Rarely they can't with just sight. Certain tests or experiments should take place
i just learnt this recently but i need to look through my notes again.
Answer:
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Explanation:
Electrolysis of acidified water
Water is a poor conductor of electricity, but it does contain some hydrogen ions , H +, and hydroxide ions, OH -. These ions are formed when a small proportion of water molecules naturally dissociate . ... H + ions are attracted to the cathode , gain electrons and form hydrogen gas.