If lead and glass have the same volume do they displace the same amount of water?

Question

If lead and glass have the same volume do they displace the same amount of water?

Answer 1

Yes, if both are completely submerged.  No, if the glass is floating and the lead is submerged.  If an object is denser than water, the object sinks and the volume of water displaced is equal to the volume of the object.  If the object is less dense than water it will float.  The volume of water displaced is based on the weight of the floating object, not the volume of the object.   Both solid glass and solid lead are denser than water.  But a glass container with air inside may float.  

Answer 2

Glass is denser than water, and so is lead. Therefore, both glass and lead will sink, and equal volumes of lead and glass will displace equal volumes of water.

However, a glass bottle filled with air could be lighter than water, in which case it will float. An object which floats displaces its weight's worth in water, not its volume.

Hope that helps!