Friday, July 4, 2008

Days three and four

Elements, compounds and mixtures! That is the focus of days three and four. All matter can be put into one of those groups. Elements are the purest form of matter. Compounds are a combination of elements that have been chemically bonded to each other. Mixtures are a blend of two or more substances that have been physcially combined. We consider elements and compounds to be "pure substances" because they are made up of only one type of substance. Mixtures can be either homogeneous (all the same) or heterogeneous (see different parts). Solutions are homogeneous... things like granite, chinese food, and soda are heterogeneous. On day three we worked on separating mixtures. First we separated a mixture of four different types of plastics and iron filings. We used any tools that we wanted and figured out the best methods of separation all by ourselves! Great teamwork! Next, we took a sample of "FOUL water" and used some standard separation techniques to clean it up... we allowed the oil to float to the top, then we filtered through gravel and sand, then we added charcoal that absorbed odors and filtered it through filter paper. Even though it looks REALLY clean now... we still have to test it to see if it conducts electricity... when it does we know that it still contains something dissolved in it like salt. To get rid of that we have to distill it.... now it is clean... but NO you can not drink it! YOU DON'T DRINK ANYTHING THAT HAS BEEN IN CHEMISTRY GLASSWARE!

One day four we tried out some more separation techniques... first we separated the different colors in markers using chromotography. We made cooooool round chromotographs. Chromotography separates the dyes by washing the different molecules along the paper. The different molecules (colors) have different attractions to the paper, so they stop in different locations. Next we separated a mixture of shaving cream and food colors using the food colors attraction to paper. This is a cool technique and we used it to make special "postcards" which many of us mailed home!

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