Copyright 1995-97 VirtualChaos. All Rights Reserved. Void where Prohibited. Let me take this opportunity to introduce the concept of buoyancy. Buoyancy is the tendency of an object to come to rest at the level where its internal pressure balances its external pressure.
Wood floats because the internal pressure of the water is higher than that of the wood.
Lead sinks for the same reason. This tendency is seen for every state of mass and energy. In classical mechanics this is called thermodynamics. Thermodynamics explains the properties of heat and how it affects mass. Heat is an energy level just under the octave we call light.