Can i swap memory modules between mac I have 3 mac's 


Mac Mini 2.4 GHz Core 2 Duo , 2GB 1067 MHz DDR3, 
Macbook pro (15", Early 2011), 2GHz Core i7, 4GB 1333 MHz DDR3
Macbook Air (13" Mid 2012), 2GHz Core i7, 8GB 1600 MHz DDR3


Is it possible to use 4GB memory modules from Macbook pro and put it in Mac mini, thus upgrading its memory size. 

If that works, then i was thinking to taking 8 GB memory module out of Macbook Air and put it in Macbook Pro. 

And finally get new 16 GB memory modules for Macbook Air. 

Considering that all of them require DDR3 , does clock speed cause any issues with working on macs.
No, this will not work. Only the RAM for the MacBook Pro and Mac Mini are compatible, as MacBook Airs have their RAM soldered to the logic board.

While you will be able to move the MacBook Pro memory to the Mac Mini, the speed would be slower. Because the RAM is soldered to the logic board of the MacBook Air, this memory can't be moved at all, so you'd still be short new memory.

If you want to upgrade your memory in both the Mac Mini and the MacBook Pro, move the sticks from the MBP to the Mini, then buy new ones for the MacBook Pro. If you just want the upgrade in the Mini, buy new sticks for the Mini's specs.