Science Puzzle
Which Cools Faster, the Big Mug or the Small Cup?
Two coffees are poured from the same pot at the same moment: one into a big 400 ml mug, one into a tiny 60 ml espresso cup. Both start at exactly the same temperature.
Ten minutes later, which drink is cooler, and why?
The Answer
The espresso, every time. Heat can only leave a drink through its surfaces: the open top, the walls of the cup. The smaller the body of liquid, the more surface it has for every millilitre inside it, so a small drink sheds its heat far faster than a large one.
This is why a single chip goes cold on your plate while the baked potato next to it stays scalding, and it is the same reason small animals like mice must eat almost constantly to replace lost body heat while an elephant barely notices a cold morning.
The principle: Surface area to volume ratio. As an object gets smaller, its surface area shrinks more slowly than its volume, so small objects exchange heat with their surroundings proportionally faster than large ones.