Talk:Density

Add reference or example

"Osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser." Which compounds are denser than Os or Ir? Or are we talking about non standard conditions? — Preceding unsigned comment added by 200.232.235.231 (talk) 05:24, 14 June 2019 (UTC)

Add to table: High density liquids at room temperature

Methylene Iodide is unique in that it is a dense (3.325 g·cm−3) room temperature liquid and also an organic compound. It is useful in chemistry laboratories as a methylenating agent and for rare metal / diamond testing & refining liquid.

There is also Clerici solution (thallium formate plus thallium malonate in water). It is liquid at room temperature, with a density of 4.25 g/cm3, however this increases to 5 when warmed. It, along with methylene iodide, are useful for prospecting as they tend to cause precious metals to sink away from ore particles. With Clerici solution, the opposite occurs and diamonds float on it's surface. Another key to their usefulness in this application is that they do not form alloys or react with the items being refined, as gallium might.

Gallium's solid density is 5.91 g·cm−3 but it's melting point is just 29.76 Celsius. (Where it's density becomes 6.095 g·cm−3).

Various gallium alloys exist that are liquid at room temperature and below, e.g. Galinstan. Melting point, -19 Celsius. Density, 6.44 g/cm3 at STP. This has possible applications as a coolant and it, with gallium it's self, are of interest to electronics and semiconductor manufacturers.

Bromine is another example, at 3.1028 g·cm−3 and boiling at 58.8 °C 137.84 fahrenheit 331.9 kelvin

I believe these would make interesting additions to the table as they all have useful properties based on them being dense liquids at, or near, room temperature. A check of google for 'densest liquid' quickly highlights the number of people asking the same thing; with the sole response commonly being 'mercury'. Those examples sweep a good selection of different forms (e.g. none metallic element, metal, metal alloy, organic compound, solution).

No title

"...but not the densest materials." What are the densest materials ? What is denser than osmium ? — Preceding unsigned comment added by 165.222.184.132 (talk) 12:14, 13 October 2011 (UTC)

Not sure where to ask this, so I'll just put it here. On the table for #Densities_of_various_materials, could this be cleaned up, so it can be properly sorted by density? i.e. Removing intangible things or putting them in a separate table. Such as the Sun, core of the Earth, black hole, etc.. Thanks.209.150.195.106 (talk) 22:59, 10 November 2011 (UTC)

I was thinking the same thing. Working on that now! Dudecon (talk) 23:50, 13 February 2012 (UTC)

What a terrible idea!!! You messed up the whole table. Now it's very difficult to read and compare. It's called SCIENTIFIC notation for a reason!

Reviewing Cheatsheet

The following highlights current issues. Feel free to either add the issues you've identified, or to strike them as they've been resolved.

See also: Wikipedia:Featured article criteria and Wikipedia:Featured list criteria

WikiProject Physics' Reviewing Cheatsheet (11:16, 8 July 2008 (UTC))

Do not remove the elements, but rather strike them as they becomes useless or irrelevant (i.e write <s>text to be struck</s>) to indicate that this element was verified and found to be alright.
If everything in one of the section (i.e everything in one hidden-box has been addressed), strike that particular hidden box's title.
This cheetsheet can be used by anyone.
To add the Reviewing Cheatsheet to an article's talk page, simply place {{subst:Wikipedia:WikiProject Physics/Projects of the Week/Reviewing Cheatsheet}} immediately before the first section.

Add/Expand !

• Add/Expand :

• The following sections needs to be expanded/created :

• Lead
• Overview !
• References
• Lists ?
• See also

• Infoboxes and Navboxes :

• The following navboxes and infoboxes could be useful :

• WikiProject Physics templates (browse)
• Physics navboxes (browse)
• {{Nobel Prize in Physics}}
• {{Infobox Scientist}}
• {{Infobox Particle}}

Categorize

• Categorize

• Make sure the article is properly categorized :

• Browse Category:Physics, to find other categories
• Do not overcategorize
• Categorize alphabetically

Cleanup?

• Cleanup

• Article MoS Compliance :

• Acronyms and abbreviations are spelled out on first use
• Appropriate use of reference templates
• En dashes, em dashes, hyphens, and minus signs are properly used
• External Links
• Images/Diagrams

• Captionned
• Correctly aligned

• Layout
• Lead
• MoS (biography) compliance
• MoS (dates and numbers) compliance
• MoS (mathematics) compliance
• Overlink
• See also

• Copyediting :

• The following sections needs to be copyedited (give reason) :

Copyright?

• Copyright :

• The following elements are copyrighted and are not fair use.

Disambiguation!

• Disambiguation :

• The following elements needs to be disambiguated :

• mass density vs weight density

• Considering referring these section to a main article :

• The following elements may be too technical for the casual reader, consider defining and explaining them to non-experts:

Merge/Split!

• Merge/Split :

• Consider merging or splitting these sections with another article, or merging another article's section with this one (give reason):

• densities of water needs to be split off (too specific for general article)
• density of air already exist (split of most of density of air section and merge) include main

Problems

• Problems :

• The following problems have been identified :

• Neutrality is compromised
• Minority views are given too much exposure
• Weasel words and peacock terms
• Editorial feel
• Use of other Wikipedia articles as references
• Trivia sections

Requests

• Requests :

• Consider making a request to these people (give reason):

Talk page

• Talk Page :

• Archive old and irrelevant discussions
• Consider structuring discussion according to "topics"
• Sort boxes in this order (consider adding them if they aren't there):

• {{skiptotoctalk}}
• {{talkheader}}
• {{ArticleHistory}}
• Wikiprojects (browse to find other relevant projects)

• If there are more than one WikiProject, use {{WikiProjectBanners}} and order them alphabetically within the banner.

• WP 0.5/1.0 Editorial Team,
• WP Echo
• Other boxes
• To do box
• Archive box

• Update importance and rating

Update

• Update :

• These sections or statements are out of date :

Verify

• Verify :

• The following needs to be verified :

• Factual accuracy
• References
• Name of the article
• Up-to-date-ness

Wikilinks

• Wikilink :

• The following elements needs to be wikilinked :

• People
• Experiments
• First use of units
• Dates (but not stand alone years)

Miscellaneous remarks

• Miscellaneous remarks :

Oddly, while properly coded, the symbol for rho is improper in the definition following the equation (in which rho shows properly (Firefox/Mac OS X). —Preceding unsigned comment added by Alanbrowne (talk • contribs) 15:59, 17 May 2010 (UTC)

Cheatsheet last updated by: (TStein (talk) 05:19, 12 July 2008 (UTC))

Gravity is a special case of Density with two objects or more

may be, Gravity is a special case of Density the electron does not spin fast enough to merge with the nuclei of the atom, i.e. lower mass/vacuum energy momentum torque of electron to that of the nuclei of the atom, may be because of the electron's smaller mass radius in comparison to the atom's larger radius. when moving to a higher vacuum energy density (may be because larger mass of the nuclei accumulate larger vacuum energy vector near or on it's surface with it's own torque momentum with vacuum energy)near the nuclei of the atom: electron loses photon because it must spin faster (higher torque momentum of the electron's matter surface resistance vector and the vacuum energy vector which leads to a higher spin of the electron),noting: lower energy vacuum space energy with higher energy matter of the electron and/or the nuclei of the atom. density= matter/vacuum energy--99.109.130.141 (talk) 03:54, 7 October 2010 (UTC)--e:Y,?:G 03:55, 7 October 2010 (UTC) I have initiated this discussion about Density because I have not read an article (or I could not find one) where the topic is: Density of matter in vacuum or Density of matter with respect to vacuum energy, which is very important to physics.--e:Y,?:G 04:15, 7 October 2010 (UTC) —Preceding unsigned comment added by E:Y,?:G (talk • contribs) in other words, could it be that: if and where matter is inside vacuum i.e. vacuum energy and at vacuum large enough in volume, density = matter/vacuum energy is higher,denser energy medium i.e. matter/lower,lesser energy medium i.e. vacuum energy

then

the lower, lesser energy medium i.e. vacuum energy would want to "dilute" the higher, denser energy medium i.e. matter; therefore, the inward force exerted by lower, lesser energy medium i.e. vacuum energy onto the higher, denser matter.--e:Y,?:G 04:47, 7 October 2010 (UTC) —Preceding unsigned comment added by E:Y,?:G (talk • contribs)

Density of a black hole

I it may be a stupid question but isn't the density of a black hole infinite? I mean isn't that kind of how a black hole is defined, as a point in space with no extent, a specific mass and infinite density. and that is why light can't escape.

No. The "singularity" at the center of a black hole might be a point in space with no extent, but there's no way to tell, because if you're closer than a specific distance from the center, even light (or radio signals) pointed straight away from it can't get away. This distance, called the Schwarzschild_radius, defines the sphere surrounding the singularity, called the "event horizon", from within which light cannot escape.

Interestingly, all black holes rotate, and the rotation deforms the black hole's event horizon. I don't know if this alters the enclosed volume or not... a better physicist than I will have to answer that one. Dudecon (talk) 04:46, 2 August 2014 (UTC)

You can take the mass of a black hole, and divide by the volume of this sphere, to get a value with units of density. If you take a black-hole and double its mass by throwing in more matter, its radius will also double -- so interestingly, the more massive a black hole is, the less dense it is.

Example: If you took the Earth (6×10²⁴kg) and compressed it to a "point in space with no extent", the closest you could get to that "point" and still radio out would be 9mm. That's a peanut-sized volume 3cm³ in size, for a "density" of 2×10³⁰kg/m³.

On the other hand, the super-massive-black-hole at the center of the Milky Way Galaxy is around (9×10³⁶kg), one and a half trillion times more massive. Its radius (13.5 million km) is larger by the same factor, for a "density" of 9×10⁵kg/m³. That's still denser than "the core of the Sun", but way lower than an Earth-mass black hole. (User not logged in) 03:32, 8 March 2013 (PST)

....

You know, given that a black hole's density drops as its mass increases, it's incorrect and misleading that the article lists black holes as having the single, inconceivably-huge density of 2×10³⁰kg/m³. An Earth-mass black hole is impossible primarily because there's no known force capable of compressing material to such a density. Given that they're impossible, perhaps their density doesn't belong in the article.

The least massive black holes that actually exist are several times the mass of the Sun, and this (higher) mass corresponds to a (lower) density, comparable to the density at the core of a neutron star, (1×10¹⁸kg/m³ according to this article), making that pretty much the highest density possible. From that point on, the more mass you pour into the black hole, the less dense it gets. — Preceding unsigned comment added by 76.77.184.22 (talk) 09:25, 6 April 2013 (UTC) I changed the table so now it gives densities for stellar-mass and supermassive black-holes (which exist), rather than Earth-mass black holes (which don't).

Perfect. I like the way the article deals with black holes now. Specific example masses with specific densities. Well done! Dudecon (talk) 04:46, 2 August 2014 (UTC)

If it doesn't have infinite density, then some amount of radiation can escape and then it's not a black body.Rphb (talk) 21:17, 23 June 2012 (UTC)

All that is required for a black hole is a gravitational gradient with an escape velocity which exceeds the speed of light. A body doesn't have to be anywhere near infinite density to achieve this. Singularities have never been observed, and may very well not exist. Dudecon (talk) 04:46, 2 August 2014 (UTC)

Should we also include the most massive currently known SMBH - S5 0014+81 in this list? Would be informative, according to me. More so in view of the discussion above, concerning the mass-density relation. Since its mass is estimated at 4×10¹⁰M_☉, while another study suggests a 10 times lower estimate (due to an effect of amplification of the jets' brightness), we could pick any of the runner-ups instead: List of most massive black holes.--Bobbylon (talk) 00:19, 10 November 2016 (UTC)

Density of nonideal solutions

Measurements of densities of solutions/mixtures can be used to determine activity coefficients. This statement has been labeled as unsourced.--193.231.20.25 (talk) 10:11, 14 January 2014 (UTC)

There is no real need to be sourced.--193.231.20.25 (talk) 13:30, 15 May 2014 (UTC)

I see no equations or qualitative relationships given (the term "activity" doesn't even appear in this article), nor is there anything in activity coefficient explaining specifically how that parameter directly mathematically affects density. DMacks (talk) 22:48, 15 May 2014 (UTC)

The activity coefficient has some formula linking excess volume and enthalpy to activity coefficient. It is known that these excess quantities are equal to the volume and enthalpy of mixing having non-zero values in non-ideal solutions where also the activity coefficient differs from unity. Of course some equations must be inserted to provide context for the statement discussed here.--188.26.22.131 (talk) 10:03, 19 May 2014 (UTC)

In this relation which express density as a function of the densities of pure components of the mixture and their volume participation in mixtures with no interaction between the components:

$\rho =\sum _{i}\rho _{i}{\frac {V_{i}}{V}}.\,$

necessary substitutions could be made.--188.26.22.131 (talk) 10:15, 19 May 2014 (UTC)

like $V=\sum _{i}V_{i}+\sum _{i}V_{i}^{E}$--193.231.20.25 (talk) 11:26, 20 May 2014 (UTC)

What is the relationship between Denstiy and Scratch resistance?

What is the relationship between Denstiy and Scratch resistance? — Preceding unsigned comment added by 193.194.132.70 (talk) 12:04, 1 August 2014 (UTC)

Scratch resistance has more to do with hardness and elasticity than with density. There is probably some correlation between low density and low hardness, but high density is no guarantee of hardness or scratch resistance. For instance, Gold is very dense, but scratches easily because it is soft and inelastic. Tungsten Carbide is dense, but also very hard and is highly resistant to scratching. Rubber is not hard, but very elastic, and because nearly all of the deformation is non-permanent, it is hard to scratch. Dudecon (talk) 04:31, 2 August 2014 (UTC)

Semi-protected edit request on 4 January 2015

Correct the units in the table "Densities of various materials covering a range of values". It is support g/cm^3, not kg/m^3. Maxralf (talk) 16:59, 4 January 2015 (UTC)

 Not done as the existing units are correct - e.g. water weighs 1,000kg (1 Tonne) per cubic metre, it does not weigh 1,000g (1 kg) per CC. - Arjayay (talk) 17:19, 4 January 2015 (UTC)

Edit Request: "Common Units" Should Show Actual Density Terms

The subsection for U.S. Customary Units under the Common Units heading makes conflicting statements. It includes both lb/ft^3 and slugs/ft^3 as possible density units. This is physically incorrect, as noted in another section, as lb/ft^3 is a term for unit weight. Slugs/ft^3 is the only correct term in the set.

If the common usage of lb/ft^3 in place of density is to be noted, that should be NOTED in the units section so that a person does not conclude that weight/volume is the proper way to calculate density, as we know that mass/volume is the definition of density.

Please make this edit. Thank you. — Preceding unsigned comment added by 129.252.33.12 (talk) 21:42, 25 January 2015 (UTC)

The mass versus weight confusion is common for the unit of "pound". Our Pound (mass) article seems pretty explicit that "lb" is a standard unit of mass (correlates with kilogram), whereas the Pound (force) defines based on it (the force of the mass at earth's gravity); the force sense is not the fundamental unit. Note that the first time the term is used as a US unit, it's called (and linked) explicitly as "Avoirdupois pound", which is by definition specifically the mass-unit not the force-unit. DMacks (talk) 04:06, 26 January 2015 (UTC)

Semi-protected edit request on 10 February 2015

The table of approximate material densities needs to be corrected. The density units in the header are in kg/m^3 so that air is shown correctly at 1.2kg/m^3. What is then incorrect is to show water as 1kg/m^3 and I suspect a lot more of the solid materials in the table also need to be increased by 1000. These figures have probably been taken from another table with units of g/cm^3. For instance Gold is shown as 7.? whereas I'd expect a cubic metre of gold to be many tonnes - probably 7000 kg or so and water, not 1.0 but 1000 as it shows in an earlier table. 86.190.18.53 (talk) 17:58, 10 February 2015 (UTC)

 Not done I cannot see a "Table of approximate material densities" but assuming you mean the "Various materials" table, Water does not say 1kg/m³, it says 1,000kg/m³ that is a comma not a stop. As for the Gold figure, I can only see 19,320 not 7.? - Arjayay (talk) 18:14, 10 February 2015 (UTC)

External links modified

Hello fellow Wikipedians,

I have just added archive links to one external link on Density. Please take a moment to review my edit. If necessary, add {{cbignore}} after the link to keep me from modifying it. Alternatively, you can add {{nobots|deny=InternetArchiveBot}} to keep me off the page altogether. I made the following changes:

• Added archive https://web.archive.org/20100805010226/http://oilgasglossary.com:80/density.html to http://oilgasglossary.com/density.html

When you have finished reviewing my changes, please set the checked parameter below to true to let others know.

This message was posted before February 2018. After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than regular verification using the archive tool instructions below. Editors have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the RfC before doing mass systematic removals. This message is updated dynamically through the template {{source check}} (last update: 5 June 2024).

• If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
• If you found an error with any archives or the URLs themselves, you can fix them with this tool.

Cheers. —^{cyberbot II}_{Talk to my owner:Online} 22:59, 25 August 2015 (UTC)

Semi-protected edit request on 23 September 2015

206.80.31.55 (talk) 19:41, 23 September 2015 (UTC)

Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format. Cannolis (talk) 19:45, 23 September 2015 (UTC)

Semi-protected edit request on 11 November 2015

Please fix sorting of table "Others" so that Interstellar medium (kg/m³ = 10^-19) is correctly sorted as smaller than the other elements of the list Wheatbyproducts (talk) 04:31, 11 November 2015 (UTC)

• Done Thank you. --Stabila711 (talk) 04:04, 18 November 2015 (UTC)

a question

When we say that density is a positive scalar quantity. What do we actually mean by positive here ? --Ankit2299 (talk) 06:58, 31 December 2015 (UTC)

Possibly "not less than zero"? That follows logically from its definition based on mass and volume, neither of which seem like they could be negative values. DMacks (talk) 07:12, 31 December 2015 (UTC)

Semi-protected edit request on 1 December 2016

195.171.207.74 (talk) 13:06, 1 December 2016 (UTC)

jkfjjfrkmfrekj,fngkfdmvfkdhkfkfkkfkfkkf §§§§§§§§§§§§

Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format. Sunmist (talk) 13:32, 1 December 2016 (UTC)

Semi-protected edit request on 24 February 2017

I'd like to update the value for density of seawater. There is a standard value at 25C and 35 g/kg salinity. The current value is way off. I'd like to update it to 1023.6 kg/m3, referring to the website: http://web.mit.edu/seawater/ and the papers: a. K.G. Nayar, M.H. Sharqawy, L.D. Banchik, and J.H. Lienhard V, "Thermophysical properties of seawater: A review and new correlations that include pressure dependence," Desalination, Vol. 390, pp.1-24, 2016. doi:10.1016/j.desal.2016.02.024 (preprint) b. Mostafa H. Sharqawy, John H. Lienhard V, and Syed M. Zubair, "Thermophysical properties of seawater: A review of existing correlations and data," Desalination and Water Treatment, Vol. 16, pp.354-380, April 2010. (PDF file which includes corrections through January 2016.) Betterworld123 (talk) 22:47, 24 February 2017 (UTC)

Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format. -- Dane ^talk 21:55, 3 March 2017 (UTC)

Concrete

Value given in table for concrete is 2,000 kg/m3, but all other sources I have read, including Wikipedia page "Properties of Concrete", give a typical value of 2,400. Please can someone review and edit as necessary. — Preceding unsigned comment added by 42.98.92.235 (talk) 06:32, 9 May 2017 (UTC)

Yes, that is sourced in the lede of [concrete]]. Will adjust. - DePiep (talk) 19:16, 9 February 2018 (UTC)

Planck Density

Planck density: density of hypothetical Planck Star or central object of black hole present there instead of singularity. 2601:580:109:FFAD:DD87:4ADD:F44:264E (talk) 01:08, 12 February 2019 (UTC)

References

What is the significance of density and sp gr. test in oil industry field?

What is the significance of density and sp gr. test in oil industry field? 185.240.17.40 (talk) 07:27, 29 March 2022 (UTC)

"Osmium and iridium are the densest known elements at standard conditions for temperature and pressure"

• Osmium: 22.61g/cm³. [1]
• Iridium: 22.65g/cm³ [2]
• Hassium: 41g/cm³ [3]

Do we only include stable elements? Hassium is unstable with isotope-276 having the longest half-life of 1.1 hour.[4] Plutonium is unstable with isotope-244 having the longest half-life of 80.8 million years. Do we include plutonium? 2600:1700:D0A0:21B0:16C:429D:E228:58EB (talk) 01:02, 16 May 2022 (UTC)

My guess is that only includes experimentally measured densities. We don't really know enough of hassium's crystal structure. 74.135.194.87 (talk) 18:24, 17 February 2024 (UTC)

Orders of magnitude (density)

Who got rid of the page (Orders of magnitude (density) )? 74.135.194.87 (talk) 18:25, 17 February 2024 (UTC)

Iit

The ratio of density of two substance a and b is 3:1 and the relative density of object be is 4 the density of substance a is 117.246.17.26 (talk) 01:17, 21 August 2024 (UTC)

Whew.

It may be worthwhile to separate the concept of density of 1. Normal matter at every-day pressures 2. Density of matter at extreme pressures (Earth's core, Sun's core, Neutron stars) and 3. Density as part of the General Relativistic Conservation Law (i.e Conservation of Mass-Energy-Stress aka Mass-Energy-Density).

The other thing I want to comment on is the existence of material (at STP...although perhaps we should say "at 1-g and STP"?) that is denser than Osmium. I suspect, but can not document, it *does* exist. For instance, Os "readily absorbs hydrogen". So, it's likely that it does so with little volume change, but with increased mass (hence increased density). It's well known that for sufficiently large atoms, small atoms (like H) can exist interstitially (in the spaces between the large atoms) with minor changes in volume. I did a quick online search and couldn't find any density information of the (density) phase diagram of Os-H. The stuff would be very difficult to work with, not to mention expensive, but perhaps someone has a nugget of pure Os and would be willing to let it soak up some H2 and measure it's weight over time. One can hope.98.17.180.146 (talk) 13:35, 14 October 2024 (UTC)