Current Events
MEMBERS
2 Members

Teaching Jobs on Teachers.Net

Start a new discussion...
I have seen this little experiment done in classrooms. But it is based on bad science, and it could be dangerous.

The basic experiment involves dropping a 9-volt battery into a glass of salt water, and watching the "hydrogen and oxygen" bubble off as the electricity electrolyzes the water.

The truth is that those gases are hydrogen and chlorine. The salt changes the chemical reaction. The experiment teaches this reaction:

2 H2O + energy -> 2 H2 + O2

But adding salt changes the reaction to:

2 H2O + 2 NaCl + energy -> H2 + cl2 + 2 NaOH

Both the chlorine gas and the sodium hydroxide (lye) left in the glass are poisons. If the reaction is allowed to continue long enough, the concentrations could approach harmful values.

An electrolyte that enters the reaction produces different compounds:

salt: hydrogen, chlorine, and lye baking soda: hydrogen, carbon dioxide, and lye k-salt (KCl): hydrogen, chlorine, and potash ...See More


Teacher Chatboards

States

Subject Areas

Language Arts

Foreign Language