When you take a breath of fresh air, you aren't just breathing in oxygen. You are actually inhaling several gases, such as nitrogen and hydrogen. You can't actually see the different components, are they are blended together in a uniform mixture. Show Air isn't the only mixture we see in our daily lives, from the soap we use to wash our hands, to the blood pumping in our veins, and to the soil that feeds our plants. All around us, there are mixtures, and in this article, we will be learning all about them!
Two Types of Mixtures in ChemistryA mixture is a substance that is formed by combining two or more other substances. This process is a physical, not chemical change, so each component retains its original properties. There are two types of mixtures. These are:
The main difference between these two types is the distribution of the components within the mixture. Mixtures are different from compounds since compounds are formed chemically, while mixtures are formed physically. Also, mixtures can be made from both compounds and elements, while compounds can only be made from elements. Types of Mixtures: Homogeneous MixturesA homogeneous mixture is a mixture with a uniform composition (i.e. it only has one phase). A phase is a portion of a sample that has a uniform composition and characteristics One key point about homogeneous mixtures is that you can't tell where one part ends and another begins. A good example of this is saltwater. In a sample of saltwater, you cannot see the individual grains of salts that have been dissolved, you instead see a unified cloudy mixture. Another key point is that homogeneous mixtures have a uniform distribution, but not a set ratio, like in a compound. For example, in the compound NaCl, there is always 1 mole of Na per 1 mole of Cl. However, in the mixture of saltwater, there could be 3 mols of salt per 10 mol of water or 6 mols of salt per 12 mols of water. The ratio doesn't matter, as long as the dissolved salt ions are spread evenly. The mixture of salt water is a solution. A solution is a homogeneous mixture that is formed when a solute is dissolved in a solvent. Here is what that would look like in a solution: The salt ions are spread evenly. If you cut either sample in half, the distribution is the same. This is why these solutions are considered "uniform". One special type of homogeneous mixture is an alloy. An alloy is a homogeneous mixture of a metal + another metal or nonmetal Some examples of alloys are brass (copper + zinc) and steel (iron + carbon).Types of Mixtures: Heterogeneous MixturesIn a heterogeneous mixture, the composition is not uniform and there are clear and distinct phases. Oil and water do not mix. If you pour oil into a glass of water, the oil will float above it. Each of these is a clear phase, and we can easily tell them apart. All mixtures of immiscible (don't mix) liquids are heterogeneous. Heterogeneous particles are not distributed evenly, as shown below. The mixture of oil and water would look like the example on the right. If I cut both of these samples into several pieces, each piece would have a different composition, which is why they are heterogeneous. There are two special types of heterogeneous mixtures: Colloids are a mixture where small, insoluble particles are suspended in another substance. Depending on the state of the suspended particles and the substance they are suspended in, colloids can have different names:
Suspensions are a mixture where large, insoluble particles are suspended in another substance, but will eventually settle. An example of a suspension is flour in water. When it is initially stirred, the flour particles are suspended in the water. However, after some time passes, the flour will sink to the bottom. While colloids and suspensions may be similar to solutions, they are different. There are two main differences. The first is that colloids/suspensions have two phases, since the particles are insoluble, while solutions only have one phase since the particles are soluble. The second difference is the size of the particles, as shown below. The particles in a solution are individual molecules/ions, while they are much larger in colloids and suspensions. The size of these particles also affects how light interacts with them, called the Tyndall effect. When light passes through a colloid/suspension, the particles deflect the light, causing it to scatter. This is called the Tyndall effect. Here is what that looks like: Essentially, the light particles (photons) are bouncing off the particles in the colloid/suspension, so they are visible. However, the particles in a solution are not large enough to cause this effect, so the light isn't visible. Types of mixtures and their examplesNow that we have a good understanding of the different types of mixtures, let's try identifying them. What type of mixture are the following examples? a) air b) chocolate chip cookie c) sand in water d) bronze e) muddy water f) mud a) Air is a homogeneous mixture since it has a uniform composition, and you cannot distinguish the individual parts (nitrogen, oxygen, etc.) b) A chocolate chip cookie has two phases: The chocolate chips and the cookie. Since it has two distinct phases, it is a heterogeneous mixture. c) Sand cannot be dissolved in water. When it is initially mixed in, it will be suspended in the water, but will eventually settle. Because of this, it is a suspension/heterogeneous mixture. d) Bronze is a mixture of two metals: copper and ion. Since it only has one clear phase, it is an alloy/homogeneous mixture e) Muddy water is a mixture of water and mud. Since the mud doesn't dissolve in the water and its particles are large/will settle, it is a suspension/heterogeneous mixture. f) Mud is a mixture of compounds like silt, clay, or soil mixed in water. These compounds are not soluble in water and are instead in suspension, however, they will not settle. Because of this, it is a colloid/heterogeneous mixture. Separation of mixturesSince mixtures are the result of a physical combination, they can be separated through non-chemical (physical) means. Below is a table listing some common separation methods and when they can be used.
Depending on the mixture, multiple methods can be used. For example, a mixture of sand and water can be separated through evaporation or filtration, but filtration is often easier/faster. Types of Mixtures - Key takeaways
Some examples of mixtures are salt-water solutions, gel and foam colloids, fruit salad, and cereal in milk suspensions. Solutions are homogeneous mixtures, while colloids and suspensions are heterogeneous mixtures.
The 2 classifications are homogeneous mixtures and heterogeneous mixtures.
A homogeneous mixture is a mixture that is uniformly distributed.
A heterogeneous mixture is a mixture that isn’t uniformly distributed.
Air is a homogeneous mixture.
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_________ mixtures are uniform in composition.
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_________ mixtures are mixtures that aren’t uniform in composition.
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What are the differences between a mixture and a compound? Select all that apply
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A mixture is formed by a physical process, while compounds are formed chemically.
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What type of mixture is a solution and why?
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Solutions are homogeneous mixtures. This is because the dissolved particles are uniformly distributed and there is only one phase.
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True or False: In a mixture, each component retains its original properties
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Which of the following mixtures are heterogeneous? Select all that apply
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Which of the following mixtures are homogeneous? Select all that apply
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How do we tell a colloid and a solution apart?
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We use the Tyndall Effect. This occurs when light is shined through a colloid, leading to its particles scattering light when compared to a solution.
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What are some common techniques of separating mixtures?
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Some common techniques we use to separate mixtures are filtration, evaporation, chromatography, distillation, and separation using a separation funnel.
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True or False: Alloys are heterogeneous mixtures
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Rank the following in order of increasing particle size: Suspension, solution, colloid
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Solution>Colloid>Suspension
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A mixture is a substance that is formed by combining two or more other substances.
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Which of the following techniques would we most likely use to separate a suspension such as flour in water?
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What technique would you most likely use to separate a soluble solid from a liquid?
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What technique would you most likely use to separate two immiscible liquids?
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Which of the following is NOT a type of colloid?
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