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Chromotron t1_iyd79iq wrote

Reply to comment by ialsoagree in ELI5: Why does stuff dissolve in hot water more? by samuelma

Are you seriously saying that "hydrogen bonding" is not "bonding""? Because that is clearly silly.

And yes, they said the new bonds (the hydrogen ones, duh!) release energy; after more(!) energy was used to break ionic bonds.

You are just trying to be pedantic and fail at it.

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ialsoagree t1_iyd7zq3 wrote

I'm saying it's not "bonding to a molecule" if you disagree you need to take introductory chemistry.

Further, I just want to point out, hydrogen bonding only applies to ionic substances being dissolved in specific solvents. So many things dissolve without hydrogen bonding at all.

You clearly don't understand the basics of chemistry.

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Aurigae54 t1_iydggw9 wrote

Thats not true. Hydrogen bonding is an intermolecular force of attraction, as in between two molecules, and it certainly doesn't only apply to ionic substances being dissolved. The reason why water is a liquid at room temperature is because of hydrogen bonding between the positive hydrogen ends of one water molecule being attracted to the negative end of a second water molecule.

I think the point you were getting at was intramolecular vs intermolecular forces of attraction, and that in general intramolecular forces are considered to be true bonds, as they hold the atoms in different molecules and compounds together whereas intermolecular forces, not being nearly as strong as intra, are generally demoted to just being weak attractive forces, with hydrogen bonding being confusingly named as its not even a true bond by these metrics. This whole thread seems pretty semantic, 'bond' is just a strong word to describe an attractive force, at the end of the day and at its core a triple covalent bond is not that different from dispersion forces, they are just two ends of a spectrum representing how little/how much energy you need to break an attraction.

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ialsoagree t1_iydj3qr wrote

You said "that's not true" but then discussed a bunch of stuff I never mentioned. I never mentioned whether or not hydrogen bonding only applies to dissolving substances. I never mentioned water being a liquid at room temperature.

But I will address this:

>they are just two ends of a spectrum representing how little/how much energy you need to break an attraction.

At a physical level I agree with you. But not at a categorical level. These things are categorically distinct when we talk about them because of the size of disparity in energy required.

Let a cup of salt water sit and salt will spontaneously crystallize out of the water within hours. Just through Brownian motion.

Stable molecules could take billions of years to change their structure, or longer. This is why we categorize "water" as it's own molecule, and "salt" as it's own molecule, but we don't categorize "salt water" as a molecule - we categorize it as a solution of 2 molecules.

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Chromotron t1_iyd8gzo wrote

Well, I will leave my expertise of chemistry to the other readers (and my post history), but you clearly can only do insults (and down-votes, it seems; surely a sign of a healthy adult scientific discussion!).

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ialsoagree t1_iydb6tk wrote

>you clearly can only do insults

Says person who referred to my posts as "pedantic" because they corrected incorrect statements.

The only difference is - all of my posts have contained content that directly supports my position by describing how chemistry actually works. This post of yours doesn't, it JUST serves to insult me.

>and down-votes

Yes, because you haven't down voted any of my posts, right? *Eye roll*

If you want to have a "healthy adult scientific discussion" I'm happy to do that.

But saying "hydrogen bonding is a form of bonding with molecules" isn't an adult scientific discussion. It's a blatant misrepresentation of actual chemistry. A hydrogen bond - as I stated in my very first post - is a dipole-dipole interaction. It's an inter-molecular force (a force between two separate molecules, not a bond) similar to Van Der Waals forces but many magnitudes greater in strength.

Further, hydrogen bonding doesn't even apply to the way many things dissolve. So even if we could ignore chemistry and say that hydrogen bonding is a form of bonding to a molecule - which it's decidedly not - that STILL wouldn't make the post I replied to correct, because it only applies to a subset of things that dissolve.

Organic molecules, for example, can dissolve through Van Der Waals forces or/specifically London dispersion forces.

Something being dissolved can be endo or exothermic, there's no hard and fast rule about whether dissolving something will heat or cool a liquid. Saying it's one way or another just isn't accurate, it depends entirely on what you're dissolving.

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Chromotron t1_iydcjkw wrote

> Something being dissolved can be endo or exothermic, there's no hard and fast rule about whether dissolving something will heat or cool a liquid. Saying it's one way or another just isn't accurate, it depends entirely on what you're dissolving.

Look, you get hinged on this again, yet the original post never said it is just one or another. It differentiated between the exothermic "reaction" of the formation of hydrogen bonds (or van-der-Waals forces or others, unmentioned ones) and the endothermic dissolution of the (often ionic, but also not explicitely mentioned) bonds in the solid. Those are two things, their sign is (almost always) pretty clear and opposite, and the heat/cold of dissolution comes from their (signed!) sum. Hence it can be either way, and this was mentioned in that post.

Yes, they left out some detail and might( have wrongly implied that the total is always negative, i.e. dissolution is endothermic, but this was not what you called out and this is ELI5, not a journal paper.

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ialsoagree t1_iydecbl wrote

>Yes, they left out some detail and might( have wrongly implied that the total is always negative, i.e. dissolution is endothermic, but this was not what you called out and this is ELI5, not a journal paper.

Sure, you could argue that his statement was specifically saying that hydrogen bonding - or any other force being used to maintain the solvation of the solute - is exothermic.

But my point remains that this isn't a bond between molecules, and that is an ELI5 level topic.

There is no point in chemistry where anyone would ever suggest that solvation involves molecules bonding. No chemistry teacher would ever say that hydrogen bonds, Van Der Waals forces, or any other intermolecular force is "bonding with the liquid molecules" or that "this creates new bonds."

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Chromotron t1_iydftjk wrote

Let me quote Wikipedia, but this is also in agreement with what I learned and sources are given there as well: '''The strength of chemical bonds varies considerably; there are "strong bonds" or "primary bonds" such as covalent, ionic and metallic bonds, and "weak bonds" or "secondary bonds" such as dipole–dipole interactions, the London dispersion force and hydrogen bonding.'''

So bonds are just that, bonds. Some are just stronger or more commonly encountered.

Also, dissolving salts involves their ionic bonds, so if we are pedantic, this part involves even more bonds. But I get some feeling that even ionic bonds are not "bonds" in your mind, only covalent ones?

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ialsoagree t1_iydhqgw wrote

I appreciate that wikipedia may describe it like this, but that doesn't make it an accurate description used in chemistry.

This paper, for example, specifically looks at the differences between chemical and hydrogen bonding (specifically by look at bond strength).

>But I get some feeling that even ionic bonds are not "bonds" in your mind, only covalent ones?

I'd argue that the distinction is more categorical than physical.

All chemical bonds are covalent bonds, there's just a disparity in how much the electrons are actually shared.

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