In chemistry, a mixture is matter consisting of two or more chemical constituents that are not chemically bonded to one another. So, combining components does not cause a chemical reaction that forms new products. In contrast, a pure substance consists of only one kind of matter that has a constant chemical composition, either in the form of an element or a compound. Here is a look at the types of mixtures, their properties, and mixture examples.
- A mixture consists of two or more chemically distinct components that do not react with each other.
- Mixtures can be solids, liquids, gases, or a combination of states of matter.
- A homogeneous mixture has a uniform composition, while a heterogeneous mixture has a non-uniform composition.
- Examples of mixtures include air, salt water, brass, rocks, and soft drinks.
Examples of Mixtures
Mixtures may be solids, liquids, gases, or a combination of states of matter. Here are examples of mixtures:
- Air
- Salt water
- Sterling silver
- 14k gold
- Steel
- Pile of rocks
- Tossed salad
- Water and sand
- Fruit in gelatin
- Sugar and salt
- Soft drink
- Sugar and sand
- Natural gas
- Blood
- Gunpowder
- Ink
- Bowl of candies
- Crude oil
- Soup
Properties of a Mixture
A mixture has properties that distinguish it from a pure substance:
- Separating the components of the mixture is possible. For example, you separate a mixture of salt and sand by shaking them through a mesh or dissolving the salt. You separate salt and sugar by dissolving the sugar in alcohol. Separating a mixture of colored candies is as simple as picking out the different colors.
- The components of a mixture maintain their properties. So, if you mix sugar and sand, the components of the mixture are chemically identical before and after mixing. In contrast, if you combine baking soda and vinegar, a chemical reaction occurs and you get sodium acetate, water, and carbon dioxide.
- The possible proportions of components varies. In a chemical reaction, precise ratios of reactants yield products. But, you can combine the constituents of a mixture in any proportions. For example, you can have a mixture of 90% sand and 10% water or 50% sand and 50% water.
Types of Mixtures
The two broad categories of mixtures are homogeneous and heterogeneous:
Homogeneous Mixture
The constituents are evenly distributed or uniform in a homogeneous mixture. When you take a sample from one part of the mixture, it has the same composition as a sample taken from another region. Solutions and alloys are two important types of homogeneous mixture.
- Solution: A solution is the homogeneous mixture that forms when one constituent dissolves into another. For example, dissolving salt in water makes saline solution. Dissolving sugar in water makes a solution of sugar water. Water and alcohol dissolve in each other, forming a solution.
- Alloy: An alloy is a homogeneous mixture that contains at least one metal and has overall properties of a metal. An example is steel, which is an alloy containing iron, carbon, and other elements. Other alloys include sterling silver, 14k gold, brass, and bronze.
Heterogeneous Mixture
In contrast to a homogeneous mixture, a heterogeneous mixture lacks a uniform composition. So, if you take a sample from one part of a heterogeneous mixture, you get different amounts of the components. For example, when you take a second bowl of chunky soup, you get more of some ingredients than the first bowl and less of others. Types of heterogeneous mixtures include suspensions and colloids.
- Suspension: A suspension is a heterogeneous mixture of fine solid or liquid particles in a fluid. Over time, the components of a suspension typically settle out. An aerosol is a suspension of tiny particles in a gas. Examples of suspensions include flour mixed with water, dust and soot in air, muddy water, and chalk dust suspended in water.
- Colloid: A colloid contains tiny particles of one component that are distributed in another medium. Milk, smoke, and gelatin are examples of colloids. Note that a colloid is visually homogeneous, but it is heterogeneous under magnification.
References
- Alberts B.; et al. (2002). Molecular Biology of the Cell (4th ed.). Garland Science. ISBN 978-0-8153-4072-0.
- IUPAC (1997). “Mixture.” Compendium of Chemical Terminology (2nd ed.). (the “Gold Book”). Oxford: Blackwell Scientific Publications. ISBN:0-9678550-9-8. doi:10.1351/goldbook
- Petrucci, Ralph H.; Harwood, William S.; Herring, F. Geography (2002). General Chemistry: Principles and Modern Applications (8th ed.). Upper Saddle River, N.J: Prentice Hall. ISBN 978-0-13-014329-7.
- Weast R. C., Ed. (1990). CRC Handbook of Chemistry and Physics. Boca Raton: Chemical Rubber Publishing Company. ISBN 978-0-8493-0470-5.
- Whitten, K.W.; Gailey, K. D.; Davis, R. E. (1992). General Chemistry (4th ed.) Philadelphia: Saunders College Publishing. ISBN 978-0-03-072373-5.