What Is A Mixture In Chemistry?

by Kate Onissiphorou

A mixture is a combination of two or more substances that do not chemically react. As we explain later on, mixtures can either be heterogeneous or homogeneous.

Mixtures are defined based on how the constituents are combined. They could be a combination of various states of matter, for example, air dissolved in water, or a combination of solids such as the mixture of cement, sand, and aggregate. 

The proportion of the constituents often determines the type and physical properties of a mixture. In other cases, however, the proportion is not very important, and it may only be incidental.

Mixtures occur naturally, such as in the case of air, which is a mixture of 78% nitrogen, 21% oxygen, and 1% other gases. Mixtures can also be artificially created at very precise proportions for specific purposes. For example, steel is a mixture of carbon, iron, and other metals.

Definition of a mixture in chemistry

In chemistry, a mixture is defined as a physical combination of two or more substances that do not produce a chemical reaction. 

This means that chemical bonds are neither created nor broken between atoms. The individual constituents therefore retain their unique chemical properties. Scientist mixing chemicals in a lab

Nonetheless, the molecules of the constituent substances of a mixture may form static electrical attractions. Ions may also be formed in the process, such as in the case of salt being dissolved in water. In this type of mixture the constituents are a bit harder to separate.

Different types of mixtures

Generally, mixtures can be categorised into two main groups – heterogeneous and homogeneous.

An infographic showing the differences between heterogeneous and homogeneous mixtures 

Heterogeneous mixtures have distinct or easily identifiable constituents. Mixtures of this type are also easy to separate. Some may not even require any active effort or energy to be separated. 

Homogeneous mixtures have constituents that are virtually indistinguishable from each other. They tend to be harder to separate and require more effort and energy.

These are some examples of different types of mixtures:

  • Solutions – these are homogeneous mixtures that contain two main components – the solvent and the solute(s). The solvent dissolves the solute. Generally speaking, the solvent is proportionally greater than the solute(s). ReAgent employee mixing a solution
  • Alloys – an example of a homogeneous mixture, alloys are characterised by two or more solid elements (at least one of which is a metal) that are mixed together. This is done to either strengthen the alloy or produce other desirable characteristics, for example, tarnish resistance. Much like a solution, one component (the metal) is proportionally greater than the other constituents.
  • Suspensions – in this type of heterogeneous mixture, solid particles are mixed with a liquid but the particles do not dissolve. Suspensions easily separate once the mixture is allowed to settle.
  • Colloids – these are heterogeneous mixtures with small particles that are evenly distributed in the liquid medium. Colloids are similar to a solution, but the particles aren’t dissolved.

Examples of mixtures in chemistry

Mixtures are either intentionally mixed or they are naturally-occurring. As we mentioned before, they can also be homogeneous or heterogeneous. Here are some examples of mixtures in chemistry:

  • Sand and water – on a beach, the water and sand exist as a heterogeneous mixture. The water can be easily separated from the sand.
  • Salt and water – the marine ecosystem is distinguished by its high salt content. The entire ocean is a homogeneous mixture of water, salt, other minerals, and organic substances.
  • Sugar and salt – if you combine sugar and salt and mix them well, it becomes a heterogeneous mixture. Although the two crystalline substances are the same colour, they are still distinguishable from each other.
  • Ethanol in water – wine, gin, whisky, and other alcoholic beverages are basically a homogenous mixture of ethanol and water. Ethanol is the only alcohol that can be consumed by humans without killing them.

    Man measuring wine in a test tube
    Wine is a homogeneous mixture of ethanol and water

The difference between mixtures and solutions

Solutions are a homogeneous type of mixture. Mixtures, however, is a more general term that encompasses other types such as colloids and suspensions. 

The distinguishing characteristic of solutions as mixtures is the fact the solutes are dissolved in the solvent. This means the solutes have become incorporated with the solvent and evenly distributed, either as molecules or ions.

In conclusion

In chemistry, mixtures are classified into general and specific categories. Each one has characteristics that are unique to that particular category. Mixtures exist naturally but some are made intentionally for a specific purpose. Although the substances in a mixture physically merge, their unique chemical properties do not change.

Disclaimer

The blog on chemicals.co.uk and everything published on it is provided as an information resource only. The blog, its authors and affiliates accept no responsibility for any accident, injury or damage caused in part or directly from following the information provided on this website. We do not recommend using any chemical without first consulting the Material Safety Data Sheet which can be obtained from the manufacturer and following the safety advice and precautions on the product label. If you are in any doubt about health and safety issues please consult the Health & Safety Executive (HSE).