  Molecular clouds (MCs) in galaxies are complex places with many phases. It
is, therefore, essential to study the physics and kinematics of the MCs using
multiple emission lines. We probe the physics of the molecular gas and dust in
the nearby spiral galaxy NGC 7331 using multiple emission lines, i.e. carbon
monoxide (CO), 24{\mu}m and far-ultraviolet (FUV) data. 14 positions were
targeted across the gaseous disc of NGC 7331. We found that CO intensities, gas
mass, gas surface density, and 24{\mu}m-to-FUV flux ratio (i.e. the extinction)
increase up to about 40 arcsec from the centre and then start to decrease.
There is a positive correlation between most of the pair of parameters studied
(except FUV flux density). The beam-averaged physical parameters on the eastern
side of the disc show higher median values than those on the western side. Our
results indicate that the star formation activity, stellar populations and
overall physical properties of the ISM are different on either side of the
disc. Our study provides notable insights into the complex nature of the
interstellar medium (ISM) in galaxies and has the potential to provoke future
higher-resolution studies yet to come.
