Thermodynamic databases for pure substances are lists of information about different materials and how they will react when heated or cooled. This data helps scientists and engineers to better understand how materials can be used for different purposes. For example, if you wanted to design a cooling system for a car, you would need to know the exact temperature and pressure at which different materials change and at which point they start to break down. This data is stored in these databases, and they can be used to help come up with the best solutions for a variety of purposes.