Lesson 4



LESSON 4.  Breaking Bonds - Lab



2 carbon rods (5-7 cm long)
2 alligator clips
6 volt battery
250 ml beakers,
2 test tubes or 10 ml graduated cylinder
wood stick (long)

Objective:  Students will learn about methods to break bonds by experimenting with electrolysis.


Teacher Notes:

Electrolysis of pure water proceeds slowly because the concentrations of H+ and OH-  ions are too small to carry an appreciable current. The electrical conductivity can be increased by adding H2SO4  (an acid) or NaOH (a base), which produce H+ and HSO4- ions or Na+ and OH- ions. Since the ions carry the electrical current, their presence permits more current to flow through the solution.  Hence more electrons enter and leave the electrolytic cell.

Do not use NaCl (salt) in your liquid to speed up the experiment.  It will create small amounts of chlorine gas.  We suggest using Epsom salt (magnesium sulfate, MgSO4).  Also note that we recommend 6 volts, although other voltage can work, the higher the voltage the quicker the reaction).


You may want to substitute test tubes with graduated cylinders, if you want the students to record the amount of gas collected.   



1.  Bubbles can be seen coming from both the anode and cathode

2.  One has double the amount of gas as the other
3.  You can hear small “pops”, hydrogen
4.  Oxygen, a flame returns indicates oxygen
     Conclusion:  yes you can break up water into its components of hydrogen and oxygen


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