1. BATTERIES

2. A battery is a galvanic cell, or a set of cells connected in series, that provides a direct current of consistent strength for a useful period of tie. Two redox half reactions occur at two electrodes. The nature of the reactions depends on the chemicals that make up the cell.

3. A – top, non-conducing seal B - the cathode - a graphite (carbon) rod C - the anode – a cylindrical zinc casing D - the battery is filled with a mixture of manganese dioxide (MnO 2 ) as oxidant, ammonium chloride (NH 4 Cl) as a source of H + ions, and zinc chloride (ZnCl 2 ) (D). These two salts serve as electrolytes. Carbon-zinc dry cell

4. The lead – acid battery. This type of battery is used in car engines. It delivers a large amount of current for a short space of time. A large current is needed to provide the spark across the spark plug, which starts the car. This type of cell is called a secondary cell because it stores energy when the chemical reaction proceeds in one direction and releases energy when it proceeds in the opposite direction.

5. It is rechargeable. A number of cells are connected in series to form the lead-acid battery.

6. Oxidation half reaction – occurs at the anode. Reduction half reaction – occurs at the cathode.