1

Geology, Palaeontology & Archaeology / Re: To what extent can Biblical accounts of Noah's flood be believed?

« on: Yesterday at 12:48:55 »

None of the stories in the old testament are to be taken as fact. My understanding is that when they were first written (over the course of multiple centuries, by different groups of people http://www.ancient-hebrew.org/articles_authors.html ), no one expected the stories to be taken literally (in fact the bible contradicts itself multiple times--allowing for much more complex analysis by the scholars--and contradicts physical possibility many times as well). Instead the stories are meant to be fables, and only in the centuries after the new testament did it become mainstream to believe that it actually happened exactly as it was written. (possibly due to the philosophical influences of christian and muslim schools of thought.)

2

Physiology & Medicine / Re: Is there such thing as emotional violence?

« on: 17/09/2018 21:38:47 »

Emotional abuse is definitely more likely to be a problem in close relationships (as in family, school or work), when it is hard or impossible to avoid interaction, and especially when there is an inherent asymmetry to the relationship (parent-child or boss-underling), but it is definitely possible for a single interaction to be emotionally abusive and devastating.

I would count terrorism as primarily an emotional weapon. Yes, there are often some victims who are physically injured or killed, but the primary target is the psyche of a community. Also threats of physical or social harm can be particularly hurtful even when made by a stranger in passing.

There are ways to protect oneself from emotional attacks, but context is very important, and can change what might be appropriate, so I don't want to just suggest random strategies without knowing more, other than: if it feels harmful, it probably is, but that doesn't necessarily mean that it's malicious (some people are just clueless @$$h0les)

3

Chemistry / Re: Why are the half-filled and fully filled orbitals more stable?

« on: 09/09/2018 21:46:54 »

The exchange benefit comes whether the orbital is filled or not.

If all p orbitals are half filled, then there are 3 equivalent electrons (one in each p orbital, and all with the same spin, let's say it's "up"). If all the p orbitals are filled then there are two sets of 3 equivalent electrons (the three "up" electrons can exchange, and the three "down" electrons can exchange.)

4

Chemistry / Re: Is there a complete searchable chemical reaction database?

« on: 30/08/2018 23:17:21 »

There are several, but I am not aware of any that is cheap.

scifinder (from ACS) and reaxys (from Elsevier) are the two that I use (payed for by the institution I work at).

These allow for structural input (exact, partial, or similar), and other parameters, such as # of steps, yield, solvent, reagents, etc.

They will bring up any reactions they find in peer-reviewed literature and patents, and provide links to the literature, or links to other related compounds.

5

Chemistry / Re: In the compound 'NH₃', why 'N' is in the left?

« on: 29/08/2018 18:31:38 »

If we split 'NH₃', we get 'N³⁻' and 'H³⁺' and in 'NH₃', N is more electronegative than H. So 'H' should be in the left and the formula should be'H₃N' as in 'NaCl' where 'Cl' is more electronegative than 'Na' So could you explain why this structure in 'NH₃'?

It actually splits into N^3– and 3 H⁺, but you're right that the convention for writing chemical formulae often puts the least electronegative element first, like H₂O or HCl. You will occasionally see ammonia written out as H₃N, but NH₃ is more common--probably in analogy to CH₄...

Ultimately it means the same thing whichever way it is written.

6

Technology / Re: How do batteries work?

« on: 28/08/2018 02:23:30 »

Essentially any substance can be oxidized or reduced, provided a sufficiently strong oxidizing agent or reducing agent.

Sugar doesn't conduct electricity, so it would be difficult to make an electrode out of sugar, but solutions of sugar can be either oxidized or reduced when exposed to a conductive electrode. The reaction at the other electrode could be reduction of oxygen (an oxygen-sugar "battery" is more properly called a fuel cell), or reduction of silver(I) ions. I know that silver(I) can oxidize sugar because that's how the Tollens test/Tollens reaction works:

7

Chemistry / Re: Are there molecules inside the atom?

« on: 12/08/2018 18:39:11 »

molecule + molecule = bigger molecule (if covalently bonded) or adduct (if only bound by intermolecular forces or "dative bonds")

8

Chemistry / Re: How to calculate the maximum charge of an atom or a molecule?

« on: 10/08/2018 12:55:11 »

One must use a periodic table and some rules of thumb (some elements can have multiple oxidation states/charges).

In general, elements in the left 2/3 of the periodic table will lose electrons and form positively charged ions (formal oxidation states), while in the right 1/3 they will gain electrons and form negatively charged ions (formal oxidation states). The number of electrons lost or gained can be determined based on how far they are from the edges of the periodic table.

The first column (H, Li, Na, K, etc.) will lose 1 electron.
The second column (Be, Mg, Ca, etc.) will lose 2 electrons.
The transition metals are tricky, and will not be discussed here, but it is typically a safe bet that they lose electrons.
The next column (B, Al, Ga, etc.) will lose 3 electrons.
The next column (C, Si, Ge, etc.) will lose or gain 4 electrons.
The next column (N, P, As, etc.) will gain 3 electrons.
The next column (O, S, Se, etc.) will gain 2 electrons.
The next column (F, Cl, Br, etc.) will gain 1 electron.
The last column (He, Ne, Ar, etc. won't gain or lose any electrons.
The f block (those two rows often shown separated at the bottom) is also tricky, but it's typically a safe bet that they lose 3 electrons.

Occasionally H gains 1 electron (some people even place it in the second to last column, over F on the periodic table)
Also, Cl, Br and I can sometimes lose 1 electron.

9

Physics, Astronomy & Cosmology / Re: Quantum Locking and the Earth's Magnetic Field?

« on: 09/08/2018 20:29:25 »

Welcome to the forum!

There are a fair number of members who have at one point or another used the forum to test out ideas for sci-fi. This can get somewhat tricky because different members have different tolerances for the "fi" part. This subforum "Physics, Astronomy & Cosmology" is reserved for topics that fall within "commonly accepted science." This doesn't necessarily preclude addressing purely hypothetical questions, but once the hypothetical scenarios become extreme, addressing the questions with "commonly accepted science" is difficult. In these cases, the "Just Chat" and "New Theories" sections would be appropriate. Don't worry if a moderator moves one of your threads to these sections.

And now to the topic of the question:
I suspect you would need to invoke some pretty extreme circumstances to levitate islands off the surface of the Earth with a magnet at the core. There are a few things to consider:
• What is the island made of? Some materials are attracted to magnets, and some are repelled, while some resist moving across magnetic field lines. (I believe this last one is what you are after, given the term "quantum locking"--to do this effectively, the island would need to be superconductive, which is theoretically possible to achieve at room temperature, but so far the hottest temperatures that superconductors work at are around liquid nitrogen temperatures.

If quantum locking is indeed your goal, then the current state of Earth's magnetic field has a major problem: This effect (as demonstrated in the video) has to do with the fact that the strength of the magnetic field changes with the distance from the magnet--the strength of the effect has more to do with how much the field strength changes over distance (the gradient) than how strong the field is at any particular point (though the highest gradients will be found very close to very strong magnets). Even if the strength of the magnet at the Earth's core were increased a million times, the gradient of the magnetic field at the surface of the Earth would be quite small because the surface is so far away. (note that in the video the amazing world record distance between the very strong magnet and the superconductor was measured in tens of millimeters--and you are asking if it can be done at thousands of kilometers.

Bonus questions:
Increasing the strength of the magnetic field to have the necessary gradient at the surface is likely to do several (very bad) things. Stuff that is paramagnetic would be pulled into the field, and stuff that is diamagnetic would be repelled. Depending on how strong field is, this could cause the composition of the crust to be very different from what it is now. If it is VERY strong, then it could potentially change how electrons behave, which could mess up how chemistry works (and would certainly mess up anything that involves electricity), and might even make light do odd things...

No idea how such a thing could be done (if it is even possible).

10

Physiology & Medicine / Re: Could someone get dopesick from fentanyl administration in a clinical setting?

« on: 09/08/2018 18:09:38 »

I have no first-hand experience with "dopesickness," but my theoretical understanding suggests that there might be two cases that should be distinguished, and I will use alcohol as an example because I am familiar with that first hand (and I expect many others are as well):
• There is the equivalent of a hangover, which can certainly occur after a single use, and despite being unpleasant is fairly short in duration.
• And then there are the DTs (which I have not experienced myself, but have observed their effects in others), which is an extreme case of withdrawal by an alcohol-dependent person--this can lead to hallucinations and seizures and is a long, painful and dangerous process.

11

Question of the Week / Re: QotW - 18.08.05 - Who counted all the stars in the universe?

« on: 09/08/2018 15:35:52 »

Nobody has counted all the stars (just as no one has counted all the grains of sand on the Earth). Various people have made estimates of the number of stars, and their educated guesses vary by a few orders of magnitude based on their definitions of "star," what assumptions they make, and what data they base their guesses on.

For instance, one could use a powerful telescope to look at a small fraction of the sky and actually count the number of stars that are visible there, and then (assuming that there is nothing special about that particular portion of the sky) divide that number by the fraction of the sky that it is (this will make the number bigger--for instance if I counted 200000 stars in 1/1000000000000 of the sky, then I would estimate that the observable universe contains 200000*1000000000000 stars).

Or one could use data collected on many stars to say that the average brightness of a star is X. Then one could measure the brightness of a galaxy that is a known distance away, and use that to estimate how many stars are in that galaxy. Then, assuming that that galaxy is representative, one can multiply by how many galaxies there are in the observable universe (likely using an approach to galaxy counting that is similar to the star counting described above).

Or one could do the same thing as the last way, but instead define how much a star weighs, and determine the mass of a galaxy...

These last two approaches both assume that galaxies are roughly the same (poor assumption, but easily corrected with a more complex model) and that most stars are in galaxies (a reasonable assumption, but still can cause significant errors).

Regarding definitions of what counts as a star... there is some ambiguity at the low end of the mass scale, on the spectrum of enormous planets < brown dwarves < red dwarves, and there is also some ambiguity on the large (or just dense) end: black holes, neutron stars, quasars, pulsars, quark stars?

EDIT: Oops, crossed with alan!

12

Physiology & Medicine / Re: Could someone get dopesick from fentanyl administration in a clinical setting?

« on: 09/08/2018 02:21:55 »

As far as I understand it, the mechanism of action for fentanyl is exactly the same as morphine. Same receptors, same agonism, just much higher binding constant.

13

Physiology & Medicine / Re: Could someone get dopesick from fentanyl administration in a clinical setting?

« on: 08/08/2018 20:05:41 »

A few points:

• Fentanyl is a very powerful opiate, and comes with all of the same side effects and inherent* risks whether administered by a professional in a hospital setting, or a druggie on the street (*by inherent, I mean risks due to the compound itself, of course there are issues with drug purity, dose control, and having antidotes/extra care on hand if complications arise, all of which make administration in a hospital safer than on the street).
• I think it is unlikely that a single dose would elicit withdrawal symptoms in a drug-naive person. However, an addict or recovering (recovered) addict could certainly experience withdrawal symptoms after a single dose. Some of this could be psychological effects, and some is physiological.
• "Crack" is not heroin with cocaine in it... Crack is the street name for freebase cocaine (powder cocaine is the hydrochloride salt). Neither of these compounds is similar at all to heroin--not in terms of structure, effect, mechanism of action. I'm sure there is a term for a mixture containing heroin and cocaine, but it's not "crack."

14

Technology / Re: How do batteries work?

« on: 07/08/2018 17:51:39 »

I still don't understand fully.

So both metals are neutral, but have tendency to release or gain electrons.

While it is possible to use two neutral metals with wildly different electronegativities (like aluminum and palladium), this is not always the case (see my previous post in this thread).

When connected together, their pairing tendency moves electrons from one to the other.

For the electrons to move, we need to provide a path, which we do via? What are the necessary characteristics of that path? Doesn't simple water do?

A wire provides the path for electrons to move. Water (or other highly polar liquids, or ionomers etc.) allow ions to move.

When electrons move, they generate positive and negative charged metals that create a potential difference.

What happens as the electrons move apart from charging the metals? So that the battery capacity drops yet the voltage stays the same?

If ions were not allowed to flow then yes, the there might be a very brief spike in current when the terminals are connected by a wire, but the voltage would drop to zero when the batteries internal electric field cancels out the inherent electron affinities of the different metals (and/or ions). But, when ions are able to move within the battery, their motion will keep the internal electric field very small (zero internal field, for perfect ion mobility), allowing the voltage of the battery to remain constant until one end runs out of electrons to give, or the other end runs out of space to accept electrons, or there are no more mobile ions. (to first approximation--the voltage will actually decrease slightly as one or more of the limits is approached, rather than suddenly dropping from 100% to 0%--but this is a complication you can ignore until you feel more comfortable with the "ideal" case. When ready for this complication, you can read about it here: https://en.wikipedia.org/wiki/Nernst_equation)

Very interesting.

So to sum up the principles:
1) the electromotive force for a battery to work is the electronegativity difference of two materials, which we can call them primary.
2) it is also needed to have a wire to allow electrons to transfer and produce work
3) it is also needed to have a SECONDARY connection between the materials AND a pool of positive and negative ions. This is because we need to prevent charging of the primary materials as their electrons move. If this charging is not prevented through the use of a third material's ions in a solution that connects the primary materials, the battery simply would stop to work.
4) the capacity of the battery drops as the battery is in use and the electrons flow from one primary material to the other. The capacity depends on the amount of materials that are contained in the electron donator material and the positive holes/gaps in the electron acceptor material.
5) the flow of the third material's ions in the solution which bridges both the primary materials, does not affect the electronegativity differential of the primary materials. This is only affected by the electrons available in the donator and the gaps available in the acceptor. The solution bridge's ipns only prevent build up of macroscopic charge of the primary materials that would oppose the electrons flow.
6) I suppose we need to supply the adequate amount of ionic solution so that there's protection from static charge build up throughout the life of the battery.

Is the above a comprehensive summary of battery operation?

Yes, that's a reasonable summary.

15

Technology / Re: How do batteries work?

« on: 26/07/2018 15:23:24 »

I still don't understand fully.

So both metals are neutral, but have tendency to release or gain electrons.

While it is possible to use two neutral metals with wildly different electronegativities (like aluminum and palladium), this is not always the case (see my previous post in this thread).

When connected together, their pairing tendency moves electrons from one to the other.

For the electrons to move, we need to provide a path, which we do via? What are the necessary characteristics of that path? Doesn't simple water do?

A wire provides the path for electrons to move. Water (or other highly polar liquids, or ionomers etc.) allow ions to move.

When electrons move, they generate positive and negative charged metals that create a potential difference.

What happens as the electrons move apart from charging the metals? So that the battery capacity drops yet the voltage stays the same?

If ions were not allowed to flow then yes, the there might be a very brief spike in current when the terminals are connected by a wire, but the voltage would drop to zero when the batteries internal electric field cancels out the inherent electron affinities of the different metals (and/or ions). But, when ions are able to move within the battery, their motion will keep the internal electric field very small (zero internal field, for perfect ion mobility), allowing the voltage of the battery to remain constant until one end runs out of electrons to give, or the other end runs out of space to accept electrons, or there are no more mobile ions. (to first approximation--the voltage will actually decrease slightly as one or more of the limits is approached, rather than suddenly dropping from 100% to 0%--but this is a complication you can ignore until you feel more comfortable with the "ideal" case. When ready for this complication, you can read about it here: https://en.wikipedia.org/wiki/Nernst_equation)

16

General Science / Re: Is zero an even number, odd number, or neither?

« on: 23/07/2018 17:47:07 »

0 is most definitely an integer. It is not a positive integer (nor is it negative), but it is nonetheless an integer (and an even integer at that!)

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Physics, Astronomy & Cosmology / Re: How does a fuel cell work and what is its efficiency?

« on: 20/07/2018 20:13:23 »

Would the following description be accurate?

We have two plates of catalyst divided by water. The outer side of one plate is exposed to atmospheric oxygen which converts it to oxygen ion. The outer side of the other plate is exposed to hydrogen that we supply and it converts it to protons. Obviously there's potential difference generated between the two plates.

Protons and oxygen are somehow diffused to the middle common space between the plates and they react to form water.

1) how are protons and oxygen ions diffused?
2) what's the purpose of the middle space?

Yes, that's a reasonable description.
1) If the space between the plates is filled with a liquid like water, then protons and (hydr)oxide ions are dissolved in the liquid as mobile ions, and are free to migrate/diffuse. If the space is filled with a solid, then it needs to be a special type of solid that is permeable to the ions.
2) the gap is needed to prevent short circuit--the electrons coming from the hydrogen need to pass through the external load  on their way to the oxygen to do useful work--otherwise you just have a fire.

18

Chemistry / Re: Can a Co-solvent disrupt solvation process?

« on: 20/07/2018 18:02:03 »

Can addition of a small amount of additive solvent reduce the solubility of a compound below that found in pure solvent?
Yes, absolutely! In these cases the additive can be called an "anti-solvent." I take advantage of this phenomenon fairly frequently for crystallizations.

For example, I can dissolve a polar compound in a polar solvent such as dichloromethane, and then by slowly* adding a non-polar solvent such as pentane, I can decrease the solubility of the solute to the point where the solution is saturated, and then even further to promote precipitation (crystallization) of the solute.

As far as the underlying reason for this: in most cases one has a polar (or even ionic) substance dissolved in a polar (high dielectric) solvent. By adding a nonpolar (low dielectric) liquid that is miscible with the polar solvent, reducing the effective polarity (dielectric). There are also some cases, though in which a more polar solvent can be the antisolvent. For instance, there are many organic compounds that are quite soluble in acetone (or ethanol), but hardly soluble in water. These compounds can be forced out of solution by adding water.

There are probably other cases in which there are more subtle effects involved (like pi stacking), but I think polarity is the dominant driver of most of these examples.

* By slow addition, I mean, over the course of hours, days, or even weeks. The more slowly the change occurs, the bigger and better the crystals can be (which is important for x-ray crystallography). I don't stand there and add the solvents over this whole time period, but usually can set up a system so that the antisolvent can slowly diffuse into the solution. When the antisolvent is less dense than the solution, one can very gently layer it on top of the solution, while trying not to mix it--and then just wait for entropy to take over and mix them. Or when the antisolvent has a higher vapor pressure than the solution, one can place an open container of the antisolvent and an open container of the solution in a sealed chamber together, and let the vapors of the antisolvent condense into the solution, precipitating the solute very, very slowly.

19

General Science / Re: Is zero an even number, odd number, or neither?

« on: 20/07/2018 16:28:13 »

Precisely what alancalverd said.

20

Chemistry / Re: What is the difference between cationic and anionic water?

« on: 20/07/2018 16:25:42 »

I believe that bored chemist's meaning is that the water itself is not ionic. By definition, water is H₂O, a neutral compound. Solutions that are primarily water, but also contain dissolved ions, are not water, they are aqueous solutions of salts (ie the bulk properties, like density, viscosity, index of refraction, composition, conductivity, vapor pressure etc. of a 2% salt/water solution are quite distinct from the properties of pure water, and will also differ from the properties of aqueous solutions of different concentrations, or containing different solutes). On the molecular level, saltwater is essentially just a mixture of neutral water molecules and charged ions (there is some interaction between the two, so the water molecules in salt water are slightly different from water molecules in pure water, but still not anything that could really be considered ionic water.)

So based on bulk properties, saltwater is not the same as water, and shouldn't be referred to as water (from a chemists, biologists or engineers perspective--a cartographer may beg to differ), and on a molecular level, water molecules remain neutral no matter what is dissolved therein. Thus, either on a bulk or molecular level saltwater cannot be considered ionic water.