Atomic mass deals with the number of protons and neutrons added together, atomic number deals with protons only, though isotopes can be explained like this, say you had a hydrogen atom it's one proton and one electron if you add a neutron to it, the hydrogen becomes Deuterium which is a isotope of hydrogen it's the same atom just a neutron added to it for a different atomic mass if only slightly changed
Hi. Increased evaporation would be the greatest difference.
Explanation:
Have you ever had a drink in a mug with a lid? When you would remove the lid, all of the liquid on the lid is the liquid that would evaporate if there was no lid.