Study of macroscopic and microscopic phenomena in chemical systems in terms of physical laws and concepts [thermodynamics, statistical mechanics, kinetic theory, quantum mechanics...].

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22
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2k views

Could the Periodic Table have been done using group theory?

These three questions are phrased as alternative-history questions, but my real intent is to understand better how well different modeling approaches fit the phenomena they are used to describe; see 1 ...
21
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3answers
13k views

Why does the water rise?

It's a very popular experiment (eg), from elementary school : put a burning candle on a dish filled with water, cover the candle with an inverted glass: after a little while, the candle flame goes ...
20
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3answers
31k views

Why do grapes in a microwave oven produce plasma?

Some of you may know this experience (Grape + Microwave oven = Plasma video link): take a grape that you almost split in two parts, letting just a tiny piece of skin making a link between each ...
18
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3answers
1k views

Why the distribution of elements on Earth?

I've been wondering exactly why the elements are distributed the way they are on Earth. The heavier elements have their origins in the centers of stars, or in supernovae. After the death of the stars, ...
17
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5answers
3k views

When I stretch a rubber band, it breaks. When I hold the broken ends together, why doesn't it join again?

The question is simple. When we join the two broken surfaces, what is it that keeps the surfaces from connecting with each other, while earlier they were attached to each other? Also, would the two ...
17
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4answers
2k views

Boiling water and salt

I would like to have a good understanding of what is happening when you add salt to boiling water. My understanding is that the boiling point will be higher, thus lengthening the process (obtaining ...
16
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5answers
10k views

How was Avogadro's number first determined?

I read on Wikipedia how the numerical value of Avogadro's number can be found by doing an experiment, provided you have the numerical value of Faraday's constant; but it seems to me that Faraday's ...
15
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6answers
3k views

Where should a physicist go to learn chemistry?

I took an introductory chemistry course long ago, but the rules seemed arbitrary, and I've forgotten most of what I learned. Now that I have an undergraduate education in physics, I should be able to ...
13
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3answers
344 views

Chemical reaction as state transition?

When considering diffusion of chemicals, the reaction part is business of chemical kinetics, where the relevant characteristics of different substances come from collision theory together with some ...
11
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7answers
8k views

Explanation of “thermite vs ice” explosion

There are several videos of the reaction, where some amount of burning thermite explodes on a contact with ice. An "original" video: http://www.youtube.com/watch?v=IuPjlYxUWc8 A Mythbusters ...
9
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4answers
9k views

Why does ice have a lower density than water?

Can someone explain me why is ice lighter than water? As I know, all solids are usually heavier than the liquids (correct me if I am wrong).
8
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2answers
2k views

Is the Mendeleev table explained in quantum mechanics?

Does anybody know if there exists a mathematical explanation of Mendeleev table in quantum mechanics? In some textbooks (for example in F.A.Berezin, M.A.Shubin. The Schrödinger Equation) the authors ...
8
votes
4answers
5k views

Why do covalent bonds form?

why in a covalent bond are "the bonded electrons are in a lower energy state than if the individual atoms held them at the same proximity"? Also is it correct that " I think when you start pushing ...
8
votes
3answers
3k views

What makes the difference between ionic and covalent bonds?

Backstory: When I learned about chemical reactions, there were two types of molecular bonds: Ionic, where an atom or compound molecule with a low valence number loses those valence electron(s) to one ...
8
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3answers
780 views

What is the angular momentum spectrum of an sp${}^3$ electron?

So, one thing has been annoying me ever since I learned about orbital hybridization: you explain the shape of molecules by postulating that the orbitals of multi-electron atoms are linear combinations ...
8
votes
3answers
775 views

Is mass-energy conversion in chemical reactions experimentally observable

This is a common point of argument on internet forums. I think it is fairly well established theoretically that there is a very small amount of mass converted to energy in an exothermic chemical ...
8
votes
2answers
431 views

Explaining valence with quantum mechanics

Can anyone give me a quantum mechanical explanation of the theory of valence? (i.e. why atoms bond just enough to have a complete orbital) EDIT: To clarify, I already have an idea of why atoms bond, ...
7
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3answers
1k views

What is the quantum mechanical explanation of the octet rule?

What is the quantum mechanical explanation of the octet rule? In other words, what makes the octet rule be true from a quantum mechanical view? How we explain what makes some atoms don't follow the ...
7
votes
2answers
24k views

Why does a salt solution conduct electrical current?

How does e.g. sodium chloride (aq) conduct electricity? By accepting electrons (unlikely since they already have a full outer shell)? But they can't be hopping around themselves, can they? I mean, if ...
7
votes
2answers
2k views

Why is quicksilver (mercury) liquid at room temperature?

This is a nice question when you find it out, and I am really looking for a proper answer. Take quicksilver (Hg) in the periodic table. It has one proton more than Gold (melting point 1337.33 K), and ...
7
votes
2answers
146 views

Why is salt so hard to remove from water?

Water molecules and various salt molecules are very different. However, it seems very difficult to separate the two. Once a salt is dissolved in water, an energy or chemical intensive method (like ...
7
votes
1answer
127 views

Does an electric field create a pH gradient?

Since pH is a measure of the effective concentration of $\mathrm{H}^+$ ions a solution, I expect that an electric field applied to a solution will create a pH gradient. The higher concentration of ...
7
votes
3answers
230 views

Why does ice melts, waits for 100 degrees and THEN vaporises? Why is not the process of expansion of things continuous?

What I am asking is this: Why can't a body be solid, then solid-ish, then solid-like, then liquid-like, then liquid-ish, then liquid, then vapor-like and then vapor? Why is there a rigid temperature ...
7
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2answers
385 views

How much Bicarbonate of Soda and Vinegar would I need to reach space?

So here is my problem - as part of my job I present some science demonstrations to children and one of the tricks I regularly use is the bicarb/acetic acid rocket. I thought the other day that a ...
7
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1answer
75 views

What would be the first compound formed in the early universe?

This may sound like a chemistry problem, but I suspect this would have lot to do with primordial nucleosynthesis. After all physics underlies everything. It is believed that several elements were ...
6
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4answers
3k views

Why is the canonical ($NVT$) ensemble often used for (classical) molecular dynamics (MD) simulations?

Molecular dynamics (MD) simulation is a common approach to the (classical) many-body problem. It relies on integration of Newton's equations of motion to simulate the trajectories of many (e.g., ...
6
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2answers
2k views

How are the calories in food calculated?

This is intended to be a fun question. Calorimetry used for calculating the heat generated from chemical changes has been around for centuries, however, I suspect the process for calculating food ...
6
votes
1answer
233 views

Steam above meal

When I fry something on the pan and the fire is big and intensive (the flame over the pan), there is no stean above the pan or just a little. But when I turn off the fire, suddenly the steam appears, ...
6
votes
1answer
438 views

What is the purpose of a “protect from light” warning?

Some food or medical items, like rasberry juice concentrate I just bought, have a "protect from light" warning on the label. How can light influence products like milk and what does this warning mean ...
6
votes
1answer
217 views

Why can we skate on ice? [duplicate]

I have known the reason why skate can slide over ice is that water's melting curve in terms of pressure and temperature has a negative slope. If the pressure due to our mass increases sufficiently ...
6
votes
2answers
144 views

Handling halogen lamps

When consulting manuals, electricians, online sources, etc., they always instruct you to handle halogen light bulbs with gloves. The "explanation" that usually accompanies this statement is that oils ...
6
votes
2answers
393 views

Statistical Mechanics treatment of the reaction process?

I'm searching for an at least semi-rigorous Statistical Mechanics description/treatment of a (spatially resolved) chemical reaction process of a macroscopic portion of at least two different species ...
6
votes
1answer
335 views

What is the most stable nuclide of an isobar?

From the semi-empirical mass formula, the mass of an atomic nucleus is $$M\left(A,Z\right)=Zm_p+(A-Z)m_n-\frac{E_b(A,Z)}{c^2}$$ I've been told (at first) that for a given mass number $A$, the most ...
6
votes
1answer
301 views

Donors/Acceptors in Metal Oxides

Can anyone explain to me why most articles describe chromium as an acceptor in titanium dioxide? In TiO2, titanium has the charge state Ti$^{4+}$ and oxygen has the charge state O$^{2-}$. When Cr ...
6
votes
7answers
2k views

Is there any reproducible tested evidence for Ni-H cold fusion?

The main replications of cold fusion, the ones that are beyond reproach, used Pd/d as the system. But commercial developers have often claim to use Ni-H to achieve similar effects. The claims include ...
5
votes
2answers
341 views

Solidification by the application of heat

When you add heat to a liquid (or a fluid), can it be solidified? If not, why in the world does an egg's stuffs become solid (or at least no more a liquid) when you 'boil' it in water?
5
votes
2answers
5k views

Why are the noble metals inert?

I am wondering: The noble 'gases' are inert because they have closed shells and don't want to give that up. But the noble metals, such as Copper, Silver, Rhodium, Gold, don't seem to have this. For ...
5
votes
3answers
746 views

Why is Avogadro's hypothesis true?

Why is the number of molecules in a standard volume of gas at a standard temperature and pressure a constant, regardless of the molecule's composition or weight? Let's say I have a closed box full of ...
5
votes
4answers
6k views

is it possible to flow current in open circuit?

First , i don't know much about chemistry and physics. I'm just a graphic designer but i have this question in my mind. I'm sorry if this question is too basic and use 'generic' language. As i know ...
5
votes
3answers
296 views

Do electrons in multi-electron atoms really have definite angular momenta?

Since the mutual repulsion term between electrons orbiting the same nucleus does not commute with either electron's angular momentum operator (but only with their sum), I'd assume that the electrons ...
5
votes
2answers
378 views

Can we fully simulate molecular physics?

Is our knowledge of physics complete enough to achieve fully natural simulations of molecular interactions in a computer simulation? How far off are we? Reason for question: I wonder how far we are ...
5
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2answers
1k views

What happens to chemical compunds that include radioactive nuclei, when those decay?

Say you have a chemical compound made up of one or more radioactive nuclei. If the nucleus decays, does the compound? Possible outcomes I can think of: the compounds continues to exist if a ...
5
votes
1answer
3k views

Can a saltwater solution conduct electricity forever? [closed]

We know that very pure water does not conduct electricity, but salt water is a decent conductor. This is commonly explained by saying that "the ions carry the current through the solution", an ...
5
votes
2answers
339 views

In condensed matter simulations, how is particle number density computed in practice?

I have been reading a recent paper. In it, the authors performed molecular dynamics (MD) simulations of parallel-plate supercapacitors, in which liquid resides between the parallel-plate electrodes. ...
5
votes
1answer
242 views

What equation describes the electrostatic potential in these circumstances?

I have a solver for Poisson's equation and it works nicely. It uses finite differences. It works in the presence of multiple dielectrics. It also solves the Poisson Boltzmann equation. That is, fixed ...
5
votes
2answers
312 views

The AntiBonding Orbital with Shrinking Interatomic Distance

I guess this is more of a chemistry question, but whatever. I think it's interesting. Suppose you had two bare atomic nuclei. For concreteness, lets assume the nuclei are the same with atomic ...
4
votes
5answers
531 views

Is there no radioactive decay between nuclear fusion and solid material formation?

I'm aware my question might be considered a duplicate of this one: Radio-dating and the age of the earth I read that one and I looked everywhere and I still can't find my piece of mind. I would ...
4
votes
2answers
444 views

Frequency of touch, taste, and scent [closed]

So I was thinking about sound - and how anything below 20Hz is basically inaudible to humans (because it is too low of a frequency to be recognized), as well as anything above around 20KHz (because it ...
4
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3answers
687 views

Nanorobots. What stops us from producing them yet?

If we can already predicts accuratelly motion on molecular levels, what stops us from developing small robots to, for instance, navigate through our blood vessels looking for cancerous cells and ...
4
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2answers
241 views

Acer saccharum (Sugar Maple) Sap & Freezing

This may or may not be the appropriate scientific discipline to ask this question of, but I'll give it a shot. I'll happily invite chemists to chime in as well. It's time to tap sugar maples in the ...