A very fresh egg, placed in water, will lie on the bottom. A week-old egg will lie on the bottom but bob slightly. An egg that is around three weeks old will balance on its small end, with the large end up. And a bad egg will float.
You can screw a Mason jar onto a blender! The blade part is screwed tightly to the lid, so you just pull the entire thing, blade, jar and all out of the base unit. Then tip it so the blade is on top and unscrew it.