How to make a chemical current source

How to power Christmas light using chemistry

How can you make a chem­i­cal cur­rent source? Find out with our ex­per­i­ment.

Safe­ty pre­cau­tions

Warn­ing! Con­duct the ex­per­i­ment only un­der adult su­per­vi­sion.

Reagents and equip­ment

  • cop­per(II) sul­fate so­lu­tion;
  • zinc sul­fate so­lu­tion;
  • cop­per and zinc elec­trodes;
  • croc­o­dile clips;
  • plas­tic vials;
  • vial hold­er;
  • Christ­mas lights;
  • LED;
  • sy­ringes;
  • rec­tan­gu­lar pieces of fab­ric.

Step-by-step in­struc­tions

In­sert cop­per and zinc elec­trodes into plas­tic vials and ar­range them so that the met­als al­ter­nate. Con­nect the elec­trodes with croc­o­dile clips so that the elec­trodes on ei­ther side have a free clip. Con­nect the vials with cop­per and zinc elec­trodes with pieces of fab­ric. Pour cop­per(II) sul­fate so­lu­tion into the vials with the cop­per elec­trodes, and zinc sul­fate so­lu­tion into the vials with the zinc elec­trodes. We’ve cre­at­ed two con­nect­ed Daniell cells. Con­nect the free ends of the clips to an LED — it glows! If you con­nect more Daniell cells, you can even pow­er Christ­mas lights!

Pro­cess­ de­scrip­tion

The prin­ci­ple be­hind the Daniell cell is based on the dif­fer­ence be­tween the re­ac­tiv­i­ty of cop­per and zinc. Its volt­age is ap­prox­i­mate­ly 1.1 volts. Zinc is a more ac­tive met­al. And each zinc atom eas­i­ly gives up two elec­trons, form­ing zinc ions Zn²⁺, which are re­leased into the so­lu­tion:

Zn - 2e → Zn²⁺

These elec­trons mi­grate to the cop­per elec­trode, which de­vel­ops a neg­a­tive charge and be­gins at­tract­ing the pos­i­tive­ly-charged cop­per ions Cu²⁺ in the cop­per(II) sul­fate so­lu­tion. These ions ac­cept the avail­able elec­trons to form metal­lic cop­per, which pre­cip­i­tates on the sur­face of the cop­per elec­trode:

Cu²⁺ + 2e → Cu⁰

As they move through the wires from zinc to cop­per, the elec­trons cre­ate an elec­tric cur­rent, which makes the LED glow.

A sim­i­lar ex­per­i­ment is in­clud­ed in the “Chem­istry & elec­tric­i­ty” set from the MEL Chem­istry sub­scrip­tion.