Why Did the Water's Temperature Increase Without Adding Heat?

[Benzoate]

Homework Statement

A cup containing 200 grams of H20 is siting on your dining room table . After carefully measuring its temperature to be 20 degree celsuis , y ou leave the room. Returning ten minutes later, you meaure its temperature again and find that it is now 25 degree celsuis. What can you conclude about the amount of heat added to water?(hint: this is a trick question)

Homework Equations

The Attempt at a Solution

My response to this question was that there is no heat added or heat is equal to zero since heat is a spontaneous process where heat flows from a hot object to a cold object. Even though there is a temperature difference involved in this process, The temperature increases rather than decreases.

 

[opuktun]

Ah, this is interesting...

I making a wild guess here.

Is it because ice (also H2O) in cup has melted?

If not, the question setter will say "200 g of water" instead of "200 g of H2O"

Hehe...