A teaching laboratory experiment is described that uses Archimedes’ principle to precisely
investigate the effect of global warming on the oceans. A large component of sea level rise is due
to the increase in the volume of water due to the decrease in water density with increasing
temperature. Water close to 0 °C is placed in a beaker and a glass marble hung from an electronic
balance immersed in the water. As the water warms, the weight of the marble increases as the water
is less buoyant due to the decrease in density. In the experiment performed in this paper a balance
with a precision of 0.1 mg was used with a marble 40.0 cm 3 and mass of 99.3 g, yielding water
density measurements with an average error of −0.008 ± 0.011%.