Kolkata, West Bengal
Henry Cavendish (10.10.1731 – 24.02.1810). October 10 is his birthday.
Born in France, died in England. He had no academic degree, is a school dropout, yet he was a great scientist.
He made contributions to many branches of science. He accurately determined the proportions of gases in the air. The theory of electrical attraction and repulsion was his invention. He calculated the mass of the Earth, the famous Cavendish experiment. And the gas named hydrogen was discovered by him. Today, hydrogen is solving many crises on Earth.
Hydrogen is a very small, the smallest fundamental element. It has the least mass, meaning it is the lightest of all. At normal temperature, it is a gas. When the temperature is reduced greatly (to about -250°C), it becomes liquid. At even lower temperatures, it turns solid.
Solid, liquid, or gas, these are different states of the same substance depending on temperature. Water, for example, can be solid, liquid, or gas depending on heat. Many elements, or in short, elements, exist in gaseous form at normal temperature (around 37°C), like hydrogen. Air contains oxygen and nitrogen, which are gases at normal temperature. Carbon dioxide and methane are also gases at normal temperature, but they are not elements; they are compounds made from multiple elements.
Whether an element or a compound, many substances can exist as gases at normal temperature. And gases, though differing in chemical properties, molecular size, or structure, must still obey some common laws. For instance, gases are invisible; they cannot be seen with the eye. Yet, their presence can be sensed through pungent or pleasant smells, because gases easily spread in all directions. Gas molecules stick together with weak forces, unlike metals like gold, silver, or iron, where atoms form strong bonds with each other. The strength of these bonds varies from substance to substance.
Among solids, liquids, and gases, the molecules of gases hold onto each other with the weakest force. The strength, that is, the degree to which they stick together, varies for different gases like carbon dioxide, oxygen, or hydrogen, giving them different chemical properties. Still, as gases, they all follow certain common rules. Gas molecules move very rapidly, constantly colliding with one another within any confined space. When a molecule is hit, its speed increases; when it hits another, its speed decreases. This endless collision changes their velocities every instant. Even in such a complex state, scientists have been able to measure the average speed of gas molecules.
When the mass is greater, gas molecules move more slowly; their average speed decreases. The lighter and smaller a gas molecule, the faster it moves. This is why hydrogen, being the lightest and smallest, moves the fastest. When filled into a balloon, it makes the balloon rise into the sky. And when the temperature increases, their speed increases even more. In the case of hydrogen, the speed is so high that it escapes Earth’s atmosphere, overcoming the planet’s gravitational pull and drifts away into space.
Light gases such as hydrogen are not found freely in the Earth’s atmosphere. However, they are spread across nature in the form of compounds. The great storehouse of hydrogen on Earth is water. Hydrogen can be produced from the vast amounts of water in rivers and seas.
There are other ways to produce hydrogen. If you drop a piece of metal into hydrochloric acid, hydrogen bubbles out vigorously. Two hundred and fifty years ago, seeing such a reaction, the thirty-five-year-old English scientist Henry Cavendish said, “I have discovered a gas.” When the gas was discovered (1766), it was not named immediately. The naming happened seventeen years later. The French chemist Antoine Lavoisier named the gas “hydrogen.” What does that mean? Lavoisier said the words “hydro” and “gen” contain the meaning of the gas. The Greek word “hydro” means water and “gen” means to produce. That is, hydrogen is the water-maker — water-forming.
In two hundred and fifty years many changes have occurred in the history of the world. The history of science has also advanced by leaps and bounds. From hydrogen of atomic mass one to uranium of mass 238 we have learned about them. Knowledge of all the elemental substances on Earth is in human hands.
“HL-2M Tokamak.” Artificial sun.
Elements are made of atoms. Atoms are made of protons, neutrons, and electrons. Protons and neutrons are in the atom’s nucleus while electrons orbit around the nucleus. In the nucleus of the lightest hydrogen there is one proton and outside it one electron. Sometimes the nucleus may have one or two neutrons along with the proton. Then the mass changes to 2 or 3 and the name changes to deuterium (D) and radioactive tritium (T). There are other variants of the lightest hydrogen too: ortho-hydrogen and para-hydrogen. Without going into those, let us talk about the lightest element hydrogen.
Hydrogen is useful in many human activities. Plants, animals, and most compounds in the human body are made of hydrogen and carbon. Sixty percent of the human body is water. Without hydrogen water cannot be made. By combining hydrogen with nitrogen under pressure ammonia is produced. Ammonia’s compound, ammonium sulfate, is used on land as a fertilizer.
The virtues of the light gas hydrogen do not end there. Vehicles run with the help of hydrogen. How? Space rockets use hydrogen as fuel. The American space agency (NASA) has used hydrogen as rocket fuel for forty-five years. By producing energy from hydrogen, spacecraft achieve escape from Earth’s gravity and travel into space. India’s spacecraft reached Mars a few years ago (2014). Rockets or spacecraft do not use petrol or gasoline as fuel. They use hydrogen. That is, rockets or spacecraft burn hydrogen. How does this work?
In a closed system, when electricity is passed through water, water is produced (electrolysis is reversible: electricity can split water into hydrogen and oxygen, and in presence of electricity water forms). When hydrogen is burned in contact with oxygen, it produces pollution-free energy (heat) and water. The produced water is drunk by astronauts. And astronauts use the heat released by hydrogen combustion, converted into electricity, to perform many tasks. In the future the great need of the Earth is alternative energy. Coal and petroleum reserves are being depleted.
It is possible to produce alternative energy using hydrogen. Burning hydrogen will produce heat and water vapor; no toxic gases will be released into the air. In the future car fuel tanks will contain liquid hydrogen. Electricity will be generated from the heat produced by combustion in contact with air. Hydrogen-powered cars have become possible. Improved techniques for storing hydrogen in vehicle fuel tanks are being developed. Research on this topic is widespread around the world. India is not behind.
The tricks of the tiniest hydrogen do not end here. By using hydrogen in reactions, tremendous heat is produced inside the Sun. In the Sun and other stars, four hydrogen nuclei combine to form one helium nucleus, and intense heat is produced. The same process occurs in hydrogen bombs. When hydrogen nuclei fuse to form helium, enormous energy is released. Using this process China has created an “artificial sun.” Its name is “HL-2M Tokamak.” The artificial sun is actually a nuclear fusion reactor. It is a mechanical technique to produce energy from hydrogen (deuterium, tritium) by fusion. With its help tremendous temperatures will be produced (150 million degrees Celsius). Ten times hotter than the Sun. This device will be used to help meet shortages of electrical power. Other countries are also trying to produce energy by hydrogen fusion.
This energy can be used destructively, or for necessary, constructive work. It must be used for creative, not destructive, purposes to harness the tremendous power of the smallest element.
Reaction for producing energy from hydrogen
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