# When SiO2 changes state, what forces/bonds are being overcome/broken?

When silicon dioxide changes state, are the covalent bonds being broken (ie. the intramolecular forces) or is it the intermolecular forces?

• Intermolecular forces don't break – Akshar Gandhi Aug 22 '16 at 9:42
• The very words "intermolecular" and "intramolecular" don't quite apply to $\ce{SiO2}$. They imply it is made of molecules, which is not so. – Ivan Neretin Aug 22 '16 at 10:08

$\ce{SiO_2}$ is a network covalent compound that has an extremely high melting and boiling point, because many silicon-oxygen bonds have to be broken in order for it to achieve the necessary freedom. To clarify, SiO2, which has a tetrahedra network lattice formation, shows that each silicon is actually bonded to 4 oxygens; each oxygen is bonded to 2 silicon. These excess bonds aside from the ones of SiO2 are broken.