What is the difference between condensation and accretion? a. A particle grows by condensation when it adds matter from a surrounding gas. Accretion is the sticking together of solid particles. b. A particle grows by condensation when it adds matter from a surrounding gas. Separation of materials according to various density is called accretion. c. Condensation is the process when gas transforms into the solid phase without the liquid phase. Separation of materials according to various density is called accretion. d. Condensation is the process when gas transforms into the solid phase without the liquid phase. Accretion is the sticking together of solid particles.