Electrochemical Cells (Batteries)

1. Electrochemical Cells (Batteries) 10.5

2. Electrochemical Cells • Cell is another name for battery. • Cells are classified as either primary or secondary. • In a primary cell, chemical reactions use up some of the materials in the cell as electrons flow from it. They can’t be recharged. • When these materials have been used up, the cell is said to be discharged and cannot be recharged.*

3. Primary Cells • Primary cells can be further classified as either wet or dry. • The primary wet cell was first developed in 1800 by Italian scientist, Alessandro Volta. • This cell is therefore called the voltaic cell.

4. Primary Wet Cells • A wet cell is made up of two pieces of metal that are placed in a liquid. • The metal plates, usually zinc and copper, are called electrodes. • The liquid in the cell is called the electrolyte. • An electrolyte is any liquid that conducts an electric current.

5. Primary Wet Cells • Electrons collect at the positive and negative terminals of the cell. • The cell will only discharge when connected to a closed circuit.

6. Primary Dry Cells • The dry cell is similar to the wet cell, but the electrolyte is a moist paste instead of a liquid. • When most of the negative electrode has been used up by the chemical reaction, the electrons stop flowing and the cell is discharged. • A group of cells make up a battery.

7. Secondary Cells • Unlike primary cells, a secondary cell can be discharged and recharged many hundreds of times. • Secondary cells are often referred to rechargeable batteries. • Secondary cells are so named since there are two chemical processes involved: • one to discharge the cell • one to charge the cell • A car battery consists of a group of secondary cells.