Why is cyclohexane liquid at room temperature?
Cyclohexane is a liquid at room temperature because its molecules do not have enough energy to escape into the vapour phase.
Cyclohexane contains only nonpolar C-C and C-H bonds.
The only intermolecular forces are London dispersion forces.
These are weak forces, but there are enough of them so that at room temperature the molecules are attracted to each other strongly enough to make cyclohexane a liquid.
The molecules can slide past each other but not get into the gas phase.
At about 81 °C, the molecules have enough energy to escape from each other, and the liquid begins to boil.