What is the common name of propanone?

$C_{3}H_{6}$,$C_{4}H_{8}$,and $C_{5}H_{10}$ belong to the same homologous series.
$(i)$ Define homologous series.
$(ii)$ Why are the melting and boiling points of $C_{5}H_{10}$ higher than $C_{4}H_{8}$?
$(iii)$ Arrange these hydrocarbons in order of increasing boiling points.

The structural formula of ethyne is:

$(i)$ Distinguish between saturated hydrocarbons and unsaturated hydrocarbons with the help of the combustion process.
$(ii)$ Write the chemical names of $C_{4}H_{10}$ and $C_{2}H_{2}$ and draw their structures.

Mention four characteristics which change with increasing molecular mass in a homologous series.

Write the molecular formula of benzene and state the number of double bonds in its structure.