What are oxidising agents ?

While cooking, if the bottom of the vessel is getting blackened on the outside, it means that

What would be the electron dot structure of a molecule of sulphur which is made up of eight atoms of sulphur ? 

How many structural isomers can you draw for pentane ?

How would you name the following compounds ?

$(i)$ $CH _{3}- CH _{2}- Br$

$(ii)$ $\begin{matrix}
   H  \\
   |  \\
   H-C=O  \\
\end{matrix}$

$(iii)$ $\begin{matrix}
   \begin{matrix}
   H\,\,\,\,\,H\,\,\,\,\,\,\,H\,\,\,\,\,H\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \,\, \\
   |\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
\end{matrix}  \\
   H-C-C-C-C-C\equiv C-H  \\
   \,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\
   H\,\,\,\,\,\,\,H\,\,\,\,\,\,\,H\,\,\,\,\,H\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \\
\end{matrix}$

Why are carbon and its compounds used as fuels for most applications ?