Why does vinegar make an egg heavier?

Vinegar makes an egg heavier due to the process of osmosis. When an egg is placed in vinegar, the acetic acid in the vinegar reacts with the calcium carbonate in the eggshell, dissolving it and allowing the egg's contents to interact with the surrounding liquid. The egg absorbs some of the vinegar through the porous membrane, increasing its weight as water and acetic acid enter the egg. This process can cause the egg to swell and become heavier over time.