Which of the following procedures involves a physical change in one of the substances?

Question

separating an oil from solution by cooling it<--- my answer

allowing a nail to rust

creating salt by reacting sodium metal and chlorine gas

building a model rocket propelled by mixing baking soda and vinegar

Answer 1

I know I'm being picky about this and I think you have answered the question correctly but I want to point out some of what I consider flaws in answer D.
Building a model rocket is a physical process and mixing baking soda and vinegar is a physical process. It's only when the reaction starts that a chemical process begins. So I think the author of the questions fails this test.