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Chromotron t1_iyd8gzo wrote

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

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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