Electrochemical Cells (Batteries) 10.5

Electrochemical Cells Section 10.5 (Batteries) Cell is another name for battery. Cells are classified as either primary or secondary (rechargeable). 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.*

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.

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.

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.

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.

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.