Explanation; The boiling points of alkanes increase as the number of carbon atoms in the molecule increases. This is due to an increase in the strength of the Van der Waals forces between the molecules.
As the number of carbon atoms in the molecule increases, the size of the molecule increases as well. This means that there are more electrons in the molecule, which results in stronger instantaneous dipole-induced dipole interactions between the molecules. Additionally, larger molecules have a larger surface area, which allows for more contact between molecules and thus stronger London dispersion forces.
Therefore, while the intermolecular forces holding the alkanes together are the same (Van der Waals forces), the strength of these forces increases as the size of the molecule increases, resulting in higher boiling points for larger alkanes.