As teachers we need to lay it out and show students exactly what we expect from them. So when assigning students a social studies essay to write, we should give examples of expository writing. Expository writing is writing to show knowledge of a topic. An example of expository writing that students encounter almost daily is the text in a social studies or science textbook, newspaper articles, magazines etc. They read these to gain knowledge on a topic. They read to learn. So that means that expository writing is writing to teach. They need to tell their audience what they are going to write about, write about it, and then tell the audience what they just told them. Expository writing is allowed to be “dry”. It is not there to entertain, but to educate. When writing a social studies essay, they are showing their knowledge. They need to assume that their audience knows nothing about the subject, which will help them elaborate on the subject they are writing about. Elaboration is explaining in detail or giving examples. They are backing up what they know and showing how they know it. Persuasion can also be involved in an expository essay especially in social studies. In that case, while they are elaborating they are backing up their opinion on the matter. Expository writing can also involve cause and effect, question and answer, comparison, sequence, description (Tompkins). It is the most widely used form of writing in adulthood due to the fact that businesses and services all need reports done.
http://www.teacherspayteachers.com/Product/Leveled-Expository-Writing-System-867302 offers an expository scaffolded/leveled/tiered writing system engine that helps social studies teachers create up to nine different ability levels for their students, all on the same topic, in about 5 minutes.