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If you’re planning a career as a chemist or just studying Chemistry or a general Science course, you will be taught how to distinguish a mixture from a solution. Deciding which is which can get confusing, however, because a solution is also a type of mixture.
Salad is a mixture. It is made up of more than one material, usually several chopped or torn vegetables with added toppings, all of which can be separated from each other after they are mixed. Unlike solutions, salads are made up of substances that do not react, chemically, with each other.
This article will discuss different types of mixtures and why some are easier to classify than others. It will hopefully clear up some confusion about mixtures and solutions and provide tips that make it easy to tell them apart.
What is a Mixture?
What is commonly called a “mixture,” is technically a heterogeneous mixture. The components of this combination are not of the same proportions and not evenly mixed. They can be separated by physical means.
What is a Solution
A Solution is a special kind of mixture, known as homogeneous. All of its components are of the same proportions and combined in a way that they cannot be filtered out or separated by physical means. A solution is made up of a solvent, often water, and a solute, such as salt, creating a liquid solution. It can also be a combination of gases and solids. The solution ends up as one phase, either liquid, solid or gas, even if the components were originally different phases, as in salt dissolved in water.
How to Tell If It’s a Mixture
Often you can identify a mixture simply by looking at it and seeing that you can easily remove any of its components. For example, if you don’t like carrots or broccoli in a salad you buy, you can simply take them out. The combination of beans and rice is another example of a mixture as is the coupling of peas and carrots. It’s not always this easy, though. For example, it may be hard to pick out short-grain rice, mixed with long-grain, but the combination is still a mixture that can be physically separated.
Some mixtures, even those harder to separate, are still not solutions because the substances put together don’t lose their original composition. Sand combined with water, for instance, remains a mixture, because the sand will settle to the bottom, rather than dissolve. Even concrete is a mixture, because it contains pebbles, sand and gravel.
How to Tell If It’s a Solution
This task is a bit more complicated. Generally, the parts mixed together to make a solution, the solute and the solvent, are dissolved into one liquid, gas or solid, and the original components can no longer be seen, with the naked eye, as separate. They also cannot be separated by mechanical means like filtering or breaking apart, once combined.
Examples of Mixtures (Heterogeneous)
· Concrete (gravel, sand, pebbles)
· Beans and rice
· Soda and ice cubes
· Cereal and milk
· Party mix – cereal, pretzels, nuts etc
· Air with clouds
· Vinegar and oil dressing
· Non-homogenized milk
Examples of Solutions
· Salt Water
· Homogenized milk
· Solution Alloys, such as brass and pewter
All Solutions are mixtures, but not all mixtures are solutions. Heterogeneous mixtures are usually called, simply, mixtures. Solution is the most common word used for a homogeneous mixture, even though not all homogeneous mixtures are solutions. For example, a jar of green M&M’s is a homogeneous mixture that does not involve a solute and a solvent being blended together. So, even though it’s homogeneous, it is not a solution.
Once you know the basic difference between the common use of the terms, Mixtures and Solutions, you’ll find a salad is easy to classify as a mixture. However, other common mixtures can be deceptive. For example, sodas like Coca Cola may appear to be solutions, and would be if carbon dioxide gas wasn’t added. According to Thought.Co chemistry expert Anne Marie Helmenstine, Ph.D., the carbon dioxide forms bubbles that are unevenly distributed within the drink. So she defines soda as a heterogeneous mixture.
Dr. Helmenstine explains another nuance—homogenization, which changes a heterogeneous mixture like natural milk, into a homogeneous one, i.e., homogenized milk. The process stabilizes the components that otherwise separate, with cream rising to the top.
As with most scientific subjects, you’ll find differing views among experts. According to those reporting on Wikipedia, an alloy can be either a solid solution, composed of metals, having crystals or grains of the same composition. Or, alloys can also be mixtures of two or more solutions….” According to lumen: Boundless Chemistry, “Alloys can be further classified as homogeneous (consisting of a single phase), heterogeneous (consisting of two or more phases), or intermetallic (where there is no distinct boundary between phases).” Dr. Helmenstein, however, defines all alloys as homogeneous solutions.
What about salt water and sugar dissolved in water? Educators also seem conflicted about these two mixtures. Some sources say salt water is a heterogeneous mixture because it can be separated by distillation or evaporation, while others say it’s a solution, since it can’t be physically separated once mixed. The same is true for sugar dissolved in water. Generally, to be a heterogeneous mixture, or a simple mixture, you must be able to manually separate or filter the components.
Interestingly, in another article on Thought.Co, Dr. Helmenstein says that salt water and sugar water are not the same kind of mixtures. She explains that salt water is the result of a chemical reaction between the salt and the water, creating an ionic compound. However, sugar dissolved in water, she says, creates a covalent compound and does not involve a chemical change.
Another Type of Mixture
An Australian school experiment addresses the two types of mixtures discussed so far and also includes a third—suspension. The example used is dirty water, which may also contain salt. Students identify the different types of mixtures to help determine what processes might need to be performed with surface water before it is suitable for drinking. This water is found in lakes or streams and contains organic matter, such as fallen leaves, and rain-event run-off, containing other contaminants.
In the experiment, students add and mix different substances to three separate glass containers, each containing a half cup of water. The substances are:
1. A teaspoon of dirt
2. A teaspoon of salt
3. A pea-sized piece of clay
Students can see that the first glass contains a mixture because the dirt settles quickly to the bottom of the glass. They then shine a light through glasses 2 and 3 and find that the container with salt water is clear, while the one with the clay scatters the light because the clay takes time to settle. Number 3 is an example of a suspension mixture, while the salt mixture is a solution.
Summing It Up More Simply
For a general, 2-minute summary of the difference between mixtures and solutions, view this YouTube video.
Another video, which summarizes the basic differences between heterogeneous and homogeneous mixtures, is found at the end of this article:
A salad is clearly a heterogeneous mixture. It would be correct to simply call it a mixture, but incorrect to classify it as a solution, because it is a mixture that can be physically separated, and its parts do not chemically combine with each other, as in the case of solutions. If you want to be specific about the type of mixture you’re referring to, you should explain whether it is heterogeneous or homogeneous and whether or not it is a solution.
The understanding of suspensions and other mixtures helps water resource engineers know how to treat raw, surface water to make it suitable for drinking. Also biomedical engineers study solutions and mixtures to develop new medicines. To separate the liquid solution (diluted white vinegar for example) you use to wash your vegetables (which you should definitely do) before serving or storing a salad, a spinner like this Cuisinart Salad Spinner is recommended.