Dissolving is generally considered a physical change. It involves the dispersion of solute particles in a solvent, resulting in a homogeneous mixture without any change in the chemical composition of the substances involved. 1 While some instances of dissolving may involve subsequent chemical reactions, the act of dissolving itself is primarily regarded as a physical change.
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Key Takeaways: Is Dissolving a Physical or Chemical change?
- Dissolving is considered a physical change because it does not alter the chemical composition of the substances involved.
- Dissolving involves the dispersion of solute particles in a solvent to form a homogeneous mixture.
- No new chemical substances are formed during the process of dissolving, and the original substances retain their chemical identities.
Why is dissolving a physical change?
Dissolving is considered a physical change because it does not alter the chemical composition or identity of the substance undergoing the process. Instead, it involves the dispersion of particles of a solid, liquid, or gas into a solvent to form a homogeneous mixture.
Let’s understand this with some examples.
Examples
Here are a few examples to illustrate why dissolving is a physical change:
- Salt dissolving in water: When you add salt to water and stir it, the salt particles disperse and become evenly distributed throughout the water, forming a solution. The chemical composition of both salt (sodium chloride) and water (H2O) remains unchanged. You can recover the salt by evaporating the water. 2
- Sugar dissolving in coffee: Similarly, when you add sugar to coffee and stir it, the sugar particles break apart and spread throughout the liquid, creating a sweetened coffee solution. The chemical composition of both sugar (sucrose) and coffee remains the same.
- Dissolving ink in a solvent: If you have ever accidentally spilled ink on a paper towel and watched it spread, you have witnessed the physical change of dissolution. The ink particles disperse into the paper towel fibers, altering the appearance and spreading the ink, but the chemical composition of the ink remains intact.
In all these cases, the dissolving process can be reversed, usually through evaporation or filtration, to recover the original substances. This reversibility further supports the notion that dissolving is a physical change rather than a chemical one.
Why is dissolving not a chemical change?
Dissolving is not considered a chemical change because it does not result in the formation of new chemical substances. It is a physical process in which a solute disperses uniformly in a solvent, forming a solution. The original chemical composition of the solute and solvent remains the same.
When a substance dissolves, its particles separate and become surrounded by the solvent molecules. This occurs due to the attractive forces between the solute and solvent particles. No new chemical bonds are formed or broken during the process of dissolving. The solute particles disperse throughout the solvent, creating a homogeneous mixture.
In contrast, a chemical change involves a rearrangement of atoms or molecules, resulting in the formation of new substances with different properties. 3 4
Examples of chemical changes include;
These processes involve breaking and forming chemical bonds, leading to a transformation at the molecular level.
In summary, dissolving is a physical process where substances mix together without undergoing a change in their chemical composition. The original substances retain their chemical identities, and no new substances are formed.
Further reading
Is Boiling Water a Physical or Chemical Change?
Is Water Freezing a Physical or Chemical Change?
Is Wood Burning a Physical or Chemical Change?
Is Melting Ice a Physical or Chemical Change?
Is Rusting a Physical or Chemical Change?
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References
- 3.3: The Dissolving Process. (2020, June 19). Chemistry LibreTexts. https://chem.libretexts.org/Courses/Brevard_College/CHE_104%3A_Principles_of_Chemistry_II/03%3A_Solutions_and_Colloids/3.03%3A_The_Dissolving_Process
- Uen.org https://www.uen.org/lessonplan/view/2683
- D. (n.d.). Chemical change Definition & Meaning | Dictionary.com. Chemical Change Definition & Meaning | Dictionary.com. https://www.dictionary.com/browse/chemical-change
- Changes in Matter: Physical vs. Chemical Changes. (n.d.). Changes in Matter: Physical Vs. Chemical Changes. https://education.nationalgeographic.org/resource/changes-matter-physical-vs-chemical-changes