The main reason why h2co has a higher vapor pressure at a given temperature when compared to ch3oh is that h2co

Cannot form hydrogen bonds to its neighbours.

Explanation:

The strongest intermolecular forces in H₂CO are dipole-dipole attractions between the polar C=O bonds in nearby molecules.

The strongest intermolecular forces in CH₃OH are strong hydrogen bonding attractions between the O-H group in one molecule and the O atom in a nearby molecule.

Since H₂CO molecules have weaker intermolecular forces than methanol, more of them can escape from the liquid to the vapour phase.

Thus, CH₂O has a higher vapour pressure than methanol.

if you're asking what comes out, it's steam.