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Activity

Electrolysis with home made wires

Summary: 
Make circuits that include a salt solution, to generate gas at the electrodes.
Science content (2016 curriculum): 
Chemistry: Chemical Changes (2, 7)
Physics: Electricity, Electromagnetism (7)
Lessons activity is in: 
Materials: 
Procedure: 

Add a couple of teaspoons of salt to a tub of water and stir to make a solution.
Using the home-made wires from the Electric circuits activity, tape one end of each wire to the batter and dip the other end of each wire into the salted solution.
Make sure the wires are not touching (which would make a short circuit that bypasses the salt solution). Watch for bubbles coming from the wires that are in the water (called electrodes).
The salted water allows electricity to pass, and bubbles of gas are produced at each terminal: hydrogen and chlorine. At one electrode hydrogen gas is produced as the H+ ions in water gain an electron from the electrode, join together to form H2 molecules. At the other electrode, chlorine gas is produced as Cl- ions give an electron to the electrode, join together and form Cl2 molecules. The amounts of chlorine are similar to the amount released by a bottle of bleach: too small to be harmful if not contained, but do not let students enclose the gas or smell large amounts of it.

Notes: 

Can also try baking soda, sugar, or other kitchen chemicals, to see which allow current to pass and which do not. The students were not interested enough in this to try other solutions. (They were occupied with immersing a bulb-and-battery circuit in water.)

Collet the hydrogen gas over water, ad make a pop.

A higher voltate (9-12V) should allow electrolysis of water (into hydrogen and oxygen gases). 2H+(aq) + 2eāˆ’ ā†’ H2(g) and 2H2O(l) ā†’ O2(g) + 4H+(aq) + 4eāˆ’

Electrolysis of salt solution or water produces OH- ions. Can the pH change of the solution be measured?

Grades taught: 
Gr K
Gr 1
Gr 3
Gr 4
Gr 5
Teacher: 
Ingrid
Teaching site: 
General Gordon Elementary Science Club
Activity originally developed and delivered: 

Gordon Elementary Science Club