Coal oil

Coal oil is a liquid that is made by heating up coal. When you heat coal in a certain way, it turns into a gas, which can be condensed into a liquid. This liquid is called coal oil.

Coal oil used to be used as a source of light before electricity was invented. People would put coal oil into lamps and light them up. This would create a bright light that they could use to see in the dark.

Coal oil is also used as a fuel for engines and heaters. It is similar to diesel fuel, but it is made from coal instead of crude oil.

However, coal oil is not very commonly used anymore because it is not as efficient or clean as other types of fuel. Burning coal oil can release harmful pollutants into the air, which can cause health problems and damage the environment.

In summary, coal oil is a liquid fuel that is made by heating up coal. It was used as a source of light and fuel for engines and heaters before electricity and other types of fuel became more common. However, it is not very efficient or clean and is not used much anymore.