The first member of the aldehyde category is formaldehyde gas. Subsequent members of which the number of carbon atoms is up to 14, is a colorless liquid, the member having more than 14 carbon atoms is a colorless solid.
Formaldehyde, acetaldehyde and acetone are soluble in water. Water solubility of aldehydes and ketones decreases with increase in molecular weight
Aldehydes and ketones are lighter than water.
The boiling points of aldehydes and ketones increase with the increase of the molecular weight.
The smell of formaldehyde and acetaldehydes is strong and unpleasant. Higher aldehydes have a fruit-like odor. Fluid ketones have a sweet smell.