Mixtures

General Chemistry Index

Where are we going with this? The point of this deck is to give the background information and examples so that we can differentiate between substances (pure and mixtures) based on physical and chemical properties.

What are mixtures (impure substances)?

Feels like a definition is coming… Just saying…

Mixtures are composed of two or more types of atoms or molecules that are not chemically combined.

Seriously? Good thing atoms and molecules got introduced elsewhere.

So, basically, if you have a bunch of stuff in the same place and it is not a pure substance, it is a mixture. The difference is that, whereas elements and compounds are made up of a single type of atom or molecule, mixtures are made up of a combination of them.

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Metaphor and example time…

Think of a mixture as a salad. The elements and compounds are the vegetables and whatever else is in the salad. For the purposes of the metaphor, suppose you think of each vegetable as a single, whole thing. If you don't like tomatoes, you can pick them out. Picking them out doesn't change the tomatoes into something else and the lettuce left behind doesn't change into something else. The salad (mixture) changes, but the parts don't.

So, a mixture can be, metaphorically, a salad made up of elements and compounds.

Examples of mixtures are many! Let's go with Kool-Aid. Or powdered sports drinks…

You start with a large quantity of water. You add in a small quantity of powder. Then what? You MIX.

The result is that the powder molecules are spread out throughout and within the water molecules. There are still two different kinds of molecules… the water and the mix. Which is probably also be a mixture of sugar and other things… Since the two or more different types of molecule can be separated back into their original form, they are not pure. They are, therefore, mixtures.

 

https://youtu.be/5D1gAjNwQKw

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Since mixtures are made up of two or more types of atoms and/or molecules, they are not considered pure. But, not all mixtures form the same ways. There are two broad categories of mixtures, and within those, there are some subcategories.

The details of how mixtures behave are different depending on the type of mixture you are considering.

Next slide, please!

Types of Mixtures

Heterogeneous

Homogeneous

https://youtu.be/zeOa7hdMC-o

Mixtures in Fluids

Mixtures in fluids occur in numerous ways.

Separating Mixtures

Depending on their type, mixtures can be separated back into their components. 

Sifting

 

Filtering

 

Centrifugal Separation

 

Evaporation

 

Distillation