Introduction to Solutions

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A solution is a particular type of mixture. Mixtures in chemistry are combinations of different substances where each substance retains its chemical properties. Generally, mixtures can be separated by non-chemical means such as filtration, heating, or centrifugation.

A solution is a homogeneous mixture, but that's not the full definition. Homogeneous means that the mixture is the same all the way through. You could take two same-sized samples: one from the bottom and one from the top and they would be identical. Homogeneous mixtures do not settle out if left to sit undisturbed, whereas a heterogeneous mixture would. Blood is a good example of a heterogeneous mixture.

A solution is a homogeneous mixture where all particles exist as individual molecules or ions. This is the definition of a solution.

By the way, there are homogeneous mixtures where the particle size is much larger than individual molecules. However, the particle size is so small that the mixture never settles out. Terms such as colloid, sol, and gel are used to identify these mixtures. Even though their study is an important part of chemistry, the ChemTeam will only focus on solutions.

A solution has two components: the solute and the solvent.

The solvent is the substance in greater amount.

It is usually a liquid, although it does not have to be. It is usually water, but it does not have to be. The ChemTeam will focus on water only and will leave non-aqueous solvents alone.

The solute is the substance in lesser amount.

It is usually a solid, although it does not have to be. The ChemTeam will focus mostly on solid solutes, but the occasional liquid solute will get mentioned.

Ya know, I can just see that gleam in your eye. "OK, Mr. hot-shot ChemTeam," you say, "what about a situation where both substances are in equal amount?" That's easy - the water is the solvent. "But," you say, "it's not water, it's, it's ALCOHOL." No problem - the liquid substance is the solvent. "But...," you start to say as I ....

You finish the story.

The word concentration refers to how much solute is dissolved.

Dilute means that only a little solute is dissolved and concentrated means a lot is dissolved.

Dilute and concentrated are NOT used when it comes to numbers and solutions, but they are words you should be familiar with.

There are two major concentration words that are numerical in nature: molarity and molality. Usually molarity is introduced first in beginning classes, so go there first.

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