Question: Why are the smaller rock planets nearer the sun and the larger gas planets further from the sun?

Jess Wade answered on 22 Jun 2015:

When the solar system formed a cloud of gas collapsed in on itself and the material started to collide and stick together, forming big clumps that hit in to other clumps and get bigger and bigger. All of the planets form like this, but close to the sun the temperature is so high that the gas planets wouldn’t condense. Only the materials with higher melting points and densities can, and so here the big heavy planets form. The gas gas giants form far enough away from the sun for cool temperatures so the gases can condense to form planets.