Mixtures vs. Pure Substances What is a mixture or a pure substance ? What is the difference between the two?

Mixing & Separating Here we have two very common substances, Water and Salt Separated, they are both pure substances But when we mix them together we form a solution… The salt dissolves into the water How can we separate them back into two separate substances again?

Dissolving the Salt We will super saturate 200 ml of water with 5 table spoons of salt Stir the solution until the salt has completely disappeared What happened to the salt? Can we get it back?

Distilling the Water By boiling the water it turns into vapor However, the salt particles can not stay attracted to the water particles when they turn to vapor Therefore they are left behind… after all the water has been evaporated, only salt is left

Mother Natures Device Where else does this this process take place in nature? Do we benefit from it?

The Water Cycle

The Break Down All matter is either a pure substance or a mixture The purest substances that we can break matter into are ELEMENTS

Elements Once a substance has been broken down into its elements, we can no longer separate it any more… You cannot take gold bars, and separate them down any further into two other substances… gold is the last stop!! The same goes for all of the elements

Pure Substances For our purposes… We will say that pure substances are anything that is made up of a single type of matter Examples of Pure Substances are: - Salt - Water - Oil - Aluminum

Mixtures Mixtures are a combination of two or more pure substances There are 4 categories of Mixtures Examples of Mixtures are: - Koolaid - Oil sands - Blood - Stew

Categories of Mixtures are: Mechanical Mixtures Any mixture where the different components of the mixture can be easily seen with the naked eye Solutions Any mixture where the different components can not be seen separately. Solutions appear to be one pure substance

Categories of Mixtures are: Suspensions This is a mixture where tiny droplets of one substance are held within another substance… eventually one will settle out! Colloid A cloudy mixture, but the droplets of the solute are so small, they can not be separated easily

Categories of Mixtures are: This is a mixture where tiny droplets of one substance are held within another substance and WON’T settle out.

Categories of Mixtures are: What’s the difference between a suspension and a solution? In solution, the particles of the different substances are attracted to each other so they will not separate unless acted upon by an outside force In suspension, DO NOT have that attraction… if we let the mixture sit still for a while, the particles would eventually settle out and separate themselves

Suspensions vs. Solutions Particles in a suspension mixture will settle out over time if they stand still… solutions will not.

The Tyndall Effect Demo Time… Kill the lights!!!

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Mixtures a HOMOGENEOUS solution is one where the different substances making up the mixture can not be seen as separate… this would be a solution Examples are: fruit juice or salt water

Mixtures a HETEROGENEOUS mixture is one where the different substances making it up can be seen Examples are: Soil or stew

Solution Terms Dissolving – The process of mixing a solute into a solvent to form a solution Solute – The substance that is dissolved into the solvent, usually in a lesser quantity Solvent – The substance that has the solute dissolved into it, usually in higher quantity

Break down of Matter All Matter Pure SubstancesMixtures MechanicalSolutions Suspensions + Colloids HomogenousHeterogeneous

Did we get Salt? Looking back at our distillation process… we can see that our water from the original container has now been re purified and is in a separate container We can also see that the salt has been left behind in the form of dry salt crystals

Your Homework You are being a handout that covers the material we just went over… Work on these questions and we will go over them in the next class. For more info on this topic… you can read the following pages from the two textbooks: Pages in the Science in Action 8 Textbook Pages in the Science Focus 8 Textbook