What type of material is thought to explain the larger size of the outer planets relative to the inner planets?

Question

Quizplus · Accepted Answer

The larger size of the outer planets is thought to be due to the fact that they are composed mostly of gas and ice, while the inner planets are primarily made up of rock and metals. Ice is less dense than rock and metal, which allows for the accumulation of larger masses and sizes.

What Type of Material Is Thought to Explain the Larger