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170 votes
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Why can I touch aluminum foil in the oven and not get burned?

You get burned because energy is transferred from the hot object to your hand until they are both at the same temperature. The more energy transferred, the more damage done to you. Aluminium, like ...
Martin Beckett's user avatar
140 votes
Accepted

If I pull a metal bar for long enough with a constant small force, will it eventually break?

Yes, the rod will ultimately break—barring any other failure mechanism that occurs first. (Depending on the material and conditions, you may need to wait a very, very long time, but your mentions of &...
Chemomechanics's user avatar
132 votes

Why do metals only glow red, yellow and white and not through the full range of the spectrum?

The physics of why the heated metal glows like a black body has already been thoroughly covered in the previous answers. However, in order to completely bridge the gap with the physiology of color ...
Edgar Bonet's user avatar
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126 votes

Why can I touch aluminum foil in the oven and not get burned?

While it's true that the difference in specific heat capacity is to your advantage, its effect is really dwarfed by the mass difference. Typical aluminium foil is 0.016 mm thick and weighs 0.043 kg/m²,...
Dmitry Grigoryev's user avatar
45 votes

Are there physical properties that can be used to differentiate stainless steel from copper in a home environment?

Take advantage of the large difference in thermal conductivity between copper and stainless steel (approximately $400$ and $16$ $\mathrm{Wm^{-1}K^{-1}}$ respectively). If you put one end of a metal ...
jkej's user avatar
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43 votes
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Why do metals have free electrons?

Without getting into the quantum mechanical details, here’s a cartoon depiction of what’s going on. The vertical axis represents energy. Like other answers have already pointed out, metals don’t have ...
Superfast Jellyfish's user avatar
40 votes

How can electric fields be used to detect cracks in metals?

Cracks and other flaws can be found in metal parts by scanning the surface of the part with a small electromagnetic coil, which induces a current flow in the metal part as if the coil and the part ...
niels nielsen's user avatar
39 votes

Why do metals only glow red, yellow and white and not through the full range of the spectrum?

When metals (or any materials) get very hot, they emit "black body radiation". It's a funny name, because even "non black" bodies emit this thermal radiation. There may be some (small) deviations from ...
Floris's user avatar
  • 119k
31 votes

Are there physical properties that can be used to differentiate stainless steel from copper in a home environment?

Why not density? At least for a quick check and as for the title question. You are dealing with about < 8 and 9 g per cubic cm, respectively for steel and copper. Not overly laborious and ...
Alchimista's user avatar
  • 1,729
29 votes

If I pull a metal bar for long enough with a constant small force, will it eventually break?

This paper describes scientific creep tests with some specific steel. In a low stress (but relatively high temperature) regime, they report creep of 200 micrometers per year, for a test specimen of ...
AnoE's user avatar
  • 2,658
26 votes

How is silver a better conductor than platinum?

The situation is a lot more complicated than you described. When calculating the conductance of a metal, you first need to evaluate the allowed energy states of electrons in the bulk material, which ...
noah's user avatar
  • 10.3k
23 votes

Why do metals only glow red, yellow and white and not through the full range of the spectrum?

When I refer to a colour, eg green, I an referring to a range of wavelength which on entering the eye are perceived to be a range of colours depending on the intensity of each of the wavelengths ...
Farcher's user avatar
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22 votes
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Platinum seems to have higher kinetic friction coef. than static - how is this possible?

If you check the references in the Wikipedia article you linked, you will see that the source for the kinetic is different from the source for the static coefficient of the metals your mention (...
Bill N's user avatar
  • 15.4k
18 votes

Can electrons absorb photons?

Bottom line up front: You don't get absorption phenomena with a single free electron. You need to look at a system such as an atom or a crystal, in which there are more complicated dynamics at play ...
Andrew's user avatar
  • 47.5k
17 votes

Are there physical properties that can be used to differentiate stainless steel from copper in a home environment?

What about Eddy currents? If you've got a pair of strong neodymium magnets (doesn't everyone?) - move the straw in between two magnets with their poles opposing. Copper/Aluminum will have a strong ...
user3772748's user avatar
17 votes
Accepted

Is the specular reflection on a polished gold sphere white or gold in colour?

Yes, specular reflection from polished gold is gold colored. Due to the interband transition in gold, green and blue light gets strongly absorbed, biasing the reflected spectrum toward yellow and red. ...
Gilbert's user avatar
  • 11.8k
16 votes

Are there physical properties that can be used to differentiate stainless steel from copper in a home environment?

To see if the straw is stainless steel with a copper-colored coating, you can carefully sand or file off a bit of material from the end of the straw and see whether or not it is copper-colored ...
niels nielsen's user avatar
16 votes
Accepted

Why do group II elements conduct?

Even when an isolated atom has a filled shell, the electron bands in a solid crystal may be partially filled. The reason is that bands that originate from different atomic orbitals may actually ...
Buzz's user avatar
  • 16k
13 votes

How is silver a better conductor than platinum?

It appears that none of the responses so far have addressed the real reason silver is a better conductor than platinum. The reason is electron scattering. The simplest model for conductivity in solid ...
Gilbert's user avatar
  • 11.8k
13 votes
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Why can't the charge carriers leave the conductor?

Fundamentally they can't leave because they are attracted to the fixed positively charged atomic nuclei in the material. This results in the work function, meaning an amount of energy required to free ...
The Photon's user avatar
12 votes

Why do metals only glow red, yellow and white and not through the full range of the spectrum?

All wavelengths are included in what you call "white", thus all wavelengths are there. The evolution you are describing is the evolution of the black body radiation as heat is increased. You can ...
anna v's user avatar
  • 233k
12 votes

How is silver a better conductor than platinum?

I'll add my two cents to the other answers from the audio perspective that hopefully would clarify the "platinum cable" issue. First of all, there is a belief in the audio field that an ideal ...
safesphere's user avatar
  • 12.6k
12 votes

Can you make a metal denser by melting it and make it cool down under high pressure?

First of all, high pressure (i.e., compressive equitriaxial stress) is simply not going to induce cracks (or failure of any sort) in a uniform solid—there's just nowhere for the material to move to ...
Chemomechanics's user avatar
11 votes
Accepted

Why the electrons below the Fermi level do not conduct electricity?

Electrons in Solids Electrons in solids are treated by the so-called Band Theory, a quantum mechanical model for fermions interacting with a fixed crystal lattice. The solution to the Schrodinger's ...
Diracology's user avatar
  • 17.7k
11 votes
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Why are metals malleable and ductile?

Let's draw a comparison with ceramics, which—just as metals are generally ductile—are generally brittle. First, note that crystals (and metals and ceramics are both generally polycrystalline) can ...
Chemomechanics's user avatar
11 votes

Why can I touch aluminum foil in the oven and not get burned?

What's in discussion here is specific heat capacity. The flow of heat is based around temperature, and whilst that may seem like a fairly obvious statement, there are important distinctions to be made ...
DoublyNegative's user avatar
11 votes

Why can I touch aluminum foil in the oven and not get burned?

There are three categories of heat transfers: Convection and radiation transfers happen over the whole area (both sides!) of the aluminum foil while the conduction only happens over the area touched ...
Eric Duminil's user avatar
  • 1,897
11 votes

If I pull a metal bar for long enough with a constant small force, will it eventually break?

Under normal conditions structure building materials, such as steel, will not yield or break. Which is good, because all modern buildings and bridges are based on steel, even if embedded in the ...
Claudio Saspinski's user avatar
10 votes

Are there published predictions that hydrogen could remain metallic at ambient pressure?

According to http://iopscience.iop.org/article/10.1088/1742-6596/215/1/012194/pdf, "Brovman, Kagan, and Kholas[5] showed that hydrogen would be a metastable metal with a potential barrier of ~1 ...
akhmeteli's user avatar
  • 26.8k
9 votes

If I pull a metal bar for long enough with a constant small force, will it eventually break?

What matters here much more than force is stress: $$\sigma=\frac{F}{A_0}$$ where $F$ is the force applied to a bar with cross-section $A_0$. and the strain: $$\varepsilon=\frac{L-L_0}{L_0}$$ The ...
Gert's user avatar
  • 35.3k

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