Wikipedia:Reference desk/Archives/Science/2019 June 28

= June 28 =

chemistry reference
Are all the physical and chemical properties of matter governed by its chemical composition? Suyogya1 (talk) 04:23, 28 June 2019 (UTC)


 * No. See for example Phase transition, Allotropy, and Microstructure.--Wikimedes (talk) 05:19, 28 June 2019 (UTC)


 * @Wikimedes by chemical composition i just not mean proportion of atoms only, but also their molecular structure, orientation, configuration, bonding type, bonding strength, etc. because for a particular proportion of atoms there exist these fixed properties. see The topics referred by you are just having those properties i.e., allotropy is structural modification, microstructure is highly magnified structure.Suyogya1 (talk) 07:23, 28 June 2019 (UTC)
 * Yes: its chemical composition govern the physical and chemical properties of matter;
 * No: other things than its chemical composition also govern the physical and chemical properties of matter. Temperature for instance. Or electronic state. Many other.
 * And, in science, it is important to define properly what you are talking about, and to use common definitions. You cannot stretch the definition of chemical composition so as to include, say, effect of temperature on the molecule. Chirality (chemistry) give you examples of molecule with the very same chemical composition, but different properties. Gem fr (talk) 08:27, 28 June 2019 (UTC)
 * Allotropy is, of course, a chemical change (oxygen and ozone are two different things). Microstructure also is plausibly chemical in nature -- two diamonds, each a single molecule, are different because they contain different numbers and arrangements of carbon atoms.  However, a group of microscopic diamonds could be stacked in different ways without changing their chemistry, so sometimes this could be non-chemical.  But yes, surely temperature and phase are counted as physical rather than chemical changes. Wnt (talk) 16:12, 28 June 2019 (UTC)
 * @Suyogya1, I was thinking you had meant more than just composition (the relative amounts of each element) in your question. If you expand the question to include all chemical interactions, then the range of properties determined by the interactions also expands, and Gem fr and Wnt have given some good answers.  Physical extensive properties are probably not considered to be determined by chemical interactions, and as Gem fr has said, other things can also affect properties.  For example the Flexural rigidity of an I-beam is different from the flexural rigidity of a cylinder, but regardless of these geometric effects, at room temperature and pressure the flexural rigidity of iron is going to be a lot higher than the flexural rigidity of oxygen.--Wikimedes (talk) 22:33, 28 June 2019 (UTC)

I'm trying to understand this from the Hybrid Synergy Drive Article
"High gear (equivalent): When cruising at high speed, the engine turns more slowly than the wheels but develops more torque than needed. MG2 then runs as a generator to remove the excess engine torque, producing power that is fed to MG1 acting as a motor to increase the wheel speed."

Surely the speed is a function of torque at the wheels (overcoming friction), and you will not be able to do anything with a generator->motor that you couldn't do by changing the gear ratio? -- Q Chris (talk) 09:23, 28 June 2019 (UTC)


 * According to the article "the torque/speed conversion uses an electric motor rather than a direct mechanical gear train connection". They say the goal is for the engine to run at a single "optimal speed" without having to vruuum-vruuum-vruum up the gears like a usual car accelerating, or having to suffer losses at a continuously variable transmission. Wnt (talk) 10:27, 28 June 2019 (UTC)
 * you will not be able to do anything with a generator->motor that you couldn't do by changing the gear ratio? - True, but the gear ratio usually changes by fixed increments - e.g. European cars have 5-6 gear ratios. Having (essentially) two motors in parallel allow you have any gear ratio in some range, so to speak, which can more than compensate for the losses in the mechanical power -> electricity -> mechanical power conversion (because you then optimize the torque/speed point for higher engine efficency). Tigraan Click here to contact me 10:32, 28 June 2019 (UTC)


 * "True, but the gear ratio usually changes by fixed increments - e.g. European cars have 5-6 gear ratios" - I can see that this might be the case to fill in the gaps between gears in nacrs with fixed ratios. The Hybrid Synergy Drive has a Continuously variable transmission though, so that shouldn't be necessary. -- Q Chris (talk) 10:37, 28 June 2019 (UTC)


 * I have just re-read the article and now understand. It is not a CVT but classed as one for regulatory purposes: "This is why Toyota describes HSD-equipped vehicles as having an e-CVT (electronic continuously variable transmission) when required to classify the transmission type for standards specification lists or regulatory purposes.". The combination of electric motor and planetary gears acts like a cvt. -- Q Chris (talk) 11:55, 28 June 2019 (UTC)


 * Glad you are sorted out, but it is a CVT, just not a mechanical one. The actual architecture, using a differential driven by an engine generator and an MG was proposed (and built, and tested) in the 70s. By Americans.Greglocock (talk) 00:09, 29 June 2019 (UTC)

Copper cementation
After copper ions have been removed from solution by depositing them on solid iron metal, how do you get the iron out of the copper to get pure copper? 182.0.150.151 (talk) 11:02, 28 June 2019 (UTC)


 * I don't know how it's done in a manufacturing process, but at home you could rust it away. That is, expose the iron to air and saltwater until it turns to iron oxide powder and breaks off. You would then want to polish the copper to remove any remaining rust, and any corrosion of the copper. SinisterLefty (talk) 15:01, 28 June 2019 (UTC)


 * You don't. If your goal was pure copper, you would have deposited them electrolytically onto copper cathodes, directly from the solution. If you have copper on iron as a mixture, you would then dissolve one of them, and if you wanted the copper to emerge pure, then it might be the copper that you dissolved. Andy Dingley (talk) 15:59, 28 June 2019 (UTC)
 * More in Copper extraction, Copper_extraction and included links Gem fr (talk) 17:08, 28 June 2019 (UTC)


 * Conceivably you could be trying to get a copper cast of an iron object. Why I don't know.  I think hydrochloric acid could be used to dissolve the inner iron without touching the copper cast, but I don't know that's really workable. Wnt (talk) 21:39, 28 June 2019 (UTC)
 * If you are a pro you know how to do it. If you are not, copper is sold in general stores at a price low enough, the copper you'll get this way is not worth the acid (despite it also being so cheap). But if for some reason I wanted to do that, I'll rather heat the thing, copper melting temperature is hundreds of K lower than that of iron and easily produced (with a blowtorch nowadays). Gem fr (talk) 06:53, 29 June 2019 (UTC)
 * Just to add to the chorus that home extraction of copper is not worth it, watch the YouTube chemist NileRed, who did a video on extracting pure gold from jewellery. When he extracted the gold, he also spent time and materials recovering silver from his extraction solutions, but didn't even bother with the copper, as the cost of materials meant it wasn't even worth it, so he just pitched them.  It can be done rather easily, however, much easier using hydrochloric acid and powdered zinc, if you really want to do it.  You'll need a large excess of HCl to react away any excess zinc, but you do get a nice, relatively clean copper dust in the end.  I do the experiment with my AP chemistry students, it's part of a standard series of reactions called "copper to copper" where you dissolved copper metal with nitric acid, then do a series of reactions to it that so turn successively difference colors, and the last step is to recover the original copper.  You can find the procedures online easily enough.  But the zinc/acid method is a much cleaner method than the plating process the OP is attempting.-- Jayron 32 12:45, 29 June 2019 (UTC)
 * Gold and silver (and to some extent platinum) are precious metals. This means those metals which have, since antiquity, been easily smelted. They also have the usual shininess and avoidance of corrosion, but mostly they were adopted as valuable so early on simply because they were the metals which were available. In places where native copper was available that had a similar veneration and of course native iron even more so (but that's extremely rare).
 * So it's just easy to smelt gold and silver into bullion form. When I do it, I just use a crucible loosely filled with coffee grounds (the nearest finely-powdered organic medium) and pop it into the gas forge for a bit. It's not even too fussy about the flame chemistry.
 * Copper's much harder. Harder to separate from iron by this route, and hard to smelt without burning off more than you're producing. But still, the bronze sword people (Neil Burridge) and the experimental archaeologists do it regularly. Similarly for tin.  Zinc though can't be done this way, hence why metallic zinc wasn't available in Europe until the mid-eighteenth century (WP's coverage is pretty inaccurate for this though). Andy Dingley (talk) 13:16, 29 June 2019 (UTC)


 * I could imagine a case where depositing copper on iron, then removing the iron, might make sense. Let's say there was a decorative iron mask that still looks decent from the front, but due to improper storage is almost rusted through from the back. If we assume it's of little value, in part due to this condition, then creating a copper version, in better shape, that could be displayed without requiring a coat of oil to prevent rusting, might be desirable. (Obviously if it was museum piece, they would want to preserve the original no matter what the condition.) SinisterLefty (talk) 13:04, 1 July 2019 (UTC)




 * But why would you remove the iron?
 * If you're looking at electroforming copper onto steel (and mostly onto a graphite-coated wax former) look at the water cooling jackets on the cylinders of many water-cooled aircraft engines of WWI. Andy Dingley (talk) 14:29, 1 July 2019 (UTC)


 * You'd remove the rusty iron, in my scenario, because it's heavy and unpleasant, leaving a trail of powdery chunks of iron behind. Rust also stinks. If they wanted to wear the mask for some type of event, then wearing it with rusty iron against their face would be a particularly bad idea (although copper could still give them green skin, so a lacquer coating, or some type of pads to offset the mask from the face, would also be a good idea). SinisterLefty (talk) 15:04, 1 July 2019 (UTC)

Lion
Please, our article does not appear to contain this information. What is the natural lifespan of an African lion. Thanks Anton 81.131.40.58 (talk) 12:52, 28 June 2019 (UTC)


 * According to : "Lions in zoos may live into their late teens or early 20s. In the wild, a lioness may live up to 16 years, but males rarely live past the age of 12." Incidentally, there are two subspecies of lions in Africa:


 * Panthera leo leo − includes the lion populations in West and northern parts of Central Africa.
 * Panthera leo melanochaita − includes lion populations in East and Southern African regions.


 * I don't know if there's a significant difference in lifespans. SinisterLefty (talk) 13:48, 28 June 2019 (UTC)


 * Note that LiOns have a much shorter lifespan. :-) SinisterLefty (talk) 14:50, 28 June 2019 (UTC)