Energy Changes: Chemical Cells and Fuel Cells

A cell is composed of two electrodes dipped in an electrolyte solution. It produces electricity from a chemical reaction.

A battery consists of two or more cells connected in series.

• the metals used as electrodes • the concentration of the electrolyte • temperature of electrolyte • type of electrolyte

• convenient • some are rechargeable

• contain harmful chemicals

Rechargeable - chemical reactions are reversed when an external current is supplied Non-rechargeable - reactants (ions in electrolyte and metal ions on the electrodes) are used up, cannot be recharged

Fuel cells are supplied by fuel and oxygen to oxidise the fuel and to generate electricity?

2H2 + O2 → 2H2O

2H2 → 4H+ +4e-

O2 + 4H+ + 4e- → 2H2O

• no pollutants releases like CO2 • no recharging

• H2 is flammable and a gas so difficult to store • fossil fuels may have to be used to produce them

• The electrolyte contains ions which react with the electrodes. • The chemical reaction between the electrolyte and the electrodes sets up a charge difference between the electrodes • The electrodes are connected by a wire allowing the change to flow producing electricity.

the sum of the voltage of all the cells

something that conducts electricity, this is usually metals