Gravity separation is effective in distinguishing which types of materials?

Gravity separation is a process that relies on the differences in density between materials to separate them. This method is particularly effective in distinguishing heavy metals from lighter materials because it takes advantage of the gravitational force to separate components based on their weight. Heavier materials, such as metals, will settle to the bottom, while lighter materials will remain suspended or float, allowing for a clear separation.

In the context of the other options, while solid metals and liquids can be separated, gravity separation is not the ideal method for such a process because the different states of matter (solid vs. liquid) behave differently under gravity. Similarly, gaseous compounds cannot be effectively separated from solids using gravity separation, as gas does not have a fixed volume and its density differs greatly from that of solid materials. Lastly, while gravity separation can be used for plastics, it is typically less effective than other techniques, such as flotation or mechanical sorting, due to the minor density differences among the various types of plastics. Thus, gravity separation is most effective with heavy metals and lighter materials.