The density increases to a local maxima as a function of time and attractive forces. There are claims of a global maxima, but these are often refuted by others claiming to have found a new global maxima.
The inverse of the function results in a decrease in density to a local minima as a function of time and repulsive forces.
Plain water. One time when I was young, I got thirsty and drank a lot of water straight from the tap. Then got sick and threw it all up. Now I have a hard time drinking plain water. I can drink water with flavor, I can drink water with food.
It's what plants crave!