Final answer:
Outer planets differ from inner planets in size, composition, with outer planets being larger and having thick layers of gases, and their moons generally containing more ice.
Step-by-step explanation:
The outer planets differ from the inner planets primarily in three major ways: First, outer planets are much larger in size compared to the mostly smaller, rocky inner planets. Second, they have a different chemical composition; outer planets have dense cores surrounded by thick layers of hydrogen and helium, whereas inner planets consist mostly of rocks and metals. Lastly, the moons of the outer planets are generally composed of larger quantities of frozen ice, unlike the Moon, which resembles the composition of terrestrial planets.