Tuesday, November 9, 2010

Conductivity Lab

            We recently have been learning about atoms and we are talking about their break down or build up into ions. Certain atoms of substances are much more likely to become ions than others. For example, Sodium has an electron configuration of 1s22s22p63s1. Because of this, Sodium is often found in its ion form Na+, this means that often sodium looses an electron to become stable like neon. This makes it a pseudo-noble gas with the configuration of 1s22s22p6. This was just one example and we figured if sodium was likely to make ions then so were other elements. We constructed & preformed a conductivity lab. In this lab we tested 8 different substances dissolved in distilled water with the purpose of finding out which solution held a greater concentration of ions. For each solution we would record our prediction of how high the ion concentration would be ranging from none to very high. From here we tested with a simple, store-bought, battery-powered, ion concentration detector. This only detected from none-very high, it gave no numbers & no precise measurements. After we tested all of these with this conductivity tester, we tested these substances with the conductivity probe. This probe can accurately measure these solutions to give us even a better idea of how highly concentrated each solution was. 
            Here is the data we collected:
Substance                 Prediction            result w/ tester              result w/ probe (uS/cm2)
Methanol                      high                     very high                            249.2
Calcium Chloride       medium                  very high                            246.6
Albumin                     medium                  very high                            248.7
Cupric Oxide               low                         low                                   22.4
Ammonium Sulfate    very high                  very high                            249.3
Glucose/ Starch            low                         low                                   35.0
Citric Acid                   high                         high                                 249.3
Sugar Water                 low                         low                                   16.1

            From this data we can conclude that certain dissolved substances such as Ammonium Sulfate and Citric Acid have a much higher concentration of ions than substances like Sugar Water and Gluscose. In some cases, substances wouldnt always dissolve well in the water to give a very accurate concentration reading (Ex: Cupric Oxide). Overall, we learned that many dissolved substances have concentrations of ions whether high or low.  

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