Ethanol has a higher boiling point than ethanal.

Ethanol can hydrogen bond with other ethanol molecules due to the -OH group. Ethanal molecules interact with each other through weaker permanent dipole-dipole interactions and Van der Waals forces. More energy is required to break hydrogen bonds than the forces between ethanal molecules.

Both ethanal and ethanol are soluble in water. While ethanal cannot form hydrogen bonds between ethanal molecules, it can hydrogen bond with water molecules due to the oxygen atom having a lone pair. Ethanol can also hydrogen bond due to the -OH functional group. Ethanol is slightly more soluble in water because it can form more effective hydrogen bonds.

Butanal has a higher boiling point.

Both molecules are polar and have permanent dipole-dipole interactions. However, as butanal is a larger molecule, it has more electrons and a larger surface area, resulting in significantly stronger Van der Waals forces between molecules.

Ethanal is more soluble in water.

This is because butanal has a much larger non-polar hydrocarbon chain (hydrophobic tail). When butanal dissolves, the hydrogen bonds between water molecules must be broken and replaced largely by weaker Van der Waals forces with the hydrocarbon chain. This process is energetically less favourable for the larger molecule.

Propanone has a slightly higher boiling point than propanal.

They both interact via Van der Waals forces and permanent dipole-dipole interactions. However, the permanent dipole-dipole interactions are marginally stronger in propanone.

Reason: The positive inductive effect of the alkyl groups. Alkyl groups push electrons towards the carbonyl carbon. Propanone has two alkyl groups (compared to one in propanal) stabilizing the partial positive charge on the carbon and making the oxygen slightly more negative. This results in a slightly more polar bond.

Both molecules are soluble in water due to hydrogen bonding between the carbonyl oxygen and water molecules. As propanone is slightly more polar (see above), the oxygen atom can form slightly stronger hydrogen bonds with water, making it very soluble.