What would you expect regarding the difference between U and H in physical and chemical processes? They will always be similar, although not quite the same. They will always be rather different. They will be similar for processes that only involve liquids and solids, but can be rather different for processes involving gases. They will be similar for processes that involve gases, but rather different for processes involving only liquids and solids.

What would you expect regarding the difference between U and H in physical and chemical processes? They will always be similar, although not quite the same. They will always be rather different. They will be similar for processes that only involve liquids and solids, but can be rather different for processes involving gases… …because pV can be large for processes involving gases! They will be similar for processes that involve gases, but rather different for processes involving only liquids and solids.