  Lava worlds are a potential emerging population of Super-Earths that are on
close-in orbits around their host stars with likely partially molten mantles.
To date, few studies address the impact of magma on the observed properties of
a planet. At ambient conditions magma is less dense than solid rock; however,
it is also more compressible with increasing pressure. Therefore, it is unclear
how large-scale magma oceans affect planet observables, such as bulk density.
We update ExoPlex, a thermodynamically self-consistent planet interior
software, to include anhydrous, hydrous (2.2 wt \% H_2O), and carbonated magmas
(5.2 wt\% CO_2). We find that Earth-like planets with magma oceans larger than
\sim 1.5 R_{\oplus} and \sim 3.2 M_{\oplus} are modestly denser than an
equivalent mass solid planet. From our model, three classes of mantle
structures emerge for magma ocean planets: (1) mantle magma ocean, (2) surface
magma ocean, and (3) one consisting of a surface magma ocean, solid rock layer,
and a basal magma ocean. The class of planets in which a basal magma ocean is
present may sequester dissolved volatiles on billion-year timescales, in which
a 4 M_{\oplus} mass planet can trap more than 130 times the mass of water than
in Earth's present-day oceans and 1000 times the carbon in the Earth's surface
and crust.
