106 votes
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Is toothpaste solid or liquid?

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 ...
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  • 6,590
81 votes

Why can a diamond be broken using a hammer if it's the hardest natural substance known?

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 ...
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45 votes

Why isn't 'chemically-strengthened glass' made with potassium carbonate to begin with?

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 at the surface that does. To understand why ...
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44 votes

Is toothpaste solid or liquid?

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 ...
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  • 5,487
32 votes
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Which is the densest gas known?

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 ...
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30 votes
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Why does diamond conduct heat better than graphite?

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 ...
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30 votes

What easily accessible material has melting point between 500 °C and 590 °C?

Temperature-indicating or thermo crayons are used by welders. These melt at specific temperatures. Not as an endorsement, but to give you an idea of what's available, the crayons from McMaster-Carr ...
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26 votes

Which is the densest gas known?

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 ...
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  • 523
26 votes

Why isn't 'chemically-strengthened glass' made with potassium carbonate to begin with?

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 ...
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22 votes

Is toothpaste solid or liquid?

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 ...
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22 votes
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Why does sunlight cause colors to fade?

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 ...
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21 votes

Which is the densest gas known?

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 ...
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21 votes

Why does diamond conduct heat better than graphite?

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 ...
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21 votes

If you put two blocks of an element together, why don't they bond?

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 - ...
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20 votes
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What makes Gorilla Glass more durable with each generation?

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 ...
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20 votes

What is the @ symbol used for in material science?

The at symbol @ universally means "at the site" or "at the rate of". It is routinely used in supramolecular chemistry to denote guest@host relationship because it follows the ...
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20 votes
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Why use diamond-like carbon instead of diamond?

You balance cost of manufacture and return of investment for the anticipated use. If you read about the methods of production of diamond-like carbon (DLC), e.g., on Wikipedia, e.g. «DLC is typically ...
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18 votes

What easily accessible material has melting point between 500 °C and 590 °C?

It might not qualify as 'available at home' but MakeItFrom has a database with engineering material you can search: MakeItFrom.com is a curated database of engineering material properties that ...
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17 votes

How to solidify sand

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 ...
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15 votes
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Why are so many ionic compounds brittle?

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 ...
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15 votes

Conception and manufacture of the Avogadro Project's (nearly) perfect silicon sphere (and, what is “atomic feeling”?)

Short answer: The success of the project benefitted from many contributors. According to BIPM and its Avogadro project, there are two spheres (reference). The page equally refers to a publiction ...
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14 votes

Is toothpaste solid or liquid?

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 ...
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14 votes

Is toothpaste solid or liquid?

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 ...
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14 votes
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What does "René" mean in René alloys?

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 ...
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14 votes

Why can a diamond be broken using a hammer if it's the hardest natural substance known?

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 ...
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14 votes
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Can a vacuum on a closed system really “pull” things out of it?

Gasses don't get "pulled", they get "pushed". When you empty a neon tube, you attach a device with almost no air in it to mouth of the tube. The air that is in the tube then pushes ...
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13 votes
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What makes teflon such a strong material?

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 ...
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13 votes

Is toothpaste solid or liquid?

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 ...
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13 votes

Is there a material that ions can pass through but water can’t?

There are so many materials that allow the passage of ions but not water. They are called ion-exchange membranes. I believe you are interested in water purification based on your previous posts. The ...
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12 votes

How to solidify sand

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, ...
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