Chemicals that penetrate the skin are usually what form that contacted it?

Chemicals that penetrate the skin typically do so in liquid form because liquids can seamlessly spread over the surface of the skin, allowing for absorption through the epidermis and into the underlying layers. The liquid state facilitates the direct contact with skin cells, which can absorb the chemical more readily compared to solids or gases.

While gases can exist in a gaseous state, their absorption generally requires a different mechanism, such as inhalation, or they must condense into a liquid to interact with the skin effectively. Solids, on the other hand, face limitations due to their physical state; they usually need to be dissolved in a liquid or transformed into a powder that can assist in penetration.

Therefore, liquids stand out as the primary form of chemicals that can effectively penetrate the skin, making this answer the most accurate choice in the context of skin absorption of chemicals.