Questions tagged [physical-chemistry]

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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$CO_2$ heating experiment (high school)

A student is trying to run some experiments for a project to explore how the concentration of CO2 affects the temperature of air. For this, she: Drops different ammounts of dry ice (between 0 and 2....
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Chemical reactions in fluids

The equations of motion of ordinary relativistic hydrodynamics are derived by considering conservation equations of the energy tensor and particle number current, where constitutive relations relate ...
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Relation between oscillator strengths $\log{gf}$ and the Einstein $A$-coefficient, rotational quantum number, …

I'm analyzing the spectra of M dwarfs. Some authors characterize the lines with the oscillator strengths $\log{gf}$ while others follow different paths with the Einstein $A$-coefficient. I would like ...
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Entropic Restrictions to Water Interfaced with Hydrophobic Molecules

The occlusion of hydrophobic molecules from polar solvent such as water, I have read, is an entropic effect. My question is pretty simple -- at an interface of water and oil, or in the clathrate cage ...
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What Gas Law does one get from a Lennard-Jones Potential

Given a potential, at low density we can approximate high order potentials as a sum of two-particle potentials. Given such an approximation, using a Lennard-Jones 6-12 potential, one can obtain a full ...
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Increasing the melting point of metal

I need to know how one can increase the melting point of a metals like steel, tungsten or ... about 500 degrees and without destroying its shape?
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Does a proton have a binding energy?

When calculating the $Q$-value, $Q = \Delta M \cdot c^2$, of this reaction: $$ ^6Li \ (\alpha, p)\ ^9Be \quad \iff \quad \alpha + \ ^6Li \ \longrightarrow \ ^9Be + p $$ The $Q$-value can also be ...
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65 views

Why is detailed balance required for thermodynamic consistency?

why does the Wegscheider condition or detailed balance have to be true for chemical reactions and what does it mean to violate it in terms of thermodynamics? here is an attempt to derive a simple ...
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Dimensional analysis with derivatives, logs, exponents and trigonometric functions

How should we do dimensional analysis when we have derivatives, logs, exponents and trigonometric functions in an equation. Should we assume that the operands are pure dimensionless numbers? Coming ...
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Does freezing point depression also affect the speed at which something melts?

If you have a pure water frozen, then it should begin to melt if you apply 33°F air to it. If you have impure water that's frozen, it's melting temperature might have dropped to 30°F. If you apply ...
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How much air could an activated charcoal bag or baking soda box actually purify / deodorize?

Someone I know recently bought a set of small stylish and expensive cloth bags (roughly paperback book sized) filled with activated bamboo charcoal, that you place in a room and it purportedly ...
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Another Free Energy Question :P :)

Hello StackExchange users. Before you read my question I would like to thank you for taking the time to help me out :). So anyways, my question is about the formation of coal seeming to break the laws ...
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Why don’t ALL polymers collapse even when their compact state would clearly be favoured in terms of having a lower Helmholtz free energy?

This question is based on example 8.3 in Molecular Driving Forces, Dill and Bromberg (https://books.google.ch/books?id=1gYPBAAAQBAJ&pg=PA136&lpg=PA136&dq=polymer+collapse+a+toy+model&...
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Reference for the electronic levels of the nitrogen atoms resulting from the dissociation of the nitrogen molecule

I would like to know a book or paper that makes a detailed description of the electronic levels of the nitrogen atoms, N+N, resulting from the dissociation of the nitrogen molecule, N$_2$, also at a ...
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75 views

In chemical compounds, where does the “magic” come from in atomic “magic numbers”?

It is well known that atoms with a full electron shell are more stable, it is one of the first facts taught in a middle school Chemistry course: "An element whose atoms have no electrons outside ...
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If we need the term/concept of “isotope”, or why we call them “elements” of the periodic table

I just read this: A nuclide is a species of an atom with a specific number of protons and neutrons in the nucleus, for example carbon-13 with 6 protons and 7 neutrons. The nuclide concept (...
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How is water heavier than petrol, even though its molecular weight is less than petrol?

Molecular weight of petrol is so much higher than water, but when it comes to physical property, weight, one litre of water weighs more than one litre of petrol. How is it possible?
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Conditions to dissolve $CO_2$ in water?

I hope this question is appropriate for the Physics SE, although it involves a practical situation rather than inquiring purely about theory. I've been trying to create carbonated water at home using ...
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Water from air concept – is this plausible?

Here’s an idea I had: Consider how a rocket stove works.. There is an inlet where wood is fed into the stove and an outlet for which the exhaust can vent. Very simple but very effective. Now apply ...
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57 views

When to include chemical potential in Gibbs equations?

I'm struggling to understand when to and when not to include the chemical potential in the differential forms of the thermodynamic potentials. In principle I would assume that any system wherein the ...
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How much energy is needed to make fire?

I'm so curious about fire. So I searched a lot in the internet. And now, I knew that fire is some kind of chain reaction and combustion energy make the other molecule hot and the other molecule makes ...
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How to deduce the SK (Slater-Koster model) integral for two-center with px, py orbital?

I would like to get the Slater-Koster integrals from formula: $$ \sum{R_j}expi\textbf{k}\cdot(R_j-R_i)\int\psi^*_n(\textbf{r}-\textbf{R}_i)H\psi_m({r}-\textbf{R}_j)d\nu, $$ (1) where the sum is ...
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Incompatibility between the Bohr-Sommerfeld quantization condition and the Dunham expansion

I'm trying to apply the RKR (Rydberg-Klein-Rees) method which computes the classical turning points, $a(E,J)$ and $b(E,J)$ of a diatomic molecule for a rotational-vibrational energy value E, and ...
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52 views

How are atoms supported on each other in a material?

Suppose we have a ball made up of iron. There are a "lot" of atoms in the ball. My question is "how" are the atoms supported on top of each other? And, is it due to the repulsion of electrons the ...
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1answer
55 views

Will the mass of a stick of dynamite be conserved when it is exploded?

If a stick of dynamite is blown up in a hermetically sealed chamber, the mass of the chamber and fragments, the heat, sound, and light would still be equal to the original mass of the chamber and ...
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25 views

Which reference should I use for molar masses of chemical elements?

This question is more related to the academical application of Physics than to Physics per se. I'm currently doing my thesis, and it involves a lot of molar masses in the calculations. I would like to ...
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Convert Normal water to cool instantly [closed]

Is it possible to convert the hot/normal water to cold steam instantly(may be within 1/2hr) without using refrigerators etc. If yes, how far can the cold steam travel. I am not sure with all the fluid ...
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55 views

Minimal work required to produce ice at room temperature

I'm wondering about the most efficient way of producing ice from water at room temperature. First of all: why, in principle, do we need to put in work to do so, if water gives off energy while ...
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2answers
234 views

Are there any types of lasers that emit orange and yellow light?

That is, without the introduction of nonlinear optics for frequency multiplication. In the case of orange light, I've often wondered in orange minerals like Lead Molybdate (PbMoO4) fluoresce the way ...
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29 views

Sintering of Yttrium barium copper oxide

I will do an experiment on superconductors, specifically $\text{YBa}_2\text{Cu}_3\text{O}_7$, and I am curios about some steps in the preparation. The starting materials are $\text{Y}_2\text{O}_3$, $\...
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1answer
35 views

Why are processes where $\Delta G \le 0$ considered spontaneous?

I understand how, for any process where starting pressure and temperature start and end points are the same, that $$\Delta G \le 0$$ But I don't see how, from looking at this, that when $\Delta G$ ...
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50 views

Predicting pressure of propane gas in container based on temperature

I'm a mathematician and computer scientist, and for this particular problem I would benefit from some physics/chemistry expertise. I've already asked this question on chemistry stack exchange, but I ...
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Will the refractive index of a electrolyte change when chemical reaction happens?

Since polarization is the reason of refraction, then anything that changes the structure of molecule, atom, or electron will present as a change of reflection. Thus, to my understanding, chemical ...
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Why is grass green? [closed]

How come grass isn't blue or pink, but apparently, it is according to this scientist it is every color but green. I also got told by my teacher that grass is only green and no other color. So I am ...
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Why doesn't increasing the temperature of something like wood or paper set them on fire?

Imagine we have paper book. If we put this into a pan and increase its temperature, this book would not catch on fire. If on the other hand the book interacts with this heat source directly, it does ...
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How to properly align my relaxed molecule onto my gold electrode?

the question is described below since it can be considered a chemistry or physics question: How to translate from one plane to another? originally posted on mathematics SE I am trying to get ...
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Procedure for “reduction” of thermodynamic derivatives in multi-component systems

I am trying to better understand how the "Reduction of Derivatives" (see e.g. Callen Chpt. 7) works in thermodynamics for multi-component systems. All questions are at the bottom. In a closed system, ...
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Why don't we use ionized neon for arc jets?

On a typical arc jet there is a cone in the proppelent stream (ammonia or hydrazine) that acts as an anode and the the nozel itself is the cathode. But why don't we use ionized neon as the cathode and ...
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Concept of polarization in microwave rotational spectroscopy

I am trying to understand the concept of polarization of molecules after they are excited by a microwave pulse. The context is: The complexes are produced in a pulsed supersonic jet expansion of a ...
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Theoretical physics for better batteries?

It is Earth day, so I started thinking about the theoretical physics problems that could help reduce greenhouse-gas emissions and fight climate change. We actually have a reasonable range of ways to ...
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37 views

What would happen if you dropped a stick of dynamite from a high place?

If you were to drop a stick of dynamite from a high place, what would happen once it hit the ground, and why?
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51 views

Was it ever experimentally verified whether antimatter can form chemical bonds the same way matter does?

It's "common knowledge" that antimatter only differs from matter in its charge, and if left alone, it would behave exactly as matter does. This would infer that atoms of antimatter would form similar ...
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Do different liquids have different distributions of kinetic energy of their particles, and does this influence their vapor pressure significantly?

This is a bit of a cross-over between a physics and a chemistry question. When we say a liquid has temperature $T$ we make a statement about the mean kinetic energy of a particle in that liquid. That ...
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2answers
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Why is gaseous carbon dioxide transparent? [closed]

Some carbon-heavy products of combustion, e.g. soot, are black, as is carbon in other forms, e.g. graphite. This seems to suggest that carbon is black. But then how can $\text{CO}$ (carbon monoxide) ...
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Branch of Physics that Examines Atoms Relationships

Is there a specific branch of physics that can examine and calculate the strengths of atomic or molecular bonds and predict how they are going to break, putting into consideration the surrounding ...
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What molecular distribution models apply for nonequilibrium systems as cold stars?

Maxwell-Boltzmann distribution function describes well the distribution of ideal particles in thermal and chemical equilbrium (the concentration of the species is constant). Which models would apply ...
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1answer
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Red colour of the Great Red Spot

In Wikipedia it is mentioned: "It is not known exactly what causes the Great Red Spot's reddish color. Hypotheses supported by laboratory experiments suppose that the color may be caused by ...
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Does the relation between energy and mass, proposed by Einstein hold true for all forms of energy? [duplicate]

I don't have a strong chemistry background, but I recently stumbled upon an answer that concluded that when supplying a reactant(s) with energy E it should be that the difference between the masses of ...
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Does soap repel water?

Yesterday when I was taking my bath, I scratched my soap bar a bit and threw that bit on the shower floor. There was a little amount of water on the floor where that soap bit fell. To my surprise, I ...
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Why microwave oven makes dried bread soft?

This is an old age trick: if you have some bread that became dried and you put it in the microwave few tens of seconds (10 to 30 for top results) you get a nice soft and warm loaf as if it just came ...