[Gauss44]

Is a coffee cup calorimeter usually considered to be an open system or a closed system?  Why?

I could understand this going either way.  Thanks.

(FYI - If it's an issue on this forum, this is NOT a homework question.  I am independently preparing for a graduate school entrance exam and have been out of school for many years.)

[SinkingTako]

I guess if you're preparing for exams it's usually considered a closed system because it's a calorimeter and technically there shouldn't be any transfer of heat between what's in the cup and surroundings. 

But well you know it's not perfect and there is a lot of heat loss to the surroundings etc, and water vapour can evaporate etc, so it's actually an open system in practice.