Yes, there is a rule in chemistry called the "pouring order rule" or the "density rule" that suggests pouring a heavier liquid into a lighter one. This rule is based on the principle that liquids with higher density tend to sink below liquids with lower density.
When pouring a heavier liquid into a lighter one, it helps prevent the formation of unstable layers or mixing difficulties. By pouring the heavier liquid first, it settles at the bottom of the container, creating a stable base. The lighter liquid is then poured on top, forming a distinct layer above the denser liquid.
This rule is particularly important when working with immiscible liquids, such as oil and water, where distinct layers can be observed. By following the pouring order rule, you can ensure a more stable and controlled layering of the liquids, minimizing mixing and facilitating subsequent manipulations or separations if needed.
It's worth noting that the pouring order rule is a general guideline, and there can be exceptions or specific cases where the order of pouring may differ based on the experimental requirements or the nature of the liquids involved.