We kicked off the lesson with an entry task focused on why we use fossil fuel combustion (to produce energy).  Students were then asked to consider one unintended consequence of fossil fuel combustion (releasing carbon dioxide into the atmosphere).  We followed that discussion with a video about ocean acidification (below) before concluding the lesson with an experiment in which students re-created the conditions of ocean acidification by measuring the change in pH after exhaling through a straw placed in water for one minute.