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Hydrogen is the most basic of the chemical elements, which are the building blocks of all matter. Other atoms are made up of protons, neutrons, and electrons. But hydrogen only has a single electron and a single proton. It's also the most abundant element, making up about three quarters of all matter in the universe.
Did you know? The United States produces around 85 million cubic metres of hydrogen every year. That’s equivalent to almost 30 times the volume of the Dallas Cowboys’ home stadium.Hydrogen is a colourless, odourless non-metal. In its most common form, it’s extremely combustible. This tendency to burst into flame is what makes hydrogen both a very dangerous and a very useful resource.
Hydrogen was first discovered in 1671 by British scientist Robert Boyle, who had been experimenting with different metals by dipping them in acid. When a pure metal is placed in acid, a type of reaction called a single-displacement reaction takes place. For example, adding a piece of potassium (K) to a solution of hydrochloric acid (HCl) causes the following reaction to occur:
2K + 2HCl → 2KCl + H2
The solid potassium metal reacts with the acid to form potassium chloride, a salt. Meanwhile, the leftover hydrogen atoms combine to form hydrogen gas.
Another Brit, Henry Cavendish, confirmed that hydrogen is a distinct element in a paper published in 1766.
Boyle and Cavendish both noticed that hydrogen gas is very flammable. Specifically, it quickly and violently reacts with oxygen:
2H2 + O2 → 2H2O + Heat
The reaction takes molecules of hydrogen and oxygen and combines them together to form H2O (water). This reaction also releases a lot of heat energy: in other words, fire. Other scientists would later discover that hydrogen provides the fuel that lets stars “burn”.
Did you know? Hydrogen melts at 14 degrees Celsius above absolute zero, which is -273.15 degrees Celsius.
Along with its flammability, Boyle and Cavendish also observed that hydrogen is lighter than air. Just like helium, the second most basic element, hydrogen is great at lifting things like balloons. In fact, it is even better at this than helium. So it was only a matter of time before people started designing hydrogen-filled balloons for transportation. By the early 1900s, large airships that used hydrogen as their lifting gas had become a popular form of air travel.
However, the hydrogen-filled airship craze didn’t last long. In 1937, the airship Hindenburg caught fire and exploded in New Jersey, killing 36 people. Airship designers had known that hydrogen was flammable and that helium was a safer choice, but helium was rare and expensive so they had gone with the more dangerous option anyway. After the Hindenburg disaster, it didn't take long for hydrogen to be abandoned as a lifting gas. At the same time, airplanes were becoming more common.
You’ve probably seen videos of the Space Shuttle launching from the Kennedy Space Center or docking at the International Space Station. Until the program was cancelled in 2011, the Shuttle was the main way for NASA astronauts to get into space. Ever wonder what powered those impossibly huge engines? It was hydrogen.
The Space Shuttle’s main engine was powered by burning liquid hydrogen and liquid oxygen. How much power does burning hydrogen provide? Well, three Space Shuttle engines working together put out roughly the same amount of energy as 13 Hoover Dams. The NASA engineers also understood just how dangerous hydrogen could be. However, they decided to be extra cautious and take advantage of all that raw power anyway.
Lately, people have been increasingly interested in going green. Among other things, that means moving away from burning gasoline to power cars. The nice thing about using hydrogen to fuel cars is that, unlike with gasoline, the waste product isn't a greenhouse gas: it’s water! That is why there has been so much interest in recent years in developing hydrogen fuel cell-powered cars. For example, Toyota plans to start selling a hydrogen-powered sedan in California in 2015.
Did you know? Hydrogen makes up most of the matter in the gas giant planets, such as Jupiter.Unlike the Hindenburg, hydrogen-powered cars store the fuel as a solid rather than as a gas. While the material might burn as a result of an accident, it would be unlikely to explode. The risk is about the same as with a gasoline-powered car. Safety issues aside, a car simply wouldn’t have a gas tank large enough to store enough hydrogen gas to get around town.
Indeed, one of the main problems with using hydrogen as a fuel source for cars is storage. Hydrogen has more energy than gasoline by weight, but it has less energy by volume. That means that you need a pretty big tank of hydrogen gas to drive your car a reasonable distance before refuelling.
Low energy density is why scientists have been looking into converting the hydrogen from a gas to a solid. When hydrogen is absorbed into a solid chemical, it can gain a higher energy density. Academic, industry, and government researchers are all looking into this innovative way of bringing hydrogen to the forefront of the energy economy.
Human understanding of hydrogen has come a long way since its discovery in 1671. It’s been used to lift zeppelins, get into space, and it just might be the power source that fuels the cars of tomorrow.
Are You Ready for Hydrogen-Powered Cars? (Bloomberg Businessweek Videos)
Benefits and Challenges (Energy Efficiency and Renewable Energy, US Department of Energy)
Element Hydrogen (It's Elemental, Thomas Jefferson National Accelerator Facility)
Hydrogen (Periodic Table Of Elements, Los Alamos National Laboratory)
Hydrogen in the Universe (David Palmer, NASA)
Hydrogen Storage R&D Activities (Energy Efficiency and Renewable Energy, US Department of Energy)
Safety issues of hydrogen in vehicles (Frano Barbir, Energy Partners)
Space Shuttle Main Engine (Aerojet Rocketdyne)
Cavendish, H. 1766. Three Papers, Containing Experiments on Factitious Air. Philosophical Transactions of the Royal Society. 56:141-184.