It has been documented that ________ can pass through the walls of plastic pipe even though the pipe is carrying water under pressure. This process by which molecules pass through this plastic pipe is called

• A. Inorganic compounds, Permeation
• B. Organic compounds, Filtration
• C. Organic compounds, Permeation
• D. Water Hardness, Diffusion

Answer: (C)

The situation tests how certain molecules move through plastic pipe walls even when water is under pressure. This movement is called permeation. In plastic materials, the wall acts as a semi-permeable barrier: molecules dissolve into the polymer on the inside surface, diffuse through the polymer matrix, and desorb on the outside. Organic compounds tend to permeate plastics much more readily than inorganic ions or water because they are more soluble in the polymer and can diffuse faster. So, when you have organic contaminants in contact with a plastic pipe, they can pass through the wall under the right conditions, potentially entering the water supply beyond the pipe wall. Filtration describes removal by a barrier, not the route of passage; diffusion is the general process but the specific term for passage through a solid barrier like plastic is permeation.