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Granted that saltwater is a commonplace substance, and understanding that it is a solution as opposed to a mixture or compound may seem nit-picky or uninteresting. But actually, comprehending this physical chemistry distinction is an achievement well worth grappling with for the purpose of accuracy and personal knowledge.
Saltwater is classified as a solution because it consists of salt, a solute distributed evenly in water, and a solvent. Furthermore, saltwater is also considered a homogeneous mixture because the composition and properties are consistent, chemical bonding has not occurred, and it can be mechanically separated.
In addition to defining saltwater as a solution in the realm of physical chemistry, this article will describe why it is a solution, how it is also a homogeneous mixture, and describe the process of combining salt and water. Finally, the mechanical solution reversal process will be examined.
What Is a Solution?
A solution can take the form of a gas, liquid, or solid and consist of more than one solute substance that dissolves in a solvent substance. The solvent is the majority of the mixture. Together, the solute(s) and the solvent create a homogeneous mixture with too microscopic particles to be seen. Additionally, a solution may be physically changed but has not been chemically transformed.
Why Is Saltwater a Solution?
Saltwater adheres to the definition of a solution because:
- It is a mixture in which a high salt concentration is dissolved in water and is uniformly or homogeneously distributed.
- Saltwater can be separated or broken down into compounds.
That being so, saltwater is in the liquid form. Water is the solvent, and salt is the solute that dissolves into the water. In addition to the liquid, solutions can be found in a gas or solid form or phase.
Physical Phases and Examples of Solutions
- Gas – air, natural gas, nitrogen
- Liquid – saltwater, blood, milk, rubbing alcohol
- Solid – alloy, ice
Saltwater Compounds, Elements, and Formulas
Moreover, both salt and water are formed by chemically combining the elements into a formula, as summarized by this table. The formulas or compounds are then physically combined to create the saltwater solution.
|Salt (solute)||Sodium (Na) and Chloride (Cl)||NaCl|
|Water (solvent)||Hydrogen (H) and Oxygen (O)||H2O|
Since one of the components is the universal solvent, water is further specified as an aqueous solution. In a saltwater solution, the particles are so small that one type of molecule is dissolved into another kind of molecule and spread evenly throughout the liquid. The particles cannot be seen, and they cannot settle out of the liquid.
The molecules remain chemically the same because the bonds have not been broken during dissolution. As a result, a physical method of separation can be used to re-create the salt and water compounds. A chemical change has not been made.
Saltwater as a Homogeneous Mixture
A solution consists of a homogeneous mixture of two or more substances in which one or more solutes are dissolved in a solvent. According to the components of physical chemistry, all homogeneous mixtures are solutions.
In contrast, a heterogeneous mixture contains at least two components that are not uniformly or evenly dispersed throughout the mixture and are identifiable as being different. For example, if salt and pepper are mixed together, the different salt granules and pepper flakes can be identified. The proportion of salt versus pepper may be different as well. Heterogeneous mixtures are not solutions.
Process of Combining Salt and Water to Form a Solution
Saltwater is a solution that breaks down salt into smaller pieces due to being mixed with water. When dissolved, the particles are so small that they cannot be seen. Saltwater, due to an intermolecular attraction, is more likely to dissolve within one another and is termed as miscible because the substances mix equally in all proportions.
If you would like to see the chemistry of solution formation on a microscopic level, view this short video, which is less than one minute long. The narrator describes how water is attracted to the positive and negative ions of salt and how dissolution occurs, and the solution is formed.
How Long Does It Take to Dissolve Saltwater?
The rate of dissolution of salt into water is affected by the collision that occurs between the solvent and the solute. It is influenced by stir speed, temperature, and the size of the salt particles.
To speed up the process, stir more rigorously, heat the mixture, and use smaller salt particles. Interestingly, heating up the mixture also affects the amount of salt that is dissolved as well as how quickly.
Solution Separation Process
The solution can be separated into its two compounds by mechanically capturing water condensation and salt residue in a distillation process. Other physical methods of separation may include filtration, crystallization, or evaporation.
Sea salt is known to be obtained by the evaporation of seawater via heat from the sun. The seawater is collected into a pond and processed through an evaporation technique that removes the liquid leaving only the sea salt for harvesting.
In this seven-minute video, a high school science instructor demonstrates the physical change of solubility. What’s interesting is that he also shows the change in physical state by removing the salt compound from the liquid without creating a chemical change.
A solution is within the physical chemistry field by definition because it pertains to the study of chemical systems. The formation of a solution, or the solution process, is a physical change, not a chemical transformation.
Specifically, the saltwater chemical elements combine to make compounds, and the compounds combine to create a homogeneous mixture or solution. In the end, water droplets can evaporate or be mechanically boiled to separate from the salt substance. Therefore, the solution can be ultimately separated because the chemical bond is not broken. Physical changes are made, but new substances are not created.
Although it can be difficult to determine if a chemical change has occurred when mixing solutions, there are multiple indicators to watch for that may take place. If the solution has changed color, temperature, or there is a gas forming, the solution is more likely a chemical change. For instance, common chemical reactions are burning wood or a rotting banana.
Detailed and extensive physical chemistry books, such as the Physical Chemistry: A Molecular Approach, describe the subject comprehensively.
Meanwhile, on the other end of the spectrum, the Chemistry Concepts Coloring Book contains, among other lessons, a visual of solutions and its relationship to the matter at the most basic level. Physical chemistry is a vast subject, with solutions being a small but integral part.
The concept of physical chemistry aids in understanding why saltwater is, in fact, a solution. By defining a solution and specifically using the compounds that form saltwater as an example, it is understood that a homogeneous mixture is created by physically combining the salt and water compounds uniformly, thus creating a solution. Solutions are always considered homogeneous mixtures.
In addition, a saltwater solution can, in turn, be separated by a physical method to return to compound substances.