1. Why is it important to take the temperature of the closed system(the box) and the ice water before we start the demonstration?

It is important to take the temperature of your materials before you begin a demonstration so you can see the change in particle movement as you do the demonstration or after you finish.

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).