Yes, you need a very clear purpose for chapter 3. I think you should treat that chapter like a separate book. Because textbooks are different from other non-fiction books, you should treat the chapters like individual books.
Also, I activated a chapter from a book which had completely different topics. I also had problems activating it, but Photoread4me told me to set a very clear purpose. I did that and it was easier to activate. I also asked myself very specific questions. This directed my reading and the book was easier to activate.
-Jason
