Why does CH4 have a higher vapor pressure at a given temperature than CH3Cl? Why does CH3OH have a higher vapor pressure at a given temperature than CH3CH2CH2OH? Why does H2CO have a higher vapor pressure at a given temperature than CH3OH?

Explanation:

CH4, methane is a non polar compound whereas CH3Cl is a polar compound because of presence of electronegative element chlorine. Hence, there is a net dipole moment in case of CH3Cl( Chloromethane). This causes CH3Cl to exhibits dipole-dipole intermolecular force of attraction, which is absent in CH4. Therefore, Chloromethane has a lower vapor pressure when compared to methane.  

it's filtration, but this is an assumption so my apologies if i got this

in 1783 cavendish was working with his hydrogen gas and found that when he burned it and condensed the vapor it was water. this was very significant since it disproved the greek theory of elements completely since water was not a simple substance but the product of two gases. it was lavoisier who hearing of the experiment gave cavendish's gas the name hydrogen ("water-producer") and added that hydrogen burned by combining with oxygen and that water was a hydrogen-oxygen combination.

explanation: