Final answer:
Too little heat in fractional distillation can lead to incomplete separation and impurities in the collected fractions.
Step-by-step explanation:
Fractional distillation is a process used to separate different components of a mixture based on their boiling points. In this process, the mixture is heated, and the components with lower boiling points will vaporize and rise to the top, while the components with higher boiling points remain at the bottom. If too little heat is used during fractional distillation, the temperature may not be high enough to vaporize all the components, leading to incomplete separation and the presence of impurities in the collected fractions. For example, if crude oil is not adequately heated during the distillation process, the heavier fractions such as diesel and gasoline may not fully vaporize, resulting in a lower quality product.