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Mix it Up! Separate Particles in Different Kinds of Mixture

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Author: Janice VanCleave

What You Need to Know

A mixture is a combination of two or more substances that can be separated by physical means. A solid that will dissolve in a liquid is said to be soluble in that liquid. A solid that will not dissolve in a liquid is insoluble in that liquid. Filtration is the physical process of using a porous substance (a filter) to separate a solid from a liquid. The liquid that passes through the filter is called the filtrate, and the solid collected by the filter is called the residue.

How Does a Mixture Work?

A mixture contains substances that retain their separate identities. The individual substances remain visible in some mixtures, such as a mixture of salt and pepper. In other mixtures, the dissolving substance breaks into particles that are too small to see. For example, a mixture of sugar and water forms a solution in which the sugar particles are present but are not visible.

What Does This Have to Do with Separating Substances in a Mixture?

The process of separating particles in a mixture depends on the characteristics of the particles. For example, an insoluble solid, such as a rock mixed with water, can be separated by filtration. Soluble substances must be separated by other methods. For example, a mixture of sugar and water forms a solution in which the sugar particles can be separated by evaporation of the water.

What Does This Have to Do with Separating Substances in a Mixture?

Real-Life Science Challenge

Pollutants (any unwanted substance) that are spilled into the ocean have to be separated and taken out of the water to protect marine life. The characteristics of the pollutants determine what processes are used for this separation. Oil spills are very damaging to wild-life. For example, oil on the wings of birds makes it difficult or impossible for the birds to fly. Much of the spilled oil can be separated from the water because oil is insoluble in water. It is also less dense than water, which causes it to float on the surface of the water. This makes it possible to remove the oil by sucking it off the surface. Unfortunately, spilled oil that reaches the shore covers rocks and is absorbed by the sand. This oil can kill things living in these areas and is difficult to remove.

Fun fact

Perfume is a solution of a solvent and different solutes. The solutes include the scents called "notes." Just as musical notes must be combined to create music, scent notes are combined to make certain fragrances. The scent notes separate from the mixture as they evaporate at different rates. The notes that evaporate first are called the top notes. These are light fragrances that you smell when you first open a perfume bottle, and they last a few minutes. The middle notes are apparent about 15 minutes after application and last about one hour. The bottom notes are the last to evaporate, and their fragrance lasts the longest, usually several hours.

Experiment

Now, start experimenting with separating the particles in different kinds of mixtures.

Caution:You want to mix substances that do not create chemical reactions. Have an adult supervise and approve the mixtures you make. Avoid household cleansers, which can produce toxic materials when mixed together.

Hints

  • Safe substances to mix include water, tempera paints, food coloring, fruit juices, salt, sugar, pepper, Epsom salts, and dirt.
  • Physical characteristics of substances can sometimes lead to unique separation techniques. For example, magnets can be used to separate magnetic materials from nonmagnetic ones.
  • Filters can be porous papers, such as a coffee filter, or a porous solid, such as charcoal or sand.
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