# Tag Info

32

Play-Doh is mostly flour, salt and water, so it's basically just (unleavened) dough. There are a lot of extra components like colourings, fragrances, preservatives etc, but these are present at low levels and don't have a huge effect on the rheology. The trouble with saying it's basically just dough is that the rheology of dough is fearsomely complicated. ...

16

Fire is neither. Fire is a process involving both. Fire is the energetic combination of various substances with oxygen to release light and heat. In a gas fire, such as might be found on a stove or in a heater, a light hydrocarbon such propane is broken down into components of hydrogen and carbon which unite with oxygen from the atmosphere to form water ...

11

Yes, of course, the freezing point will decrease by the pressure developed, while part of the water freezes. But do not underestimate the pressures! In such an experiment easily some thousand bares may be developed. (Depends on the rigidity of the vessel and the volume of water) Here is a video showing how freezing water cracks a cast iron sphere. ...

7

In simple terms, there isn't any space in the ice crystal lattice for the extra atoms and there is no way to plug either of the ions (or the whole salt molecule) into the growing pattern. So more and more water joins the frozen mass, leaving a more and more concentrated brine until essentially all the water is frozen and the salt remains behind. As ...

6

I suggest that looking for an explanation for 'fire' may be the wrong approach. Science is a process where we try to explain what we perceive. In doing so, we may have to sacrifice (or at least temporarily suspend) a common perspective. My presumption is that you are probably mostly interested in the visual manifestation of fire - the dancing flames. ...

6

A quick comment on your terminology. The description "non-Newtonian" just means the stress/flow rate graph is not linear i.e. there isn't a single constant viscosity coefficient. The fluid you describe is what we colloid scientists call "dilatant", and it is certainly non-Newtonian. However there are lots of other non-Newtonian fluids such as tomato ketchup ...

6

Liquids are a state of matter in which the atoms or molecules are held together by chemical bonds (a difference from gases) but the bonds are weak enough for the shape to be variable (a difference from solids). That's why it is not possible to increase or decrease their volume much; the amount of energy from these chemical bonds would rapidly increase ...

6

@MartinBeckett's already gave an excellent answer: Salt is excluded from ice because there is "...no way to plug the ions... into the growing [ice] pattern." This unusually long answer -- a mini-tutorial really -- is an expansion on his answer. I've added a long background section that uses informal, easily visualized analogies to define a number of related ...

6

I'm going to guess the toy you actually have in mind is the stuff sold in the US under the name Silly Putty . Play-Doh is used primarily as a "modeling clay" for sculpture - which means it needs to behave as a "plastic" - it's yield strength needs be low enough to enable it to be worked into a figure, but high enough that reasonable sized figures don't ...

6

While the physical properties of a solid vs a liquid are obvious to any grade-schooler, the physics behind it are a little more complex. A substance is traditionally called a solid if it will not noticeably deform from a given starting shape in its steady state (in simple terms, it will not "flow" in the absence of any force other than gravity). A liquid, ...

6

In the case of liquids and gases, at least, there's no fundamental difference. To see this, take a look at Wikipedia's phase diagram for water. Ignore the dotted lines for the moment, and note that the line between vapour (steam) and liquid stops at a certain point, called the critical point. What this means is that if you go through the following ...

5

Plasmas are a common part of the world we live in. The definition of plasma allows them to exist within an environment consisting mostly of bound atoms. A variety of human technology creates plasmas. The type I hear plasma researchers reference most is a simple RF Plasma. This is perhaps the most direct way to use electricity to shake off the electrons ...

5

In the absence of salt, the ice and water at 0C are in equilibrium, so unless you add or remove heat nothing changes. However when you add salt it reduces the freezing point of the water. This means the ice and salt water are no longer in equilibrium, and the result is that the ice starts to melt. Melting the ice requires heat. Specifically it requires the ...

5

I can address one class of non-Newtonian fluids consisting of solid particles dispersed in a liquid medium, such as the cornstarch and water mixture commonly called "oobleck." In more scientific language, I am talking about concentrated colloidal suspensions of particles. Here is an image of oobleck, taken from Dounas-Frazer et al 2012. These fluids tend ...

5

Good question! The defining difference is that in a gas the atoms are intact, and in fact are typically bonded into molecules, whereas in a plasma at least some of the electrons separate entirely from their atoms. In other words, particles of a plasma are charged, but particles of a gas are mostly uncharged. So technically, a plasma is not a gas and it ...

4

The fluorocarbon in the can is a liquid under pressure. When you spray the can upright, only the fluorocarbon vapor at the top of the can is released. When you turn the can upside-down, the liquid is forced out instead. As you have noted, this liquid quickly evaporates because is is a gas at room temperature. In other words, it begins to boil. This carries ...

4

There is a difference even in the classical wave framework between sound and light. Sound propagates on a medium, light propagates in vacuum with no problem . Where would we be if sunlight were like sound, never propagating through vacuum? In the classical framework, before special relativity was posited and proved, in order to make the equivalence you ...

4

The two hydrogen atoms aren't in the same state in the situation you described: they differ by the location which is an observable specifying the quantum state. Because it's different, the states are different. Moreover, hydrogen-1 isn't a fermion. If you talk about two electrons in the potential of two hydrogen nuclei, then you do have two fermions, but ...

4

See Wikipedia for a list of available plasmas over there..! Or have a look below for the chart which shows variation of temperature and electron density in different plasmas..! A quick Googling would've provided the answer. Common examples include Lightning..! The Sun (from Core to Corona) Fluorescent Lights and Neon Signs Nebulae (Luminous Clouds ...

4

Yes, rocks are solids, though not all of them will have frozen and there's a minor complication about what we mean by freezing for some rocks. Firstly note that sedimentary rocks formed by chemical processes so they were never liquid. So although these rocks are solid, they haven't frozen. In fact you can't even melt carbonate based rock because it ...

4

For clarity, there is a common misconception about plasma here. Plasma when being introduced for the first time to someone who doesn't know what it is, it is called "The fourth state of matter" which is an inaccurate description of it. Since this term is used for introducing some one to plasma, it is no big deal. When a material changes from a distinct ...

4

"Burn" and "melt" are completely different things. "Burning" is a chemical reaction, usually with the oxygen in the air (or any oxidant, really). In organic burning, like the cake you suggested, the carbon compounds react with atmospheric oxygen, producing carbon dioxide, water (vapour) and (sometimes) an ashy residue. "Melting", on the other hand, is a ...

4

Substances in solution have the effect of decreasing the temperature of the freezing point of the liquid they are dissolved in. This is called freezing-point depression. This is one of the reasons why adding salt to ice helps it melt. Your coke is a complicated solution + colloid and sugar is one of the main substances dissolved in it. During freezing: ...

3

If by highest, you mean temperature (proportional to mean kinetic energy of the particles), then the plasma state is "higher" than the other states you list. I think that there are other "higher" states of matter. For example, when it becomes energetically favorable for protons and electrons to combine into neutrons, you get a state called "neutron ...

3

Related note: Fission isn't exactly turning matter into energy. It just releases the binding energy of the nucleus. This binding energy is part of the measured mass pf the nucleus, but if you want to separate "matter" and "energy" (not really possible), then it counts as energy. $\newcommand{\a}[3]{\mathrm{^{#1}_{#2}#3}}$ ...

3

In what ways can energy transform into matter and vice versa? Energy and matter are connected according to special relativity and this has been experimentally demonstrated . It is the famous formula: $E=mc^2$ , where $m$ is the relativistic mass and $c$ the velocity of light. or $E^2=m_0^2c^4 +p^2c^2$ , for a particle with rest mass $m_0$ moving ...

3

Gases are very simple systems. Just consider a hallmark of all gases, the ideal gas. There are no interactions among the particles there. The real-life gases do have some interactions but these can be treated as perturbations of ideal gas. Of course, at certain portions of the phase diagrams gases are more complicated. I am talking about transition lines to ...

3

Are you ready to jump into a pool with pressure of about $50\times 10^5pa$ ?? Yes, $P_c$, critical pressure of carbon-di-oxide is about $5.1\ atm$, that too at about $-50^0 C$. So, a pool with liquid $CO_2$ will never be opened for a bath! Also at room temperature this will go above $50atm!!$ This would happen if you try turning it into liquid. ...

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