1. Introduce lesson and show students the essential question attached below. (Standard may be stated if school does not use an essential question.)

2. Ask students what they know about right angles. Discuss and write students responses on the chart.

3. Display page with examples of angles. Go through each example and have students to tell whether it is right angle or not. Have students justify why they think it is. Ask, “How can you tell?; Is there a way we can check? Is there a tool that we can use to check?” Review using a protractor as a tool. Make sure students know the symbol that indicates a right angle. (The square at the vertex of the angle.)

4. Ask students to discuss and record what perpendicular lines are on the response chart. Tell students they will learn more about them today in the lesson.

5. Discuss what they notice about right angles and perpendicular lines.

6. Display page with examples of perpendicular lines. Go through each example. Have students to tell whether the example has perpendicular lines or not. Students must explain how they know. If students are not sure, wait until after activity to readdress. Ask students if they see any examples of parallel lines.

7. Tell students perpendicular lines do not necessarily cross. Discuss with students that lines can still be perpendicular even if they do not extend or cross each other. (For example, a right angle is perpendicular rays that show only a portion of a full line.) Students can have a misconception about this since all of the line is not seen. Show the ‘extension’ of the line as dotted. Discuss this with students.

8. Tell students for today’s activity, they will use an index card to check for right angles. This might be a good time to talk about how it might be harder to physically check for right angles in the room with a protractor. Show students an index card and ask if they think there are any right angles in the index card. Use the protractor on the page to check and prove that there are actually 4 right angles.

9. Next, model for students how to use index card to check items. Make a point that it does not matter how big or small the object is, the angle measurement is the same. Teacher may need to discuss how objects with curved corners are not angles they should check.

10. Explain to students that they will work in pairs using the index card to look for and check for perpendicular lines in the classroom. Put students in pairs and distribute an index card and and handout on Perpendicular Lines in our classroom. Tell students they will work together, but they will record on their own sheet. Suggest to students they should try to find different objects from the rest of the class if possible and that it is ok if they check some objects that the think may not have perpendicular lines.

11. Tell students to pause silently for 30 seconds and to look around the room before they begin. Dismiss students to explore classroom. Teacher should circulate while students explore. Make sure students are on task, give direction, and assess if students seem to know what they are looking for.

12. Regroup as a class. Allow each pair of students to share one object they explored Write their findings on the interactive whiteboard. As students share, ask students, "How did you decide to check a particular object?; Did any of your objects have perpendicular lines that only showed rays of an angle?; Did you learn anything about perpendicular lines that we can add to the chart we started at the beginning of the lesson?"

13. Students should keep handout as a study reference.

14. Have students complete exit card.