Question

You pour coffee into an unlidded cup, intending to drink it 5 minutes later. You can add cream when you pour the cup or right before you drink it. (The cream is at the same temperature either way. Assume that the cream and coffee come into thermal equilibrium with each other very quickly.) Which way will give you hotter coffee? What feature of this question is different from the previous one?

(a) Adding cream later gives hotter coffee
(b) Adding cream earlier gives hotter coffee
(c) Both options result in the same temperature
(d) Adding cream earlier is not practical

Answer 1

Adding cream later gives hotter coffee as heat spontaneously flows from the hotter object to the colder one, resulting in a more uniform distribution of thermal energy.

Step-by-step explanation:

The way to obtain hotter coffee is by adding cream later, right before you drink it. This is because heat will spontaneously flow from the hotter object to the colder one, resulting in a more uniform distribution of thermal energy as the cream and coffee come into thermal equilibrium with each other quickly.

By adding cream later, the coffee will retain more of its original heat compared to adding cream earlier.