# Tag Info

97

Toothpaste is what is called a non-newtonian fluid, more specifically toothpaste is a Bingham plastic. This means that the viscosity of the fluid is linearly dependent on the shear stress, but with an offset called the yield stress (see figure below). This yield stress is what makes it hard to say whether it is liquid or solid. The fact that toothpaste is ...

78

Hardness and toughness are not the same Hardness and toughness are very different qualities in materials and are weakly related. Hardness is strongly related to the more well-defined quantity of stiffness which measures how easily a compound can be deformed under stress. Glass and diamond are very stiff materials, for example. If you try to poke them with ...

41

The potassium is not added first because the potassium does not intrinsically make stronger glass, it is the substitution of a larger ion for a smaller one that does. To understand why ion exchange strengthens glass, you have to understand why the ion exchange makes the glass harder. The process of ion exchange hardening is done at a temperature that allows ...

40

Here's a genchem-level answer for a genchem-level question about the classification of matter: Toothpaste is a sol: a stable suspension of tiny solid particles in a liquid. When the toothpaste dries out you can see what the solid part alone looks like. Mixtures with more than one phase often have interesting properties and behaviors that the components ...

25

Diamond is one of the best thermal conductors known, in fact diamond is a better thermal conductor than many metals (thermal conductivity (W/m-K): aluminum=237, copper=401, diamond=895). The carbon atoms in diamond are $\ce{sp^3}$ hybridized and every carbon is bonded to 4 other carbon atoms located at the vertices of a tetrahedron. Hence the bonding in ...

25

Chemically-strengthened glass is similar tempered glass in that the outside of the glass is under compression, while the inside is not compressed. If all the sodium in chemically-strengthened glass were to be replaced by potassium, there would be no difference in stress between the interior and the exterior layer. How does this difference between layers ...

23

Perfluorobutane is inert and has almost twice the density of sulfur hexafluoride. It is non-toxic enough that it is used in fire extinguishers and injected as a contrast agent for ultrasound. Boiling point: $-1.7\ \mathrm{^\circ C}$. Perfluoropentane is similar and rarer but somewhat higher density $(\sim13\ \mathrm{kg/m^3})$ in proportion to its higher ...

22

Actually the densest gas which has an actual use is Tungsten hexafluoride, clocking in at an astounding 13 grams per liter. Tungsten hexafluoride isn't as well known as its lighter cousin, sulfur hexafluoride, because it has a narrow range of uses. It is useful in the field of electronics manufacturing as it can be used to coat circuit boards with Tungsten. ...

20

Dyes and pigments work by absorbing certain wavelengths of light and reflecting or transmitting the rest. When a dye molecule absorbs a photon, an electron is excited to a higher energy state. Most of the time (neglecting fluorescence), the molecule de-excites by giving off heat and returns to the ground state intact. However, because the excited state is a ...

20

Why, when you bring the two bars together so that they touch each other, do they not instantly bond with each other forming one larger bar or block? ... Why do we need to 'weld' two bars together - why don't they just bond on their own? The problem is generally one of two things: gases (air) or metal oxides get in the way. You can actually bond two pieces ...

18

I used F'x answer as a starting point, and I found the mineral. It's called Ulexite. The fibers of ulexite act as optical fibers, transmitting light along their lengths by internal reflection. When a piece of ulexite is cut with flat polished faces perpendicular to the orientation of the fibers, a good-quality specimen will display an image of whatever ...

18

Are there other ways of "chemical strengthening" besides cationic exchange that can be utilized to strengthen the glass, keeping it flexible and less fragile at the same time? In a word: No. To understand why ion exchange strengthens glass, you have to understand why the ion exchange makes the glass harder. The process ion exchange hardening, its done at ...

17

Ron's answer is great, but I'd just like to touch on the mechanisms behind thermal conductivity so we can rationalize the differences between the behaviour of diamond, graphite, and metals: There are two ways in which heat is transmitted through solids: phonons and electronic conductivity. The latter occurs in electrically conductive solids, where ...

17

I would guess radon is the densest gas ($9.73\; \text{kg/m}^3$) that is not directly lethal. It is radioactive however, emitting alpha radiation, so you don't want to breath it in. Given that it is much heavier than air, as long as you don't hug the ground it think it would be possible to be in the same room without killing you. From the fully non-lethal ...

17

Based on your comments, it sounds like you have some sort of colored sand and you want to immobilize it. My suggestion would be some sort of polymer matrix. There are multiple possibilities, but one of the easiest is polydimethylsiloxane PDMS which is optically clear and pretty easy to work with (i.e., safe). There's the "base" and a curing agent which ...

17

Here's the boring answer: Toothpaste is a mixture of some solids and some liquids. The question "is it solid or liquid?" makes sense when you're talking about a substance or a mixture with a single phase—that is, a substance or mixture that's pretty much completely uniform throughout space. Examples of single-phase materials include pure water (a liquid), a ...

16

Metals have several general properties in common (to some degree): Luster - metals are shiny Electrical conductivity - metals conduct electricity Thermal conductivity - metals conduct heat Ductility - metals can be drawn into wires Malleability - metals can be beaten into shapes Fusibility - metals can be melted and forged All of these properties derive ...

15

Well first off, pure ethanol is hygroscopic; it attracts water, to the point that it will pull it out of the air. Ethanol and gasoline will mix, but ethanol, gasoline and water will not; the ethanol-water mixture will come out of solution and settle on the bottom of your tank. Add a little oxygen to the mix, and you get rust. However, the more common side ...

14

Similar to inox for inoxydable (inoxidable), it equally is a French coinage. To tune mechanical properties of iron, mixing additives leads to numerous alloys of iron. In case of rene or rené as contraction of résistant (durable) and on base of Nickel, and is example of the superalloys. This source technologie des métaux et alliages - particulièrement en ...

13

It is Viscous. Viscous mean "having a thick, sticky consistency between solid and liquid"(dictionary meaning) There are many more examples like tomato ketchup, honey, wax, toothpaste, etc. To know more check out Wikipedia

13

Diamond has cleavage planes. If you want something nearly unbreakable, try nephrite, which is a tough form of jade used by the ancient Aztecs to make axe heads! Actinolite is another related "tough as steel" mineral. These minerals are made up of interlocking strands (actinolite) or microscopic fibers (nephrite). But diamond is a regular geometric lattice, ...

12

The bag contains a supersaturated solution of some salt with a highly negative enthalpy of crystallisation, which could be something like sodium acetate ($\ce{Na^{+}CH3CO2^{-}}$). The dissolved salt would really like to come out of solution but lacks a nucleation site. Bending the metal disk produces a transient site where crystallisation can begin, and from ...

12

Teflon (PTFE, polytetrafluoroethylene) is prepared by the polymerization of tetrafluoroethylene as shown below. If we took polyethylene and replaced all of the hydrogens with fluorines, we would have PTFE. Here is a Table that compares the strengths of some single bonds involving a methyl group. \begin{array}\hline Experimental ~Bond~ Enthalpies for~ CH_3 ...

12

Geologists prepare soil profiles for a living. The task is easy in principle - dig a pit, apply glue to the wall, then transfer the glued layer to a sheet of cloth. The practice is really difficult, the glue recipe and transfer technique are trade secrets. See here (warning, German language): http://www.sand-abc.de/sandkorn/lackprofil/lackprofil.htm Why ...

12

Ionic crystals are hard because of tight packing lattices, say, the positive and negative ions are strongly attached among themselves. So, if mechanical pressure is applied to an ionic crystal then ions of similar charges may be forced to get closer to each other. Now, by doing so, the electrostatic repulsion can be enough to split or disorient completely ...

12

In addition to being a non-practicing chemist, I'm also a non-practicing geologist, so look no further for an answer you can trust. Your minerals are classified as follows: C is for color (sample, gross), S is for streak (color of powdered mineral, essentially, on an unfinished streak plate), H is hardness on the Mohs scale, SG is specific gravity, L is ...

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TL;DR I think you might need two more things to interpret this line: the first code part of the standard, and the standard itself - ASTM D2000 (needs to be purchased). These descriptors are not chemical elements, they seem to be the part of ASTM D2000 "Standard Classiﬁcation System for Rubber Products in Automotive Applications", so what you are looking at ...

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Actually, toothpaste is both. I'm no chemist, but I am pretty sure that it can be correctly classified as a semisolid, which means exactly what you'd think. Semisolids have properties of both solids and liquids. Slime would be another example of a semisolid.

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Toothpaste is a colloid. just like dust particles suspended in water form suspension, colloids are much finer particles suspended in a medium. for example jelly, it is solid particles suspended finely in a liquid....and foam; that is gas suspended in a liquid. As such is deodorant spray that is liquid suspended in air(gas)

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First, let's look at gold's properties. Gold is the most malleable of all metals. This malleability alone is very useful in aiding scientists to create such small gold nanoparticles. Gold also reflects infrared radiation very well and is an excellent conductor of heat and electricity. Generally, gold is not easily affected by oxygen and is generally ...

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