One rumour floating around is every environmentalist’s dream – cars which run on nothing but water.

PAZDA is here to say “No!”.

All chemical processes can either be classified as exothermic or endothermic. If the process is exothermic, energy in the form of heat is released and this energy can be used to power our machines. This imposes a limitation on the car industry, as only fuels that undergo (resultant) exothermic chemical processes can be used to power our cars.

Have a look at the energy level diagram of the possible combinations of hydrogen and oxygen molecules.

The above enthalpy diagram of a hydrogen-oxygen system illustrates the enthalpy changes of the various possible compounds involving the two elements. The red arrows show endothermic reactions.

We want to run a car on liquid water. However, liquid water exists at the lowest energy level in the system! We can’t convert water to anything else in this system because liquid water is unable to undergo any known exothermic reactions in a hydrogen-oxygen system. Therefore, as water is unable to undergo any chemical process that produces heat, it is unable to take on the role of fuel for cars.