This document discusses the difference between the words "if" and "when" and provides examples of their usage. "If" refers to possibility, while "when" refers to time. Some examples are given such as "I drink hot vinegar with honey if I get a really bad cold" and "I do not take anything when I have a cold." The document then provides more examples of using "if" and "when" in sentences about common illnesses and situations. Students are assigned an activity where they write sentences using "if" and "when" about what they do when sick and ask classmates questions using "if" about what they would do in certain situations.