High melting and boiling points are not characteristic of petroleum as a whole, but rather depend on the specific fractions within crude oil. Lighter fractions, like petrol, are highly volatile with low melting and boiling points, while heavier fractions, such as diesel and kerosene, exhibit higher melting and boiling points due to lower volatility. The variation in boiling points among these fractions is crucial for the process of fractional distillation, which separates crude oil into its components. ASTM D 86 is referenced for understanding distillation curves of petroleum products. Overall, the properties of melting and boiling points in petroleum are closely tied to the specific fractions present.