How potential energy changes when you pull a magnet off a refrigerator door

The potential energy increase.

Explanation:

Potential energy is the energy stored within a physical system. Energy is the ability to do work or cause movement.  A free system acts in the way that minimizes the potential energy, so when you pull a magnet off a refrigerator door you are increasing the potential energy of the system because now if you allow the magnet to move freely, it will snap the door to minimize PE.

the dependant variable is spilled water

the independent is the heat