A mixture is characterized because there are two or more substances or elements that are united, but not chemically combined, and because it is possible to separate them.

A homogeneous mixture is one in which its components are mixed in such a way that it is impossible to differentiate them with the naked eye, being distributed uniformly . This type of mixture is in one phase (state of matter) and is also known as a solution or dissolution. An example of a homogeneous mixture or solution is a cup of hot coffee.

In contrast, the elements of a heterogeneous mixture are distinguishable by sight and their distribution is not uniform . Heterogeneous mixtures have at least two distinct phases (solid and solid, for example). A bowl of cereal with milk is an example of a heterogeneous mixture.

Homogeneous mixture and heterogeneous mixture

What is a homogeneous mixture?

A homogeneous mixture is a mixture that is in a specific state of matter (in a phase), in which the elements that compose it are mixed uniformly and in such a way that it is not possible to differentiate them with the naked eye. This type of mixture is also known as a solution or dissolution .

The quality of being homogeneous implies that no matter where a sample of the mixture is taken from, the distribution of its components will remain uniform. That is, the particles that make up the mixture are distributed in the same way throughout the solution.

The components of a mixture are arranged in such a way that it is not possible to distinguish each of them with the naked eye. This means that in order to observe each component of a mixture, it is necessary to have some kind of apparatus (for example, a microscope).

Characteristics of a homogeneous mixture

• The mixture of its components is uniform.
• It is found in a single phase or state of matter.
• It is not possible to differentiate the substances that compose it with the naked eye.
• It is formed by one or more solutes and a solvent.
• It remains stable as long as the same conditions (temperature, pressure) are present.
• Solute and solvent are miscible, particularly in the liquid state.

Phases or states of matter in a homogeneous mixture

When the solute dissolves in the solvent, the homogeneous mixture has a single phase . When talking about mixtures, a phase is the state of matter in which its components are found, whether liquid, solid or gas.

Each phase that forms a state of matter maintains its properties and chemical composition under specific temperature and pressure conditions. If these conditions change, the phase changes, passing to a different state of matter. An example of this occurs when rock melts due to an increase in temperature

A homogeneous mixture or solution is composed of at least two substances that are present in different quantities in the same mixture: the solute and the solvent.

A solute is the substance that is present in the smallest proportion in a homogeneous mixture. It takes the form and characteristics of the solvent (since it dissolves in it) and has a higher boiling point than the latter. The most common phase in which it is found is the solid state (although it is also found in other states)

An example of a solute is ground coffee that is mixed with hot water to make a cup of coffee.

The other component of a homogeneous mixture or solution is the solvent , which is the substance that dissolves the solute. The solvent is found in greater proportion than the solute in a solution and determines which phase or state of matter it will be in. It is generally a liquid, and the solvent par excellence is water.

Properties of a homogeneous mixture

Homogeneous mixtures, such as solutions or dissolutions, have several properties. In homogeneous mixtures, the phenomenon of solvation occurs , which consists of the dissolution of the solute in the solvent. The solute molecules are surrounded by the solvent molecules, giving up their ions to the latter.

The principle that like dissolves like is presented , which means that polar solute molecules only interact with polar solvent molecules. Likewise, nonpolar solutes only interact with nonpolar solvents.

Another property is the solubility of a solution, which is the maximum point at which a solvent and a solute can no longer dissolve. In this case the solution can be:

• Saturated: the solvent is unable to further dissolve the solute.
• Supersaturated: more solute is added to the solution and it remains in its original state.
• Unsaturated: when the amount of solute is less than what the solvent is able to dissolve.

Factors that affect solubility include the polarity and volume (size) of a substance’s molecules, pressure, and temperature.

Learn about the Difference between solute and solvent .

Separation of homogeneous mixtures

Distillation is a method of separating homogeneous mixtures composed of miscible (soluble) liquids or a liquid and a solid. In this case, the liquids are separated by boiling. Once the boiling point of one of the components is reached, it evaporates, separating from the other. An example of this occurs when distilling alcoholic beverages.

Another way of separating homogeneous mixtures is crystallization . In this, the solute in the non-solid phase is made to lose solubility by transforming into a solid. This can be achieved by evaporating the liquid, cooling it, causing a reaction in it or adding some other element. An example of this is found in the production of salt from sea water.

Other separation methods are chromatography, evaporation and solvent extraction.

Examples of homogeneous mixtures

• The air.
• Water mixed with sugar or table salt.
• Vinegar (water + acetic acid).
• Steel (carbon + chromium + iron).
• Bronze (copper + tin).

You may also be interested in seeing 60 examples of homogeneous and heterogeneous mixtures .

What are heterogeneous mixtures?

A heterogeneous mixture is a mixture that is found in at least two different states of matter (two phases), its components are mixed in a non-uniform manner and it is possible to differentiate them with the naked eye.

While in a homogeneous mixture the components are distributed in the same way in any region of the mixture, in a heterogeneous mixture the components are distributed in different quantities. That is, a portion or sample taken from a heterogeneous mixture may contain more or less of some of its elements.

The properties of each component of a heterogeneous mixture are not changed by mixing them. When components are mixed, particularly in a liquid state, they are immiscible . Miscibility means that one element is soluble in another (e.g., table salt in water in a homogeneous mixture).

So, in the case of heterogeneous mixtures, when two liquids are mixed, they maintain their properties, without there being solubility. That is, their elements are immiscible. For example, the mixture between oil and water is a heterogeneous mixture of immiscible liquids.

Characteristics of a heterogeneous mixture

• There is no uniform distribution of the elements that compose it.
• It is common that its components can be distinguished with the naked eye.
• Any mixture that presents two states of matter is heterogeneous.
• Its components are not miscible and remain physically separated.

Phases or states of matter in a heterogeneous mixture

A heterogeneous mixture consists of at least two distinct phases of matter. This means that each element maintains its properties intact.

That is, a heterogeneous mixture can be made up of two liquids that can be separated and differentiated with the naked eye, because each one maintains its particular phase and properties. The same occurs if two or more solids are mixed, as in the case of a mixture of powdered peppers.

Types of heterogeneous mixtures

When the components of a heterogeneous mixture are in different phases (for example, a liquid and a solid), this mixture is known as a suspension .

Suspensions are characterized by the fact that the solid does not dissolve in the other component, be it a gas or a liquid. Even if the components are mixed, they will eventually be found in separate portions of the mixture.

The particles that make up the solid in a suspension are of such size that the Earth’s gravity has an effect on them, overcoming the force that would bind them to the other substance. In addition, it is possible to separate the mixture by means of filtration.

Sand mixed with water is an example of a suspension. If placed in a container and shaken, the sand will eventually settle to the bottom of the container.

Another type of heterogeneous mixture is known as colloids . In these, the particles are smaller than in suspensions, they can only be observed through a microscope and it is not possible to separate them by filtration.

These are characterized by their particles being able to disperse light when it passes through a colloidal mixture, becoming visible, creating the Tyndall effect (named after the Irish physicist John Tyndall, 1820-1893). This phenomenon is due to the particle size of the colloid mixtures.

Mayonnaise is an example of a colloid, specifically an emulsion , since its main components are in a liquid state and one of its elements works as an emulsifier. The ingredients that are normally used to make mayonnaise are oil, water, egg, etc. Water and oil are not soluble in each other, which means that they are immiscible.

Separation of heterogeneous mixtures

Heterogeneous mixtures can be separated using different methods such as filtration, decantation, sedimentation, centrifugation, drying or magnetic separation.

In the case of filtration , this involves separating the components of a mixture that are in different phases or states of matter, specifically a non-soluble solid and a liquid. An example would be using a filter to separate the pulp or other parts of a fruit from the resulting juice.

When a mixture is composed of two liquids that do not dissolve in each other and have different densities, this mixture can be separated by means of the decantation method .

This involves letting the mixture sit in a container and, when one of the liquids remains on the surface, using a funnel to pour it into another container. For example, if you want to separate water and oil, you wait for the oil to reach the surface and then place it in another container.

Other ways of separating heterogeneous mixtures include sedimentation (waiting for one of the components to settle) and centrifugation (separating the components by rotation).

Examples of heterogeneous mixtures

• Ice cubes (solid) in a drink (liquid).
• Cereal (solid) mixed with milk (liquid).
• Sea sand (made up of solids, such as stones, shells, salts, etc.).
• Pizza (made up of different elements in different states).
• Mayonnaise (result of a mixture of different immiscible substances).
• Vinaigrette, which includes water and oil (main ingredients are two liquids).

• Conclusion

  In conclusion, understanding the distinctions between heterogeneous and homogeneous mixtures is fundamental in both chemistry and various real-world applications. Heterogeneous mixtures display visibly different components, while homogeneous mixtures appear uniform throughout. Recognizing these differences not only aids in scientific learning but also enhances our ability to analyze and interact with the world around us. By applying this knowledge, we can make informed decisions in fields ranging from cooking to environmental science, emphasizing the importance of mixtures in our daily lives.

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