Briefly explain why the bulk temperature of the water remains low (at room temperature)

If the humidity of the room is low, the water that contacts the air directly could evaporate and takes some energy from the bulk thus decreasing its temperature steadily. This allows the water to have a lower temperature.

If the container has heat insulation, the rate of temperature drops will decrease too. Water specific heat is higher than the air, so it will need much more energy to increase water temperature. 

You use the atomic number to find out how many protons and neutrons there are in the atom. you use the atomic mass to find out how many protons and electrons there are in the atom.