Why do objects sink or float?
Actually, objects sink or float because their density is more or less than the density of whatever medium they are floating in. It does not have to be just water. This is an important distinction. For example, an iron screw will sink in water, but float in mercury. Anotehr example, an egg will sink in fresh water, but float in salt water. You can take a glass of salt water put the egg in and it will float, then pour some fresh water on top and the egg will appear to float in the middle fo the glass. If the floating object has a lower density than the medium it is in, it will float. If the object has a higher density it will sink.
