A solution is a homogenous mixture that could be not just liquid but also a mix of solids. A solute is something you dissolve in something else; it’s what gets dissolved in solvent. A solvent is the thing that dissolves.
You can have liquids that dissolve in each other and are called miscible. Things that don’t dissolve are called immiscible. If you have 95% alcohol and 5% water, which one is the solvent or solute? When you have solutions like this, the one that is more is the solvent, so the alcohol in this case.
Let’s investigate the dissolving process. First you disperse a solute in the solvent. Interactions occur in between them and we also know that there is a variability to how soluble something is.
1. You have to separate solute molecules. Do you think they are going to naturally separate or have some sort of resistance?
2. There must be space between solvent molecules.
3. An interaction needs to be made.
#1 and #2 are Endergonic and Endothermic (requires energy). #3 is Exergonic and Exothermic.
If you compare energy requirements between 1/2 and 3, for the most part, things are going to be soluble if you think about how much energy it takes to do #1 and #2 versus #3.
“Hydration” is when water is combined with something else. When you’re dealing with other molecules it’s called Solvation.
When something is not soluble it means process #1 and #2 require more energy than #3. But sometimes things dissolve even if they shouldn’t. There’s 3 rules that don’t explain the whole picture. The reason for that is ENTROPY.
#4 Entropy – randomness or the tendency for things to get randomized – is an additional consideration.
Numbers 1 and 2 oppose dissolving while 3 and 4 prefer dissolving. Only 1, 2 and 3 determine whether something is an endergonic process or exergonic but you need to factor in entropy to know whether something will dissolve.
What dissolves in what? Like dissolves Like.
Two polar things will dissolve because of rule #3.
Two nonpolar things will dissolve due to entropy being the dominant factor.
Rate of dissolving (how fast)
Depends on Temperature, Stirring and Surface Area
Temperature. However this has barely any effect on ‘salts’ such as NaCl as they barely increase solubility by 5% if raised by 100 degrees.
1. Pressure (higher p = higher solubility) and 2. Temp (higher temp=less solubility) Remember how boiling water makes water dissolve.
Three types of Solutions
If a solution can still dissolve more solute, it’s unsaturated.
If a solution can’t dissolve anymore, then it’s called, saturated.
When there’s more solute than a saturated solution, that’s called super-saturation.
Interesting thing happens when you have sodium acetate that is totally saturated and you add MORE of it: