrite?)
The opening statement starts the confusion "the density of a body" suggests only solids! I know we talk of a "body of water", but a body of gas? This article should be clearly divided into "Density of solids" (then you can mention thermal expansion, how to measure it, and some interesting examples), "Density of Liquids" (again, you can go into temperature effects, how to measure it, and some interesting examples) and Density of gases (temperature and pressure effects, how to measure it, and some interesting examples). Water is not a particularly interesting special case... no need for its own section.

Other gripes... please don't use the about.com "density affects...behave... when mixed together". Crude at best, misleading at worst (suggests some sort of chemistry going on". Just link to buoyancy.  "Density is the ratio of mass to volume"... sort of.  Here, about.com has it better.  Density is actually mass per unit volume.  Subtle, but important.  Add if you like... "in layman's terms, density is a measure of how much substance is present or contained in a given volume of space."  Even if the Archimedes story is apocryphal, precise measurements would have been possible even in his day.  There exists a device, albeit an archaic one, called a "Eureka can".  Filled to the brim with water, full immersion of a solid cause water to overflow, down a spout and into a receiver.  Imagine Archimedes displacing water by the crown onto one side of a balance, and water from his pure gold reference (of identical mass to the crown) onto the other side.  If the balance is "unbalanced", the gold and crown were not of the same substance! Simple and sensitive. 75.144.215.110 (talk) 16:31, 5 August 2008 (UTC)

units
I know wikipedia is run, operated, edited and most often used by the whining, marxist "Blame America First" crowd, but America is still the country that put man on the moon 6 #$%#ing times and as an engineer living in America, a separate table of USCS units would be extremely helpful!!! —Preceding unsigned comment added by 67.160.181.158 (talk) 04:27, 5 October 2008 (UTC)
 * Well, there is no reason you can't do it yourself, unless you wish to stereotype, you lazy american. What are the standard units of density in the US? Noodle snacks (talk) 09:23, 22 October 2008 (UTC)

addexternallink
i wanna add my external link, http://petrochemical.gronerth.com/linkus.php?link=1101, relative a density of hydrocarbons, however, i want to know if can add it?, because, my last link, about the compute of density of hydrocarbons was deleted. —Preceding unsigned comment added by 190.136.29.16 (talk) 20:35, 7 November 2008 (UTC)

Black hole
The entry in the material column should read specifically "earth-mass black hole", if it really makes sense to to talk about density in the context of black holes at all. (A black hole's mass is directly proportional to its radius, not its volume. I.e. if you squish two black holes together, the resulting hole will have a diameter that is roughly the sum of the two original holes' diameters--rather different behaviour than one would expect from a material object. Consequently, a large hole's "density" is much less than that of a small hole, in proportion to r^2.)  —Preceding unsigned comment added by 99.225.147.4 (talk) 23:00, 14 December 2008 (UTC)

Density; both in theory and practice
The atom with its electron cloud and tiny nucleus is mostly empty space. The ratio of size of whole atom to its nucleus is 1/10000. Since mass of one proton/neutron is 1836 times heavier than electron. So the ratio would still be same even if we add a mass of one proton to nucleus for the compensation of all electrons of element of highest electronic configuration. Ignore the packing factor/ compressing of nucleus in order to make it more dense.

Density of an atom = Mass /volume.

Density= mass of all proton, neutron and one extra proton which was added for the compensation of electrons/ volume of whole atom

The figure is too small as 99.0009% volume of the atom is empty.

Now with the help of Avogadro’s numbers we can calculate the number of atoms in a mass of 1 kg of any element say aluminum. So theoretical density of 1 kg of Al will be 0.0001% of its real desity as 99.0009% theoritical volume of 1 kg of mass is empty. Also, theoritically we can squeez steel or other hard material becuase of aforementioned ratio.

But in reality, a mass of one kg of steel / iron or other hard material is composed of 99.0009% solid mass and rest empty and may be less than this and hard to squeez. 96.52.178.55 (talk) 20:17, 17 May 2009 (UTC) Khattak

Here is the Yahoo team answer " http://ca.answers.yahoo.com/question/index;_ylt=Ai6rdU3CljVL4qZvefjJMInAFQx.;_ylv=3?qid=20090516025238AAoeM3W" Don't know but use your own common sense about the ratio 1/10000.

Assessment comment
Substituted at 08:54, 19 April 2016 (UTC)