Learning Objective: To study how molecular weight, molecular shape, functional group, and carbon number impact density.
Skill Level - Intermediate
Prerequisites:
Common names of alkanes
Chapter: Physical Properties
Sub-topic: Density
Author's Note: For any fire hazard or oil spill, understanding the nature of the substance is imperative for taking corrective actions. One such property is density, which measures how heavy or light any substance is when compared to water. In other words, whether it will sink or float. It also tells how compactly packed the substance is. More compactness means more molecules in a given volume thereby increasing its density. This section covers how we can predict the changes in density based on shape, molecular weight, and carbon numbers. We can also see how some functional groups significantly increase density in compounds containing the same carbon numbers.
Physical Properties - Density
Density refers to mass per unit volume of a substance; in other words, density measures compactness in a particular volume.
Long linear molecules pack more tightly, leading to more molecules in a given volume. Branched-chain molecules disrupt the close packing and, therefore, usually have lower densities compared to straight-chain molecules with the same number of carbons.
Almost all alkanes have densities of....
Smaller alkanes from C1-C4 are ....
Density, however, significantly increases when....
