Which type of compound is formed,if one hydrogen of an alkane compound is substituted by a hydroxyl $[-OH]$ group?

The first member of the alkyne homologous series is:

What is the difference between two consecutive members in a homologous series of alkanes in terms of:
$(i)$ molecular mass.
$(ii)$ number of atoms of elements.

$A$ colourless gas '$X$' has a formula $C_{3}H_{6}$. It decolourises bromine water. Write the chemical name of '$X$'.

Which of the following is not a straight chain hydrocarbon?

$C_{3}H_{6}$,$C_{4}H_{8}$,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.