Final answer:
Methylene chloride will form the lower (bottom) layer when mixed with water because its density of 1.33 g/mL is higher than that of water.
Step-by-step explanation:
When methylene chloride is mixed with water, the organic phase that forms will be the lower (bottom) layer. This is because the density (d) of methylene chloride is 1.33 g/mL, which is greater than the density of water (approximately 1.00 g/mL). Substances with a higher density will sink below substances with a lower density, resulting in the more dense substance forming the bottom layer. This is a fundamental concept in liquid-liquid extraction processes, which are common in both organic chemistry labs and in various industrial applications where different density liquids are used to separate compounds.