Darielis most likely used a process called cooling or condensation to slow down the molecules inside the sealed tank, causing the substance to change phase from gas to liquid. By cooling the substance, Darielis transferred energy from the gas molecules to the surroundings, which caused the molecules to slow down and come together to form a liquid. The process of cooling or condensation usually involves lowering the temperature of the substance or increasing the pressure inside the tank. This process is commonly used in chemistry and other scientific fields to change the phase of a substance and study its properties.