Why an egg sink in fresh water but float in salt water?
An egg sinks in fresh water but not in salt water because fresh water is not as dense. In order for something to float, the buoyant force has to be greater than or equal to the weight of the object. The buoyant force is equal to the weight of the liquid that is displaced by the object. To figure out the weight of the water displaced you multiply the density of the water by the volume and then multiply that by gravity. The density of the fresh water is less than the density of the salt water, therefore the weight of the water displaced will be greater in the case of the salt water, resulting in a greater buoyant force. The greater buoyant force allows the egg to float in the salt water.
