57 votes
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Why isn't the American nickel magnetic?

There are many types of magnetic properties, including ferromagnetism, paramagnetism, diamagnetism, antiferromagnetism, ferrimagnetism, superparamagnetism, metamagnetism, spin glasses, and ...
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34 votes

Why does mercury decolourise a gold ring?

The grey colour is an amalgam of mercury and gold. Mercury forms amalgams with many other metals. Some are used as chemical reagents in laboratory chemistry as they have different properties than the ...
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33 votes

Is "stainless" a bulk or a surface property of stainless steel?

Let's divide the steel world into two classes: 1) rusting steel and 2) stainless steel. Rusting steel, in the presence of oxygen and moisture, will oxidize, forming hydrated iron oxides/hydroxides ...
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27 votes
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Will we ever run out of gold, silver, copper and other important conductors?

How long will these reserves last? Short answer: longer than you think and will outlast me, you, our children and our grandchildren. Possibly last forever. Long answer: This is a fairly complex ...
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  • 5,004
25 votes

Why isn't the American nickel magnetic?

None of the US coins are magnetic (ferromagnetic), except for the 1943 Lincoln penny (Steel Cents, made in steel and zinc to save copper for ammunition during wartime), which are considered magnetic. ...
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21 votes
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Is "stainless" a bulk or a surface property of stainless steel?

It is usually a bulk property though you would need to know exact regulations for your country to be certain. Stainless steel is steel (i.e. iron + a little bit of carbon) alloyed with another metal (...
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  • 2,874
20 votes

How do manufacturer remove oxygen from metal during melting?

They use flux, that's how. That is, an inert substance which melts easier than the metal and floats on top, preventing it from oxidation in the air. Common fluxes for aluminum seem to be based on ...
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15 votes

How can steel be so different from iron, even if amount of carbon is small?

One of the key considerations is that much of the interesting mechanical behaviour doesn't occur within the bulk of the material - it occurs at the interfaces between crystals (known as grains). Grain ...
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14 votes

How to separate Cu and Ni from alloy containing different metals such as Al, Cu, Ni, (Zn, Pb, Sn < 5%)?

First, the alloy $(0.5$ to $\pu{2 g})$ should be treated by $\pu{10 mL}$ nitric acid $32\,\%.$ All metals will get dissolved, except tin and silicon, which will be transformed into insoluble dioxide $\...
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13 votes
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What does it mean to 'fuse' ores and why do we use alkali metals in the process?

"To fuse" is another word for "to melt" (e.g. "heat of fusion"). Specifically, if you say you want to fuse two materials, you melt them in the hope that they will mix. In this case, you melt the ...
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12 votes
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Why are the sulfide ores generally converted to an oxide and then reduced?

Why, it's simple: you heat a metal oxide with carbon, and you get the metal you were after, plus a byproduct of $\ce{CO}$ or $\ce{CO2}$ which easily flies away. Coal is still abundant on our planet. ...
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11 votes

How does chromium help stainless steel prevent rusting?

TL;DR Note that the passive layer forms on the surface, there needn't be any change to lattice constant. Chromium needn't migrate , the Cr present on the surface will form the layer to protect it....
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  • 1,241
11 votes

Why does mercury decolourise a gold ring?

Once when I was doing a experiment I have this experience, my ring was decolourised. I was afraid first but we can reverse it to the gold again. There is no reaction between gold and $\ce{Hg}$ and it ...
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11 votes
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Leaching of copper using zinc

We can. But I see few reasons why it is not used: Iron is much cheaper than zinc. There can be remaining residue of iron/zinc, coated by copper, or just being excessive. While copper can be melted ...
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  • 28.6k
11 votes

Is "stainless" a bulk or a surface property of stainless steel?

"Stainless" is not a specific definition. The stainless steel with the least alloy is $5\% \; \ce{Cr}$ ( grade 501) according to AISI (It can't be cut with an oxygen/acetylene torch-like regular steel)...
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  • 3,193
10 votes

Which has more metallic character: aluminium or magnesium?

Two types of metallic character In fact, there are two type of metallic character if you look at the metal from the chemical point of view or if you look at the metal from the physical point of view: ...
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10 votes
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Obtaining 100% pure metal

The only way to get a "100% pure" sample of an element is by mass spectroscopy, or something similar, which acts on each atom (or ion, actually) one at a time. So you could get a sample of pure ...
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10 votes

What does it mean to 'fuse' ores and why do we use alkali metals in the process?

As a comment of Karl's message, I would like to add that chromite $\ce{FeCr_2O_4}$ is the most important Chromium mineral. When mixed with $8$ times its weight of sodium carbonate, and heated to high ...
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10 votes

Why is the only natural source of radium compounds uranium minerals?

You can't find primordial radium because it's half life is too small compared to earths age. Even the radium isotope with the longest half life, $\ce{^{226}Ra}$ has a half life of only 1600 years ...
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9 votes

What possibilities are there for refining aluminium on the moon?

My theory was to use electromagnetic separation, aka the Calutrons used in the Manhattan Project. Fine powder feedstock (check), into an arc discharge to vaporize and ionize (lots of good designs for ...
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  • 7,670
9 votes

Do there exist metals that are composed of molecules?

According to A Conducting Crystal Based on A Single-Component Paramagnetic Molecule, [Cu(dmdt)2] (dmdt ) Dimethyltetrathiafulvalenedithiolate) J. Am. Chem. Soc., 2002, 124 (34), pp 10002–10003 : ...
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9 votes

Why aren't soldering tips coated with platinum?

Sigh - as pointed out by @user83678 some 3+ years after first writing this, I answered for Pd, not Pt. That will teach me to pay attention. But, the general answer remains the same. There are enough ...
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  • 7,670
9 votes

Is "stainless" a bulk or a surface property of stainless steel?

Quick and simple: Steel = iron + carbon (less than 2%; also called "forgeable iron") Adding chromium (min. 12 %) makes it stainless. These chromium atoms are spread over the full volume of your block,...
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9 votes

How can steel be so different from iron, even if amount of carbon is small?

Let's consider that steel may contain $\pu{1\%}$ carbon. I know it is a bit much. Let us express this mass concentration as molar concentration for a sample of $\pu{100 g}$ of steel. Since this sample ...
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  • 21.8k
8 votes

Are there carbon-silicon alloys?

Here you can find a phase diagram for $\ce{Si/C}$ system. It does not have zones with homogeneous non-stohiometric solids. So, there is not thermodinamically stable Si/C isomorphic alloys. However, ...
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8 votes
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Why doesn't the Bessemer process oxidize the iron?

I thought you asked a great question, one that I have wondered about myself. The answer, as best I could determine, is that the iron does oxidize. A good description of the Basic Oxygen Steelmaking ...
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8 votes
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Do there exist metals that are composed of molecules?

Sort of, if you define metals as substances that exhibit some metallic behaviour Metallic elements are, well, the metals. But other substances can exhibit many of the properties of those metals. One ...
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8 votes

Reaction between alumina and aqueous sodium hydroxide, which one's right?

Quoting from chemguide (emphasis mine): With hot concentrated sodium hydroxide solution, aluminium oxide reacts to give a solution of sodium tetrahydroxoaluminate. $$\ce{Al2O3(s) + 2NaOH(aq) + ...
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  • 22.5k
8 votes

How do manufacturer remove oxygen from metal during melting?

There are two aspects to this, firstly is actually reducing the pure metal from its oxides, usually called smelting, most metal ores are metal oxides so this is clearly an important part of primary ...
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8 votes
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What happens to the carbon in carbon steel when it rusts?

Cast iron has considerable free carbon as graphite, but carbon steel has iron carbide in cementite, $\ce{Fe3C}$ in a ferrite ($\ce{α-F}$e) matrix, along with other phases and additives. In a corrosive ...
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