Txtbk Question 4A.9

[Mia_Renna_1L]

Why is the heat lost by metal equal to the negative heat gained by water?

[705968973]

This is a classic example of heat lost and gained by system vs. surrounding. In the case of a metal being surrounded by water in a calorimeter, the metal represents the system whereas the water represents the surrounding. The heat lost by the system (metal) is q and the heat gained by the water (the surrounding) is -q. -smdeltat = smdeltat is a common equation used for these kinds of questions, where smdeltat is the heat lost by the system and -smdeltat is the heat gained by the surrounding.

[Richard Chiu 1I]

The above response does a great job help explain the question! I'd also want to add that this is an application of the First Law of Thermodynamics, where the energy is completely transferred from the metal (system) to the water (surroundings).