A classic question that comes up among coffee drinkers is, “If you are going to add cream to coffee, is it better to add the cream immediately, or wait until later, assuming the goal is to have the coffee cool enough to be ready to drink as soon as possible?”

Have your students predict and then try it. Despite the fact that we added the cream early, on the cooler of the two cups, that cup came out hottest at the end of the experiment. This is a great demonstration of Newton’s law of cooling.

Temperature vs. time for the two cups of coffee

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