You stop for a cappuccino at a coffee shop and notice that the tiny white bubbles of steamed milk remain on the surface of the coffee. These air-filled bubbles stay where they are, rather than descending into the coffee or rising into the air, because they are
A) less dense than the coffee but more dense than the air above the coffee.
B) more dense than the coffee but less dense than the air above the coffee.
C) lighter than the cup of coffee but heavier than the column of air above the coffee.
D) thicker than the coffee but less thick than the air above the coffee.

Question

Quizplus · Accepted Answer

The tiny white bubbles of steamed milk remain on the surface of the coffee because they are less dense than the coffee but more dense than the air above the coffee. This density difference allows them to float on the coffee without rising into the air.

You Stop for a Cappuccino at a Coffee Shop and Notice