The same hot coffee was poured into two identical cups, 1 cup of coffee, 2 cups of coffee

The same hot coffee was poured into two identical cups, 1 cup of coffee, 2 cups of coffee with high fat cream. Which cup of coffee will cool faster?

Fat is less dense than the water that makes up coffee. Consequently, it will float up according to Archimedes’ law and cover the open surface of the coffee with a fatty film. This will prevent the free evaporation of liquid from the surface, and hence heat transfer with open air. Therefore, coffee with cream will cool more slowly than coffee without cream.