Hydrogen combustion is the process by which hydrogen reacts with an oxidizing agent and burns. Hydrogen combustion is an exothermic combustion, meaning that it releases heat energy. Endothermic processes, on the other hand, absorb energy. Hydrogen burns based on the chemical formula 2H2 + O2 → 2H2O, meaning that it reacts with oxygen. While it is not shown in the chemical equation, an input of energy is necessary to begin the reaction, which releases a significant amount of energy when carried through to completion.
Combustion reactions are more often simply called burning. There are two parts that are essential to combustion reactions, including hydrogen combustion: a fuel and an oxidizing agent. With the input of heat, hydrogen reacts with oxygen to release heat and light energy. The end products of the reaction include water vapor and heat. The input of heat is necessary to overcome the attractive forces between atoms and molecules; the energy released comes from the energy that was stored in chemical bonds that are broken during the reaction.
Hydrogen combustion has shown some potential for powering automobiles and generating energy to meet other human needs. However, because of the energy input needed and the comparatively low energy output, it is difficult to utilize it efficiently. Fossil fuels are more commonly used for fuel and energy, but the supply of such fuels is very limited and their combustion releases harmful gases into the atmosphere. Hydrogen, on the other hand, is a hugely abundant resource that only produces water vapor when burned. As such, energy researches are making significant progress in the development of hydrogen-based fuel cells; some have already been used in automobiles to varying degrees of effectiveness.
While it is still a relatively new area of study, there are several different kinds of vehicles that have been made to utilize hydrogen combustion because of its cleanliness and its renewable nature. Large quantities of hydrogen are actually used to launch space shuttles into space. Smaller vehicles, such as boats and motorcycles, have also been made to utilize hydrogen combustion.
One famous example of hydrogen combustion is the Hindenburg explosion. The Hindenburg was an airship that was held aloft by massive quantities of hydrogen. Something aboard the airship triggered an explosion which ignited the hydrogen, causing the massive airship to explode violently, killing 35 people. Many different theories have been put forward to explain the sudden explosion, but the true cause was never conclusively determined.