Question

The diagram shows the layers formed when 10 mL each of milk, soap water, and oil were slowly poured into a glass cylinder.

A plastic bead released gently into the cylinder settles on the layer separating the oil and soap water. What best compares the densities of the substances?

Milk is denser than the other liquids in the cylinder but not as dense as the bead.
Milk is denser than soap water, but the oil and the plastic bead are denser than milk.
The plastic bead is denser than soap water and milk, but oil is denser than the plastic bead.
The plastic bead is denser than oil, but milk and soap water are denser than the plastic bead.

Answer 1

Here the density of the substances are to be compared.

The denser the substance is, the more is the tendency to sink/stay at the bottom.

Here, from the figure, we see that, milk is at the bottom. So the milk is the densest.

Next is the layer of soap water, over which is the oil. So, soap water is denser than oil.

The bead sinks through the oil but stays over the soap water. So, bead is denser than oil but not as dense as soap water.

Arranging the given items in order of decreasing density, we have

Milk > Soap water > Bead > Oil

Hence the answer is

The plastic bead is denser than oil, but milk and soap water are denser than the plastic bead.