On Popper's Conjectures and Refutations (1963), the first three essays.
What is science, and how is it different than pseudo-science? From philosophy? Is philosophy just pseudo-science, or proto-science, or what? Popper thinks that all legitimate inquiry is about solving real problems, and scientific theories are those that are potentially falsifiable: they make definitely predictions about the world that, if these fail to be true, would show that the theory is false.
Looking for the full Citizen version?
The Partially Examined Life Philosophy Podcast