Why and how do density and buoyancy work? What is happening to the molecules? Why do things sink or float? What is so special about water? Can all things float? Sink? Does the PHASE of the matter, matter??

If you can, please answer in an informative paragraph form. Please and Thank you!!

All substances are made from some 100 different types of atoms, which combine with one another in various ways. Atoms form molecules that range in size from two to thousands of atoms. Pure substances are made from a single type of atom or molecule. Each pure substance has characteristic physical and chemical properties – for any bulk quantity under given conditions – that can be used to identify it. Gases and liquids are made of molecules or inert atoms that are moving about relative to each other. In a liquid, the molecules are constantly in contact with each other; in a gas, they are widely spaced except when they happen to collide. In a solid, atoms are closely spaced and vibrate in position but do not change relative locations. Solids may be formed from molecules, or they may be extended structures with repeating subunits (e.g., crystals). The changes of state that occur with variations in temperature or pressure can be described and predicted using these models of matter.

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