How Do Substances Dissolve Others?

by Carson
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What happens when you mix salt and water? Well, the salt will seemingly completely disappear. But in fact, this is the process of solvation. How does a chemical dissolve another? Let’s find out.

How Does Solvation Work?

Solvation is the interaction between a solute and a solvent so that the solvent breaks up the molecules of the solute. Take table salt and water for example. You probably know that a table salt molecule consists of a sodium atom and a chlorine atom, and a water molecule comprises 2 hydrogen atoms and 1 oxygen atom. These atoms exchange electrons, so sodium and hydrogen ions are positive with missing electrons, while chlorine and oxygen ions are negative with extra electrons.

When positive and negative charges come together, they will attract each other. Therefore, each of the ions will try to pull others with a negative charge towards itself. But if the charge is evenly distributed, the atomic bonds of the solvent overpower that of the solute, breaking the atoms in the solute apart into ions and clinging them onto the molecules of the solvent.

An illustration for a positive ion attracted by some negative ions
Image created using Canva

Keep in mind that this mechanism is for polar solvents. Polar solvents can only dissolve polar solutes, while non-polar solvents can dissolve non-polar solutes.

Why Do Solutions Become Saturated?

If a fixed amount of solvent has dissolved a sufficient amount of solute, the solution won’t be able to dissolve more solute anymore. This is when the solution becomes saturated.

Each time a molecule from the solute is dissolved, some molecules from the solvent must be used to retain it. Therefore, as more solute is added to the solution, all molecules from the solvent will eventually be used up, rendering it unable to dissolve anything further.

It’s natural to ask how much solute can a solvent dissolve. It depends on a few factors: pressure, temperature, the relationships between the solvent and solute, and so on. Keep in mind that some factors, like high temperature, are usually positive factors. Others, like the inability for a small amount of molecules to attract the ions from the solute, are negative factors.

What Affects the Rate of Dissolving?

How to speed up the process of dissolving? You should make the molecules collide more often in the solution. Firstly, you can stir the solution to speed up the movement of the molecules, thus making it attracted to the ions of the solute faster. If you warm the solution up, it also achieves the same thing.

How to Separate the Solute from the Solution?

After the solute is completely dissolved, you can’t separate the solute and solvent by methods like filtration. Instead, you have to heat the solvent so that it evaporates. That way, if the boiling point of the solute is higher than that of the solvent, the solute will remain solid/liquid, while the solvent will evaporate away. After that, you can condense the solvent and make it liquid again. This is distillation, one of the ways to purify water.

Conclusion

After reading this article, you should’ve learned a bit about how substances dissolve others in a solvation process. If you think crucial points have been missed in this article, please leave your opinions in the comments below. Moreover, to learn more, feel free to visit the websites mentioned in the references below.

References and Credits

  1. (n.d.). Why Does Water Dissolve Salt? Retrieved November 13, 2021, from https://www.middleschoolchemistry.com/lessonplans/chapter5/lesson3
  2. (n.d.). Chemistry: How and Why Do Things Dissolve? – Infoplease. Retrieved November 13, 2021, from https://www.infoplease.com/math-science/chemistry/chemistry-how-and-why-do-things-dissolve
  3. (2021, June 17). 13.2: Saturated Solutions and Solubility – Chemistry LibreTexts. Retrieved November 13, 2021, from https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Chemistry_-_The_Central_Science_(Brown_et_al.)/13%3A_Properties_of_Solutions/13.2%3A_Saturated_Solutions_and_Solubility
  4. (n.d.). Water Q&A: Why is water the “universal solvent”? Retrieved November 13, 2021, from https://www.usgs.gov/special-topic/water-science-school/science/water-qa-why-water-universal-solvent
  5. (2017, November 8). How Does Water Distillation Work? Retrieved November 13, 2021, from https://advancedwaterinc.com/water-distillation-work/

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