Chemistry C3 Part 6

Based on the Edexcel Textbook

pg 126-128 Cells and Batteries

Cells transform energy from chemical reactions into electrical energy. The chemicals inside a cell will react to push electrons around a circuit like a pump producing an electrical force of about 1.5 volts. A group of cells is called a battery.

The first battery was invented in 1799 by a man named Alessandro Volta. It was a pile of zinc and copper plates seperated by cloths that were soaked in salt water. A simple 'wet' cell can be made by putting zinc and copper plates into a beaker of conducting fluid such as dilute sulfuric acid but this is not very easy to use so the 'dry' cell was invented that uses moist paste instead of conducting fluid. Look at the book to see a diagram of how a dry cell works.

Once all the chemicals have reacted the cell is dead and has to be thrown away. Single use cells are called primary cells but you can get secondary rechargable cells in which the chemical reaction can be reversed when attached to the mains supply. These are cheaper in the long run and stop batteries getting sent to landfill sites where dangerous chemicals such as mercury and cadmium can leak.

pg 128-129 Electrolysis

Electrical energy can be used to break bonds between chemicals and split them up into elements in a process called Electrolysis. A substance that is split up is called an electrolyte. The chemical reactions occur at the two electrode rods that are placed into the elctrolyte. Metal electrodes will conduct the electricity but may also take part in the reactions. Carbon electrodes will stay inert.The electrolyte needs to be liquid for the process to work (this can be in solution or melted).

During the electrolysis of salt water hydrogen gas is formed at the negative electrode and chlorine…