The dissolution of salt in water is a physical change. 1 It does not involve a change in the chemical composition of the salt or water molecules. Rather, it is a process in which the ionic bonds between the sodium and chloride ions in the salt are broken as they become surrounded by water molecules, resulting in the formation of a homogeneous solution.
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Key Takeaways: Is Salt Dissolving a Physical or Chemical Change?
- The dissolution of salt in water is a physical change, not a chemical change.
- Salt dissolving in water involves the physical dispersal of salt ions without any chemical reactions or changes in the chemical composition of the salt itself.
- The process of salt dissolving in water is reversible, and the dissolved salt can be recovered by evaporating the water.
Why is salt dissolving a physical change?
The dissolution of salt in water is generally considered a physical change rather than a chemical change. 2 This is because the chemical composition of the salt does not change during the process of dissolving.
In a physical change, the substance involved undergoes a change in its physical state or appearance, but its chemical composition remains the same. 3
When salt dissolves in water, the sodium ions (Na+) and chloride ions (Cl-) that make up the salt crystals separate and disperse throughout the water. 4 However, the chemical bonds between the sodium and chloride ions remain intact.
The dissolved salt can be recovered by evaporating the water, and the resulting salt crystals will have the same chemical composition as the original salt. 5
In contrast, a chemical change involves a rearrangement of atoms and a formation of new substances with different chemical properties.
For example, if the salt were to undergo a chemical change, it might react with another substance in the water to produce a different compound.
So, in the case of salt dissolving in water, it is considered a physical change because only the physical arrangement of the salt ions is altered, while their chemical identity remains the same.
Why is salt dissolving not a chemical change?
Salt dissolving in water is not a chemical change because the process does not involve a breaking or formation of chemical bonds between the sodium and chloride ions. It is a physical change because only the physical state and arrangement of the salt ions change as they disperse throughout the water.
When salt is added to water, the polar water molecules surround the charged ions, exerting attractive forces that overcome the forces holding the salt crystals together. 6
As a result, the salt crystals break apart, and the individual ions become surrounded by water molecules. The dissolved salt ions are evenly distributed throughout the water, forming a homogeneous solution.
(You can see this animation or a video given below for a better understanding of how salt is dissolved in water).
This process of dissolution is reversible, as the dissolved salt can be recovered by evaporating the water, leaving behind the original salt crystals.
The chemical composition of the salt remains the same throughout the dissolution process, as there is no change in the arrangement or identity of the atoms within the salt molecules.
In summary, salt dissolving in water is a physical change because it involves the dispersal of salt ions within water without any chemical reactions or changes in the chemical composition of the salt itself.
Further reading
Is Burning of a Candle a Physical or Chemical Change?
Is Burning of Paper a Physical or Chemical Change?
Is Melting a Physical or Chemical Change?
Is Burning a Physical or Chemical Change?
Is Frying (or Cooking) an Egg a Chemical Change?
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References
- Is Dissolving Salt in Water a Chemical Change or Physical Change? (2020, January 13). ThoughtCo. https://www.thoughtco.com/dissolving-salt-water-chemical-physical-change-608339
- Uen.org https://www.uen.org/lessonplan/view/2683
- Chemical Change vs. Physical Change. (2013, October 2). Chemistry LibreTexts. https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Fundamentals/Chemical_Change_vs._Physical_Change
- Water molecules and their interaction with salt | U.S. Geological Survey. (n.d.). Water Molecules and Their Interaction With Salt | U.S. Geological Survey. https://www.usgs.gov/media/images/water-molecules-and-their-interaction-salt
- Foundation, N. (2023, June 6). Separating sand and salt by filtering and evaporation. RSC Education. https://edu.rsc.org/experiments/separating-sand-and-salt-by-filtering-and-evaporation/386.article
- Dissolving and Back Again – American Chemical Society. (n.d.). American Chemical Society. https:///education/resources/k-8/inquiryinaction/fifth-grade/chapter-1-investigating-matter-at-the-particle-level/lesson-1-3–dissolving-and-back-again.html
