Types of Mixtures

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

Types of Mixtures Types of Mixtures

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    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!

    • This article is about types of mixtures.
    • First, we will define a mixture.
    • Then, we will look at homogeneous mixtures and their two special types: solutions and alloys.
    • Next, we will look at heterogeneous mixtures and their two special types: colloids and suspensions.
    • Then we will use our new skills to identify the type of mixture.
    • Lastly, we will learn about some different methods of separating mixtures.

    Two Types of Mixtures in Chemistry

    A 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:

    1. Homogeneous mixture
    2. Heterogeneous mixture

    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 Mixtures

    A 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:

    Types of Mixtures Homogeneous salt water StudySmarterFig.1-Different homogeneous salt water mixtures

    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 Mixtures

    In 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.

    Types of Mixtures Heterogeneous mixture StudySmarterFig.2-Different heterogeneous mixtures.

    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:

    1. Colloid.
    2. Suspension.

    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:

    • Sol: Solid particles in a liquid
      • Ex: Paints: pigment particles in water
    • Emulsion: Liquid particles in a liquid
      • Ex: Oil in water
    • Foam: Gas particles in liquid/solid
      • Ex: Soap bubbles
    • Aerosol: liquid/solid particles in a gas
      • Ex: Smoke: soot in carbon dioxide
    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.

    Types of Mixtures Particles sizes for different mixtures StudySmarterFig.3-Different sizes of particles for different mixture types

    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:

    Types of Mixtures The Tyndall Effect StudySmarterFig.4-The Tyndall effect.

    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 examples

    Now 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 mixtures

    Since 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.

    Name of MethodProcessUsed to separate
    FiltrationA filter paper is placed in a funnel, and the mixture is poured over it. The solid particles will be caught by the filter, while the liquid will pass throughLiquids from insoluble solid
    EvaporationThe mixture is heated, so the liquid is boiled offSoluble solids from a liquid
    DistillationThe mixture is boiled and then condensed. The different components will evaporate at different temperaturesTwo or more liquids that are miscible/mixable with different boiling points
    ChromatographyThe solution is spotted onto a silica gel plate, which is placed in a solvent. The solvent will carry the different components at different rates, separating themCompounds with similar properties, but different polarities.
    Separation funnelThe mixture is placed in a separation funnel, which is shaken/inverted several times until the liquids separateImmiscible liquids (have different densities)

    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

    • A 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.
    • A 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
    • A solution is a homogeneous mixture that is formed when a solute is dissolved in a solvent.
    • An alloy is a homogeneous mixture of a metal + another metal or nonmetal
    • In a heterogeneous mixture, the composition is not uniform and there are clear and distinct phases.
    • Colloids are a mixture where small, insoluble particles are suspended in another substance.
    • Suspensions are a mixture where large, insoluble particles are suspended in another substance, but will eventually settle
    • When light passes through a colloid/suspension, the particles deflect the light, causing it to scatter. This is called the Tyndall effect

    • There are several ways to separate mixtures such as filtration, evaporation, distillation, chromatography, and separation using a separation funnel

    Frequently Asked Questions about Types of Mixtures

    What are 5 examples of mixtures?

    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. 

    What are the 2 classifications for mixtures?

    The 2 classifications are homogeneous mixtures and heterogeneous mixtures.

    What is a homogeneous mixture?

    A homogeneous mixture is a mixture that is uniformly distributed.

    What is a heterogeneous mixture?

    A heterogeneous mixture is a mixture that isn’t uniformly distributed.

    What type of mixture is air?

    Air is a homogeneous mixture. 

    Test your knowledge with multiple choice flashcards

    _________ mixtures are uniform in composition.

    _________ mixtures are mixtures that aren’t uniform in composition.

    What are the differences between a mixture and a compound? Select all that apply

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