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Energy transfers – fuel cells

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Fuel cells produce electricity through the reaction of a fuel with oxygen. Hydrogen-oxygen fuels cells use hydrogen as their fuel, and are useful in cars and spacecraft. Water is the only waste product from a hydrogen-oxygen fuel cell, so they cause less pollution when in use.

Hydrogen-oxygen fuel cell

The reaction between hydrogen and oxygen is exothermic- it releases energy to the surroundings:

hydrogen + oxygen → water

2H2 + O2 → 2H2O

Fuel cells use the reaction between a fuel and oxygen to produce electrical energy. They are efficient and convert a large proportion of the chemical energy in the fuel into electrical energy. Hydrogen-oxygen fuel cells use hydrogen as their fuel.

Energy level diagrams – Higher tier

An energy level diagram shows the changes in energy during a reaction.

The reaction between hydrogen and oxygen is exothermic, so the energy level of the reactants [reactant: One of the starting substances in a chemical reaction. is higher than the energy level of the products [product: A substance formed in a chemical reaction. - and the arrow between them points downwards.

Diagram showing the change in energy during a reaction between hydrogen and oxygen. The reaction is exothermic, so the energy level of the reactants is higher than the energy level of the products and the arrow between them points downwards

Energy level diagram for the reaction in a hydrogen-oxygen fuel cell

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