In this lab we will use 5-pennies to model water molecules sampled from each of 11 different “ice core layers” dating from the present to almost 500,000 years ago. The goal is to determine the temperature of climate in the past by comparing the average isotopic mass of the water molecules in the ice cores to the standard average isotopic mass of water from the ocean. Students will then compare their results to the 800,000 year ice core record.