Very few of the chemicals and substances we encounter on a daily basis are in their pure form. Many of them are mixtures. In this lesson, you will learn about the types of mixtures recognized by scientists.
Definition of Mixture
Any substance that has a uniform and unchanging composition is considered to be pure. Examples of pure substances include elements. A mixture is a combination of two or more pure substances in which each pure substance retains its individual chemical properties.
Mixtures can be composed of solids, liquids, or gases.
Examples of Mixtures
Mixtures can be defined in different ways and are classified as either heterogeneous or homogeneous. A heterogeneous mixture is a mixture that does not blend smoothly throughout and in which the individual substances remain distinct. If you have ever seen fresh-squeezed orange juice with the pulp floating in it, then you’ve seen a heterogeneous mixture. Since the pulp continues to float instead of mixing smoothly with the juice component, it makes it a heterogeneous mixture.
Heterogeneous mixtures are classified as either suspensions or colloids. A suspension is a mixture that contains particles that settle out if left undisturbed. A classic example of a suspension is Italian salad dressing. If you’ve ever noticed it sitting on a shelf in the grocery store you will see the solid particles at the bottom of the bottle and the oil at the top. This is why you shake it before you use it. Since the particles settle down to the bottom, it makes Italian dressing a heterogeneous suspension.
A colloid is a heterogeneous mixture of intermediate-sized particles that do not settle out. A classic example of a colloid is milk. While milk looks like one pure liquid, it is actually butterfat suspended in water. The particles are relatively the same size and therefore do not settle out when left undisturbed. This makes milk a heterogeneous colloid.
A homogeneous mixture is a mixture that has a constant composition throughout. Homogeneous mixtures are also referred to as solutions. A classic example of a homogeneous mixture is the metal steel. It is a combination of iron and carbon. Steel has a uniform composition made of carbon and iron. This means that no matter whether you have one gram or one kilogram of steel, you will have a piece with constant composition.
This makes steel a homogeneous mixture.
A mixture is a composition of two or more pure substances. Mixtures are considered to be homogeneous or heterogeneous.
A homogeneous mixture has a constant composition throughout and is commonly referred to as a solution. A heterogeneous mixture does not have a uniform composition and the individual substances retain their properties. Heterogeneous mixtures are referred to as suspensions or colloids depending on the size of the particles and whether or not they settle out when left undisturbed.
Types of Mixtures
|*Also referred to as a solution *Has a constant composition throughout||*A mixture where the individual elements remain distinct within the mixture *Are either colloids (intermediate-sized particles that don’t settle out) or suspensions (particles settle out if undisturbed)|
When you are done, you should be able to name and discuss the different types of mixtures.