These are the feelings/emotion I would like to describe with a word:
You have been really a close friend of another person for many many years, and then you stopped hanging out together and even calling at telephone. Then you suddenly met at a party. You manage do to only small talk and nobody knows really what to say. There's a general embarrassment and you end up without speaking too much.
The opposite situation is when you meet at a party somebody who you weren't in touch with for so long, and both are more than happy to met, and it is as only a few days have passed since the last time.
How would you name these stuff?