Question

Sio2 is solid while co2 is gas

Answer 1

it is because the intermolecular forces between co2 are veryweak where as between sio2 it is strong 
due to this reason one is gas where as the other one is solid

Answer 2

" the only reason for the SiO₂ to be a solid and the CO₂ to be a gas is the internal molecular force between the atom "

⇒ the internal molecular force is more in SiO₂
⇒ the internal molecular force is less in CO₂

therefore SiO₂ is a solid and CO₂ is gas