Example 1 - Electrolysis of water and sodium chloride (salt)
Put two electrodes into a salt water solution.
Connect a direct current (standard battery) to the two electrodes. In this case, the electrodes are graphite, an unreactive material, and the liquid is salt water (NaCl + H2O).
When the circuit is switched on it is found that bubbles are formed on each electrode. So gases are being produced.
The gases are collected and tested to see what they are. (Both are colourless)
The test tube from the +ve (positive) electrode (anode)
The damp, blue litmus paper goes red then is bleached white, which is a sure sign that the gas is chlorine.
The test tube from the -ve (negative) electrode (cathode)
The lighted splint causes a “POP”, which is the test that concludes that the gas is hydrogen.