Cooling a Cup of Coffee

Newton’s law of cooling

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Cooling rate is proportional to the temperature difference with the surroundings.
• So the difference decays exponentially: $T = T_{\text{room}} + (T_0 - T_{\text{room}})e^{-kt}$.
• To cool a drink fastest, add cold milk at the end.

Steps

1. The bigger the gap, the faster
2. Ten minutes later
3. Ready to drink
4. Milk now or later?
5. Check the milk
6. Halving the gap