Liquid oxygen

This is a pale blue liquid.

It is the air we breathe. It is very, very cold. This liquid can even float near a magnet.

It is used in big rockets. The liquid helps the rockets fly. It is also used in hospitals. People use it to help them breathe. It is a very useful thing.

Liquid oxygen is a clear, pale cyan liquid.

It is the liquid form of the oxygen in our air. This liquid is very cold. It stays liquid only at very low temperatures. Its boiling point is -183 °C.

This liquid has a special trait called paramagnetism. This means it is drawn to magnets. You can even see it float between magnet poles.

People use liquid oxygen for many jobs. It is used in hospitals to help people breathe. It is also used in many types of aircraft.

Rockets use it too. It acts as an oxidizer. An oxidizer helps things burn. This helps rocket engines make power. Robert H. Goddard used it in the first liquid-fueled rocket in 1926. Many rockets today still use it. This includes the Space Shuttle and many SpaceX rockets. Scientists get this liquid from the air. They use a way called fractional distillation. This process separates the gases in the air.

Liquid oxygen is a clear, pale cyan liquid.

It is the liquid form of the oxygen we breathe in the air. This liquid is a cryogenic substance, which means it is extremely cold. It has a freezing point of -218.8 °C and a boiling point of -183 °C. It is slightly denser than liquid water. One interesting thing is its expansion ratio of 1:861. This means it grows a lot when it turns back into a gas.

This liquid has a special trait called paramagnetism. This means it is drawn toward magnetic fields. You can actually see this happen in a lab. If you pour it between the poles of a strong horseshoe magnet, it stays suspended there.

Liquid oxygen is also a very powerful oxidizing agent. An oxidizer is something that helps things burn. Because it is so strong, organic materials will burn very fast in it. Even things like coal briquettes or asphalt can explode if they are soaked in it. This can happen from a tiny spark or even a light blow.

Scientists have worked hard to understand this liquid for a long time. In 1845, Michael Faraday liquefied many gases. However, oxygen was one of the "permanent gases" that resisted his attempts. Later, in 1877, Louis Paul Cailletet and Raoul Pictet made the first liquid air droplets. In 1883, Zygmunt Wróblewski and Karol Olszewski finally produced the first measurable amount of liquid oxygen.

Later, in 1924, Gilbert N. Lewis predicted a molecule called tetraoxygen to explain how the liquid acts around magnets.

Liquid oxygen is very important for space travel. It is the most common liquid oxidizer used to power spacecraft.

Robert H. Goddard used it in the first liquid-fueled rocket in 1926. Since then, many famous rockets have used it. The V-2 missile used it during World War II. The Apollo Saturn rockets and the Space Shuttle also used it. Today, many active rockets like the SpaceX Falcon 9 and the NASA Space Launch System use it too. Even the Chinese Long March family of rockets uses liquid oxygen.

We use this liquid for more than just rockets. It is an industrial gas used for medical and commercial jobs. It is used in hospitals to help people breathe. It is also used in some military and commercial aircraft. To get it, scientists use a method called fractional distillation. They use a special plant to separate the oxygen from the air. This helps us turn the invisible air around us into a useful liquid.

Liquid oxygen, often called LOX, is a clear, pale cyan liquid form of dioxygen. It is a cryogenic substance, which means it exists at extremely low temperatures. This liquid is vital for both modern technology and human life. It serves as a powerful oxidizer for rocket engines. It also provides a concentrated source of oxygen for medical and military use.

To understand how we get this liquid, we must look at the air around us. Scientists use a process called fractional distillation in cryogenic air separation plants. This method separates the oxygen from the natural air. Liquid oxygen has a density of 1.141 g/cm³, making it slightly denser than liquid water. It has a freezing point of -218.8 °C (54.4 K) and a boiling point of -183 °C (90 K). Because of its high expansion ratio of 1:861, it expands greatly when it turns into a gas.

One of the most fascinating properties of liquid oxygen is its paramagnetism. This means the liquid is attracted to magnetic fields. If you pour it between the poles of a powerful horseshoe magnet, it will stay suspended there. This behavior led Gilbert N. Lewis to predict the existence of the tetraoxygen molecule (O4) in 1924. He proposed this to explain why the liquid defied Curie's law. While modern computer simulations show that stable O4 molecules do not exist, they show that O2 molecules form transient O4 units by associating in pairs.

Liquid oxygen is also a very powerful oxidizing agent. An oxidizer is a substance that enables or accelerates combustion. Because it is so reactive, organic materials will burn very rapidly and energetically when they touch it. Some materials, such as coal briquettes or carbon black, can even detonate unpredictably if soaked in it. This can be caused by flames, sparks, or even the impact of light blows. Even petrochemicals like asphalt can show this dangerous behavior.

History shows us the long struggle to master these cold substances. By 1845, Michael Faraday had liquefied many known gases. However, oxygen was one of six "permanent gases" that resisted his attempts. In 1877, Louis Paul Cailletet and Raoul Pictet succeeded in producing the first droplets of liquid air. Finally, in 1883, Polish professors Zygmunt Wróblewski and Karol Olszewski produced the first measurable quantity of liquid oxygen. These discoveries paved the way for modern aerospace engineering.

Liquid oxygen is the most common cryogenic liquid oxidizer used for spacecraft propulsion. It is usually paired with fuels like liquid hydrogen, kerosene, or methane. Robert H. Goddard used it in the first liquid-fueled rocket in 1926. During World War II, the V-2 missile used it under the names A-Stoff and Sauerstoff. In the 1950s, the Redstone, Atlas, and R-7 Semyorka rockets all relied on it. Later, the Apollo Saturn rockets and the Space Shuttle main engines used LOX to reach orbit.

Today, liquid oxygen remains essential for global space programs. Many active rockets use it, including the SpaceX Falcon 9 and Starship. NASA uses it for the Space Launch System. The European Space Agency uses it for the Ariane 6. Many Chinese rockets, such as the Long March family, also use it. Other nations like India, Japan, Korea, and Russia continue to use LOX in their rocket systems.

Beyond space, liquid oxygen has critical roles in daily life. It is classified as an industrial gas for medical and commercial use. In hospitals, it is used to help patients breathe. The U.S. Air Force uses it for high-altitude aircraft flights. In 1985, the USAF even began building its own oxygen-generation facilities at major bases. This ensures a steady supply of oxygen for both breathing and strategic mission needs.