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Solvation

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Teacher/Instructor Kendal Orenstein
Kendal Orenstein

Rutger's University
M.Ed., Columbia Teachers College

Kendal founded an academic coaching company in Washington D.C. and teaches in local area schools. In her spare time she loves to explore new places.

Solvation, also called dissolution, is the process of surrounding solute with solvent. It involves evening out a concentration gradient and evenly distributing the solute within the solvent.

Alright. Let's talk about solvation. Solvation is the process the process sorrounding solute particles with the solvent. So when we are dealing with solutions the solvation actually is what's actually happening within the solution. So we know that the universal solvent is water and we're dealing with water as a solvent. We're going to call that hydration. So you might hear that as well.

Alright. So the phrase like dissolves like, what does that mean? It might be something that your Chemistry teacher might have talked about in class. That actually means, we're dealing with polarity. So we're going to talk about water as a univ- because it's a universal solvent.

Water is a polar substance. Meaning that it has a negative end and a positive end. And so, we want to, anything that's polar has a charge, can dissolve within water. So when we're taking something that's ionic, we know ionic compounds are held together through electrostatic forces and they actually do have positive and negative ions within them, that's what makes the ionic compounds. So when you drop it into water, what happens? Well, these the ions are actually going to separate from themselves and they're going to be surrounded by the water particles. So that oxygen is negatively charged, they're going to surround, they kind of like attack this positive cation and that this is actually the solvation process. And the negative ones are going to be surrounded by the hydrogen. So the more that they're actually like pulling off and actually going away, the more the ions you're exposing and eventually all these will be exposed in water making the whole thing dissolved. Okay? The same thing happens within a molecular solution but you have to make sure the molecular solution is a polar substance. If it's non-polar, this actually won't be able to happen. And what happens is this is sugar, this is table sugar and the table sugar has oxygen and hydrogen bound together. And we know that hydrogen bound together we know will create hydrogen bonding. And so when water comes close to it, this actually will, it will surround it here and here. All over the place. You'll see this bond or this attraction for water with sugar. So when the sugar separates from itself, each sugar molecule separates from itself, water will actually surround it making it dissolvable or dissolve in the solution. So this is the process of solvation. Okay. It's only polar molecules can do this, do this, it's non-polar. they don't have water is not attracted to it at all. So it's not going to surround it at all, so it's not going to dissolve. So that's the idea of the like versus like, sorry, like dissolves like means.

So what kind of factors affect solubility rate? Well, meaning how fast can it dissolve? So if we have the more surface area exposure that this compound has to the water or whatever it's being dissolved in, but they will obviously dissolve faster. So if you think about like a sugar cube versus granular sugar, the sugar cube will take a little bit longer to dissolve than the granular sugar which will be much quicker because it's more exposed. Stirring or agitating it obviously that's why you're - when you're thinking about dissolving something you stir it, that makes sense. That's actually making it more exposed as well. And then heating. When you heat something up, that creates more kinetic energy and things are moving around much more. So, you're able to dissolve this solvation processes if you are able to at a quicker rate.

I come across words like saturated, sorry. Unsaturated, saturated and supersaturated, when something, only a certain amount of substance is able to dissolve in, let's say 100 grams of water. So if it's not to that point, there's actually a point. It's called saturation point and if you get if you don't get there, if you can still do continous to dissolve more sugar or whatever we're talking about in that water, that solution is what we're going to call unsaturated. Meaning you can continously add more solute into the solvent, that solution until you get to the saturation point and once you hit the saturation point, it's going to be saturated. Meaning you can't add any more in there. And supersaturated, what's that? That means like if you heat up the substance the more, the hotter the substance is, the more it's able to dissolve something. So if you heat up the substance and then put in like a certain amount of sugar and then cool the substance back down, that certain amount of sugar is actually too much that cool temperature, but it will stay in solution because you'd have originally put it there. And if you agitate it just a bit, it will start crystallizing out and that's how like things like rock candy is formed or things like that. It's from supersaturated solutions.

And gas solutions are actually a little bit unique too. Let's think about soda as an example. Soda is a typical like gaseous solution within a liquid. And so we talk, let's talk about pressure. So if you have a two litre container of soda, how are you going to make sure that the gas doesn't escape from that soda and make it a non-gaseous solution. Well, you probably want to keep it cold. The colder a solution is, the less movement those gas particles will have to escape. So the colder a solution is the more it will stay in solution and not only that. The more pressure you have in that solution the more those gas particles will want to stay in that liquid. they're not going to escape. So those kind of things are unique within gases.

So the more, actually, the higher the temperature of the gas is, the solution with the gas is, the worse it is for that gaseous solution. It will actually like not be able to dissolve as much. So it's kind of the opposite as you would think to other types of solutions. So it is unique in that way.

So these are the properties and the reasons things dissolve in other solutions and it's called solvation.