Easy exercises with 5 kg dumbells!?!

put the dumbells on the ground so that they are parallel to your body, and try doing pushups, i'm assuming they're circle ones...if you do a normal pushup, they'll slide out from under you, obviously you don't want that, so you'll have to squeeze your chest in to avoid this happening, which increases the workout significantly. Also, since the grip is sideways instead of a normal pushup, the workout is harder.

Do situps with these in your arms and rest them on your shoulders, then do situps or crunches, added weight...

one you don't even need them for is do a handstand against a wall (make sure you have plenty of room) then try to lower yourself down and push back up (basically military presses with your own body weight).

Have fun!