What is the state of molecules that have a molecular weight greater than 20?

Molecules with a molecular weight greater than 20 are typically found in a solid state at room temperature and atmospheric pressure. This is primarily due to the increased intermolecular forces present in larger molecules. As molecular weight increases, the van der Waals forces (and other intermolecular forces) become stronger, leading to more robust interactions between molecules.

In solids, molecules are closely packed together, which restricts their movement and gives solids a definite shape and volume. Conversely, smaller molecules with lower molecular weights can exist as gases or liquids at similar temperatures, owing to their weaker intermolecular forces that allow for more freedom of movement. Therefore, larger molecules, because of their higher molecular weight and the resulting stronger forces, are generally expected to be in a solid state under standard conditions.