You will need:
- 1/4 cup of table salt
- small beaker
- test tube
- candle/ tea light
- conductivity tester ( torch and cables assembled to do the testing*)
- petri dish *
- glass tube and carbon electrodes*
- 9V battery (DDS)
- battery connector and cables (DDS)
- supply of sodium thiosulfate crystals (DDS)
What we did..
- We set up the small glass tube with bung and two carbon electrodes as seen in the photo.
- We prepared a solution of salt by putting a cm depth of salt in the bottom of a beaker and ten half filling it with water.
- We poured salt solution into the small glass tube so that the two electrodes were just covered.
- We then connected a 9v battery to the electrodes and observed the gasses produced
- We disconnected the battery after about 30 seconds
- We then filled a tiny test tube with salt solution and inverted it before putting i in place over the negative electrode
- When the tiny test tube had filled with gas we took it out and tested it by placing the mouth of the tube in a candle flame
What we found out..
When we passed an electric current through salt solution we found that bubbles of gas were produced at each electrode . The gas that was produced at the negative electrode was collected and ignited using a candle flame. The gas burnt with a squeak pop. The other gas smelt like swimming pools.
The gas that popped if hydrogen gas, the one that smelt like swimming pools is chlorine.
The tekkie bit..
When an electric current passes through a solution containing ions ( like the sodium ions and chloride ions in salt) , the ions can move through the solution. Chemical changes then happen at the two electrodes and sometimes gases are produced. In this example the negative electrode produced hydrogen gas (this came from the water) . The positive electrode produced chlorine gas. In this experiment the electric current was used to split up water and sodium chloride ( salt). Electrolysis is the name of the process when an electric current splits a chemical in this way.