Perhaps the author of an article about whale conservation wants readers to feel sad about the plight of whales. Observe how purpose changes within a text.
Pull out statistics, images, facts, graphics, and other numbers to paint another picture of how the author is thinking. Have students pull out the names and titles of the people cited in an article. Persuasive text is used to persuade or convince the reader of something.
For example, if you know that an author is trying to persuade you, then, as a reader, you would want to be cautious about believing everything they tell you. Textbook authors write to educate. When you write with a certain purpose or intent, you also should be using specific word choice and stylistic elements to get your points across to your reader.
However, you need to think about the author's MAIN intent overall. Seek out stats.