Solutions and Electrolytes

    We began today's class by going over the answers to the Classifying Chemical Reactions post lab.  In case you missed it:


Reaction 1:  2Mg + O2 ---> 2MgO
                  Synthesis
Reaction 2:  2HCl + Mg ---> MgCl2 + H2
                  Single Replacement
Reaction 3:  (NH4)2CO3 ---> CO2 + 2NH3 + H20
                   Decomposition
Reaction 4:  CaCO3 + 2HCl ---> CaCl2 + H2O + CO2
                  Double Replacement
Reaction 5:  CuCl2 + Zn ---> ZnCl2 + Cu
                  Single Replacement
Reaction 6:  3CuCl2 + 2Na3PO4 ---> Cu3(PO4)2 + 6NaCl
                  Double Replacement
Reaction 7:  NaOH + HCl ---> H2O + NaCl
                  Double Replacement


    Next, Mr. Lieberman went over some new notes.  We talked about solutions and electrolytes.  A Solute is what is being dissolved in a substance (in this case we mainly focused on water).  A Solvent is what is doing the dissolving.  For example:  You have water and salt.  Water is the solvent and salt is the solute because it is being dissolved in the water.  A solvent can be anything from a liquid, solid, or gas.  Water dissociates ionic compounds into its ions (meaning that it takes them apart).  Example:  NaCl ---> Na+ + Cl-.  Another example we used is the rock salt you pour on your driveway and sidewalks in the winter.  The formula for it is CaCl2 but when it dissolves in the snow (water) you get Ca (charge of 2+) and 2Cl (charge is -).  


    If the compound happens to be covalent, the formula stays the same but changes whether it is a gas, solid, or liquid.  For example:  CO2 (g) ---> CO2 (aq).  

    Electrolytes are basically ionic compounds that carry a charge.  Strong electrolytes are a solution containing enough ions to carry a current efficiently (complete ionization).  A weak electrolyte is a compound that doesn't completely dissociate (small amount of ionization).  


    Electrolytes are essential to our lives.  Without them we would die.  Athletes drink gatorade because they want those electrolytes.  Mr. Lieberman also brought up your nervous system.  Neurotransmitters work as ions too.  Your nervous system passes electrical currents all the time.  


    Mr. Lieberman conducted an experiment to show the presence of electrolytes.  The goal was to light a lightbulb.  At first this was attempted by placing a beaker of salt under the lightbulb where the metal ends were.  The lightbulb did not light.  Then the same thing was done with sugar.  The bulb still did not light.  Water was used next but the electrolytes were to weak to light the bulb.  When adding a little salt to the water the electrolytes were strengthened and were able to light the bulb.  When even more salt was  added the electrolytes were even stronger and the light was brighter.  

Strong Electrolytes

No Electrolyte

Weak Electrolytes

    That sums up today's class.  We received a worksheet titled Dissolving that you should begin to complete.  The unit test has been postponed to next friday.  Hope everyone has a happy Thursday and a good night!!  

The next scribe will be..................... Nicole C.

Good Luck! :)