This is Concepts and Challenges in Science No. 1.

These texts are principle based, giving an excellent presentation of the concepts introduced. They combine foundational, and important, information with a format that encourages independent work. The questions in blue after each paragraph are all questions about the main point of the previous paragraph. Answering these questions consistently helps the student learn what a topic sentence is, and how to recognize it. The text accomplishes many goals and yet a lesson is able to be completed in 20 minutes.   

Sample pages can be viewed here.