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42 votes
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Why isn't the molecule of water linear straight?

There are six electrons in the outer orbital of an oxygen atom. In a water molecule two of these electrons bond with the lone electron of each hydrogen atom to form two “bond pairs”. The remaining ...
gandalf61's user avatar
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24 votes

Can we call rusting of iron a combustion reaction?

Rusting of iron is an oxidation reaction, but not combustion. Although the reaction's equation looks the same as the equations for combustion (e.g., of hydrogen and oxygen mixture, $2H_2+O_2=2H_2O$), ...
Roger V.'s user avatar
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22 votes

Why isn't the molecule of water linear straight?

Let's start by taking a look at the 'bare' oxygen atom. While simplistic depictions of atoms often show the electrons orbiting the nucleus on various circular orbits as if they were planets, quantum ...
Jan's user avatar
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11 votes
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Difference between Reversible and Irreversible processes in Physics vs. Chemistry

Is it possible that reversible physical (thermodynamic) systems are not related to reversible chemical reactions? Correct. No real process is thermodynamically reversible; entropy is generated ...
Chemomechanics's user avatar
8 votes

Difference between Reversible and Irreversible processes in Physics vs. Chemistry

Reversible chemical reactions are not really processes from thermodynamics point of view, i.e., it doesn't make sense to apply to them term reversibility in its physical meaning. It is worth adding ...
Roger V.'s user avatar
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7 votes
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Why is 99% isopropyl alcohol preferred for a DIY cloud chamber?

There is no particular property of alcohols; Wilson’s original cloud chamber used water and worked fine. The essential point of a cloud chamber is to create a supersaturated vapor. Vapors in air have ...
CR Drost's user avatar
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6 votes
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Why soap bubbles are made of soap?

Soaps are surface active chemicals or surfactants. The reason they stabilise foams is that they prevent the water films from collapsing. Conmsider a thin film of pure water: Any liquid film is ...
John Rennie's user avatar
5 votes

What does the subindex $x$ in $\text{Bi}_{1-x}\text{Sb}_{x}$ mean?

Normally the index at an element tells me "how many atoms of that element there are", but in this case we are discussing values of $x = 0.04$ etc. so this does not make sense. That is still what it ...
Emilio Pisanty's user avatar
4 votes

Why exactly does molten NaCl explode, when it is poured into water?

Taken from this answer by user Jan on chemistry SE for the repost of this question there. Understand that sodium chloride is not made up of sodium metal and chlorine gas but of sodium ions and ...
4 votes

Equivalent in wood/coal/methane of one litre of petrol

The best ever IMO is this link which contains data as well as this nice pictorial answer from xkcd (link to original comic here).
ZeroTheHero's user avatar
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3 votes

Why is gaseous carbon dioxide transparent?

The answer here is that color is not a property of elements alone, but rather of the structures formed from them. Graphite, soot, and carbon (mon/di)oxide are all different kinds of structures, ...
The_Sympathizer's user avatar
3 votes
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Pressurizing with nitrogen vs vacuum?

The fact that the process instructions call for 35-50 psi of pressure with an inert atmosphere (N2 or CO2) seriously implies that there is a real possibility of vaporization of some of the monomer ...
David White's user avatar
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3 votes
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What does '%BZ' mean in materials science?

The abbreviation BZ stands for Brillouin Zone, almost universally. The material depicted is not a uniform solid, and it has at least two components each with different sizes of unit cell and thus ...
Emilio Pisanty's user avatar
3 votes
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Role of methane in global warming

Before I give my answer, I need to comment on two points above. First, contrary to a comment made above, methane IS building up in the atmosphere, just not at a large rate. See figure 2 here from ...
CGS's user avatar
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2 votes

Does plasma has any chemical formula?

Actually non of the four stage has any chemical formula because it is just a stage. Like H$_{2}$O is a formula of water not the formula of liquid. CO$_{2}$ is a formula of carbon dioxide not the ...
Edy D Rai's user avatar
2 votes

C60 Macro Ojects

In its superconducting phase, it'll have exactly the same effect on magnetic fields as any other superconducting object like the Meissner-effect. It won't affect gravity other than by its mass - ...
Martin's user avatar
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2 votes
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Is there any non-metallic oxide that remains in solid state at room temperature?

Antimony trioxide is a good example that's also relatively common in nature. If you still think antimony is too semimetallic, then various iodine oxides (e.g. IO$_2$) are solids at room temperature.
probably_someone's user avatar
2 votes
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Why is liquid fat transparent and solid fat opaque?

The same phenomenon occurs with ice/ water, butter, Coconut Oil etc. Let's look at butter. While it is a liquid, it is yellow in color. This means that it is reflecting and transmitting only ...
Aaryan Dewan's user avatar
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2 votes

What is the temperature at which Napalm burns?

Your online research is correct. Napalm relies on oxygen in the atmosphere in order to burn, so it produces just an ordinary flame. Ordinary flames reach equilibrium at less than few thousand degrees ...
Paul Young's user avatar
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2 votes
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What does the subindex $x$ in $\text{Bi}_{1-x}\text{Sb}_{x}$ mean?

If 100% of the medium is composed of the two elements $A$ and $B$, than a easy ways to write the percentages $p_A$ and $$x=p_B=1-p_A$$ is $A_{p_A}B_{p_B}$. Thus, in your case it becomes $A_{1-x}B_x$....
Semoi's user avatar
  • 8,754
2 votes
Accepted

Why does the air pressure not increase when I shake a coke bottle?

Shaking the container distributes small bubbles through the liquid. These act as nucleation points at which the dissolved CO2 can boil out of the solution, much like how water in a steel pan will ...
g s's user avatar
  • 13.6k
2 votes

Strange occurrence of glue drying

Superglue hardens from the surface because curing is driven by humidity from the air. From what we are seeing I assume that during curing the layer expands (this is the case for drying oils like ...
Sebastian Riese's user avatar
2 votes

Strange occurrence of glue drying

Adhesives typically shrink when hardening. They obviously also get hard when hardening. Depending on the particulars of the adhesive, sometimes it wants to keep shrinking well after its viscosity has ...
W_vH's user avatar
  • 191
2 votes

Why can a material mixture block all light?

If you are referring to "all light," it's important to clarify that you mean visible light, as other types of light, such as radio waves and x-rays, would most likely pass through your ...
Bill Alsept's user avatar
  • 4,073

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