Calcium oxide

Quicklime is a white powder.

It comes from heating rocks or shells. This makes the powder. It is very useful.

When water touches it, it gets hot. This heat can warm up food. It can even break rocks.

People use it to make cement. This helps us build things. It also makes bright light for shows.

Quicklime is easy to find. It is used in many ways. It is a very busy powder!

Quicklime is a white, solid powder.

People also call it calcium oxide. It is a very useful material.

How is it made? People heat rocks like limestone in a hot kiln. This step is called calcination. The heat is very high. It must be over 825 °C. This heat lets out a gas called carbon dioxide. What is left behind is quicklime.

Quicklime is very busy. When it touches water, it gets very hot. This is an exothermic reaction, which means it gives off heat.

This heat can warm up food in a can. It can even help break rocks in a mine.

People use quicklime for many things. It is a key part of making cement. In the past, it was used to make bright light for plays. This was called limelight. It is also used to help clean air. It can take away bad gases from smoke. China makes the most quicklime in the world. They make about 170 million tonnes every year.

Quicklime has a special shape made of tiny parts.

Calcium oxide is a white, solid material.

Many people call it quicklime or burnt lime. It is a very important chemical compound. This substance is also known as an alkaline, caustic solid. It stays in a crystalline form at room temperature.

Quicklime is quite inexpensive to make. Because it is cheap, it is used as a commodity chemical. This means it is traded in very large amounts around the world.

Making quicklime is a step-by-step process called calcination.

First, people take materials like limestone or seashells. These materials contain calcium carbonate. Next, workers put them into a lime kiln. They heat the material to over 825 °C. This high heat causes a change called thermal decomposition. This change lets out a gas called carbon dioxide. After the gas leaves, the quicklime is left behind.

People have used this reaction for a very long time. It is one of the few chemical reactions known since prehistoric times.

Long ago, humans used limestone-based plaster for floors. This was seen in the Pre-Pottery Neolithic B period. These lime-ash floors were used until the late nineteenth century. Even ancient Romans used quicklime in their concrete. This helped their buildings last for many centuries. The quicklime helped fill cracks in the concrete over time.

Quicklime is used in many different ways today.

It is a key ingredient for making cement. In the past, it created bright light for theaters. This was called limelight, and it was used before electric lights. It can also be a food additive. It is used as a leavener and an acidity regulator. In the petroleum industry, it helps find water in fuel tanks. It can even help remove sulfur dioxide from exhaust gases.

Quicklime reacts in a very powerful way with water. This is called an exothermic reaction. This means it releases thermal energy or heat.

One litre of water can react with 3.1 kilograms of quicklime. This process creates a lot of heat very quickly. Some companies sell kits that use this heat to cook food. This works without needing an open flame. However, the reaction is so strong it can cause skin irritation. You must handle it with great care.

Calcium oxide is a white, crystalline solid that is also known as quicklime or burnt lime.

It is an alkaline and caustic compound, which means it can react strongly with other substances. Because it is relatively inexpensive to produce, it is considered an important commodity chemical. This means it is traded and used in massive quantities across many different global industries. Scientists also recognize calcium oxide as a distinct mineral species named "Lime."

This mineral belongs to an isometric crystal system and can form a solid solution series with a mineral called monteponite. However, quicklime is chemically unstable in moist air. It will quickly convert into portlandite, which is another form of calcium hydroxide.

To create quicklime, humans use a process called calcination or lime-burning.

This process begins with materials like limestone or seashells, which contain calcium carbonate. These materials are placed inside a lime kiln and heated to temperatures above 825 °C (1,517 °F). This intense heat causes thermal decomposition, a chemical change where the material breaks apart. During this reaction, a molecule of carbon dioxide gas is liberated and escapes. What remains in the kiln is the solid calcium oxide. This is one of the few chemical reactions that humans have known since prehistoric times.

Quicklime is highly reactive, especially when it meets water. When calcium oxide reacts with water, it undergoes an exothermic reaction, which means it releases thermal energy.

This specific reaction produces a chemical called calcium hydroxide. As the solid hydrates, it actually puffs up in size. The amount of energy released is quite significant; one litre of water combining with approximately 3.1 kilograms of quicklime produces 3.54 MJ of energy. This heat can be used for practical tasks, such as self-heating food cans or cooking without an open flame. However, this reaction is so vigorous that it can cause severe irritation or burns if it touches moist skin, eyes, or the respiratory tract.

Because of its unique properties, quicklime has many different industrial uses. It is a primary ingredient in the production of cement. In the petroleum industry, it is used in water detection pastes. These pastes mix calcium oxide with phenolphthalein, a chemical indicator. If water enters a fuel tank, the quicklime reacts to form calcium hydroxide. This raises the pH level enough to turn the phenolphthalein a vivid purplish-pink color, signaling the leak. Additionally, quicklime is used in chemical pulping to help regenerate sodium hydroxide. It is also used in flue-gas desulfurization to remove sulfur dioxide from exhaust streams.

History shows that quicklime has been vital to human construction for millennia. Archeological evidence shows that Pre-Pottery Neolithic B humans used limestone-based plaster for flooring. These lime-ash floors were used for many centuries until the late nineteenth century. Ancient Roman concrete is also famous for its durability, which is partly due to quicklime. When mixed using a "hot mixing" method, the quicklime creates small structures called lime clasts. If the concrete cracks, water enters and reacts with these clasts to create a calcium-saturated solution. This solution can recrystallize as calcium carbonate, effectively filling the cracks and repairing the structure.

Quicklime has even been used for light and warfare. Before the invention of electric lighting, people used "limelight" for theatrical productions. This was achieved by heating quicklime to 2,400 °C (4,350 °F), which caused it to emit an intense glow. In historical warfare, quicklime was sometimes used as a weapon. It is thought to have been a component of Greek fire, where it could raise temperatures above 150 °C (302 °F) to ignite fuel. Historian David Hume recorded that the English Navy used quicklime to blind an invading French fleet during the reign of Henry III.

Today, the scale of quicklime production is massive. The annual worldwide production is approximately 283 million tonnes. China is the largest producer in the world, creating about 170 million tonnes every year. The United States is the second largest producer, with roughly 20 million tonnes per year. While quicklime is powerful, there are several substitutes available depending on the job. Limestone is a much cheaper but less reactive alternative used in agriculture and sulfur removal. Other industries might use magnesium hydroxide for pH control or calcined gypsum for making plasters.