Which planets are known as the terrestrial planets? Which are known as the gas giants?
The terrestrial planets are Mercury, Venus, Earth and Mars.
The term terrestrial means Earth like. This really means that they are rocky planets. The inner four planets Mercury, Venus, Earth and Mars are all rocky and hence terrestrial planets.
The other terrestrial planets are not really Earth like. Mercury is much smaller and hotter. Venus is about the same size as Earth, but has a much hotter surface and atmosphere. Mars is smaller than Earth and has only a thin atmosphere and is colder.
A gas giant is a planet made primarily of hydrogen and helium. Jupiter and Saturn are both gas giants.
Uranus and Neptune are some times referred to as gas giants. In fact they are ice giants. An ice giant is a planet which contains ices which are usually hydrogen compounds such as water, methane and ammonia.