Re: Why are liquids non-compressible?

Liquids are considered to be slightly compressible.  Molecules in a liquid 
are held together by intermolecular forces.  They slide past one another 
freely.  As the molecules in liquids are compressed they begin to repel 
each other.  The compressibility of liquids and solids is somewhat 
negligible when compared to the compressibility of gasses.  Of course, 
liquids are more compressible than solids.

Glass is also a liquid because it does not a have a regular crystal 
structure and its molecules move past one another freely.

For additional information you may want to consult a general chemistry 
book. The reading on this topic will take you into many exciting areas of 
chemistry.  Enjoy!!

Note:  In many engineering applications it is assumed that liquids and 
solids are incompressible.