Is the first derivative of pressure with respect to specific volume always positive in a closed system?

In a closed system, the first derivative of pressure with respect to specific volume (∂P/∂V) is generally negative for most substances, especially in the context of ideal gases and liquids, reflecting that increasing specific volume (or decreasing density) typically results in lower pressure. However, in certain conditions, such as during phase changes or for specific materials, this relationship may not hold. Thus, it is not accurate to say that this derivative is always positive; it is usually negative or zero in typical scenariOS.