Liquids can remain separated in a jar because of differences in density. Density is a measure of mass per unit volume. The denser a liquid is, the more mass it has per unit volume.

When liquids with different densities are poured into a jar, the denser liquid will sink to the bottom, while the less dense liquid will float on top. This is because the denser liquid exerts more downward force on the less dense liquid than the less dense liquid exerts upward force on the denser liquid.

The following are four liquids with different densities that can be used to demonstrate this effect:

* Water: Density = 1 g/mL

* Vegetable oil: Density = 0.92 g/mL

* Honey: Density = 1.42 g/mL

* Mercury: Density = 13.6 g/mL

If these four liquids are poured into a jar, they will form distinct layers, with the mercury at the bottom, followed by the honey, the vegetable oil, and the water at the top. The colors of the liquids will remain separate, and they will not mix unless they are stirred or shaken.