Let's start by trying to understand what the question really means. What is the chemical structure of a molecule of "household oil" -- the quotes means you get to pick one that you look up and draw. Then, pick a "plastic" -- again, there are many. Compare the structures, and see if there's a similarity. Finding the reaction will be harder, but we have to see what's possible first. There is no chemical reaction, for example that will convert NaCl into H2O.