Question
A physicist makes a cup of instant coffee and notices that, as the coffee cools, its level drops 3.00 mm in the glass cup. Show that this decrease cannot be due to thermal contraction by calculating the decrease in level if the $350 \textrm{ cm}^3$ of coffee is in a 7.00-cm-diameter cup and decreases in temperature from $95.0^\circ\textrm{C}$ to $45.0^\circ\textrm{C}$ (Most of the drop in level is actually due to escaping bubbles of air.)

Only $0.832 \textrm{ mm}$ of the drop is accounted for by thermal contraction, leaving $2.17 \textrm{ mm}$ resulting from air bubbles leaving the coffee.

Solution Video