In previous lessons, students identified and drew rays, lines, and segments. In this lesson, they turn their attention to lines that intersect, or cross, and those that never do.

In the first activity, students draw two kinds of quadrilaterals, one of which is a rectangle. The task motivates them to consider the relationship between lines—whether or not they would intersect at some point. Students are introduced to parallel lines in this context. Lines typically have arrows at both ends, which represent that they go on in each direction. In this unit, arrows are at the ends of lines when it is important that students distinguish lines from segments and other features.

In the second activity, students draw parallel and intersecting lines. They also practice constructing an argument for how they know that two lines are parallel (MP3). In an upcoming unit, students will classify shapes, based on whether they have parallel and perpendicular sides.

To support students with the new vocabulary in this lesson, consider making time for them to add to their “word wall” during the Lesson Synthesis. Allow a few minutes for students to add new terms, illustrations, and definitions in their own words to an organizer as shown in the blackline master.

In the next unit, students will analyze and categorize two-dimensional figures, based on whether they have parallel and perpendicular sides as attributes. How does this lesson prepare that upcoming work?