Students will often all have different ideas about how the system and surroundings are separated from one another in the previous Ice calorimetry lab . While some things are obvious, the others are less so. Most students will put the water and ice in the system, and the outside of the cup in the surroundings, but almost everything else will be classified differently by each student. This is an excellent way to show that the classification is important, as it will change the calculations that need to be done later.