Directions 1. Use the instructional model to show students where they are in the course of the unit. Show slide 2 of the 3.3 Observing Plants in the Light and Dark PPT. 2. (Day 1) Have students prepare for the plants in the light and dark investigation. Follow the instructions in Part A of the 3.3 Observing Plants in the Light and Dark Worksheet. Slide 3 of the 3.3 Observing Plants in the Light and Dark PPT has pictures of the setup for the investigation. Let students re-watch the first three minutes of the Carbon TIME Growing Plants Video. This part discusses the questions and shows the setup for the investigation. If you have multiple classes, each class can set up one or two 6.8 liter sealable plastic containers in the light and one or two 6.8 liter sealable plastic containers in the dark. Note: large sealable containers with room for the BTB and plants will do; the container does not need to be this exact size. If you have a single class, then each group of four students can set up one 6.8 liter sealable plastic container, with half the 6.8 liter sealable plastic containers going into the light and half going into the dark. 3. (Day 1) Leave the containers overnight. Leave the lights on for the 6.8 liter sealable plastic containers in the light. 4. (Day 2) Have students observe and record results. Each student should be responsible for observing one 6.8 liter sealable plastic container in the light and one 6.8 liter sealable plastic container in the dark and recording their observations in Part B of the 3.3 Observing Plants in the Light and Dark Worksheet. Show slide 4 to allow students to see the possible colors of BTB. Record results for all the containers on the 3.3 Observing Plants in the Light and Dark Class Results 11 x 17 Poster. 5. Have students compare data between groups and look for patterns. Show slide 5. Discuss the general patterns the class sees for all the containers, and have students record summaries of those patterns in Part C of the 3.3 Observing Plants in the Light and Dark Worksheet. (In the light, yellow BTB turns blue. In the dark, blue BTB turns yellow.) Show the second part of the Carbon TIME Growing Plants Video, after the first intermission where Darryl and Nina discuss the results of the Plants in the Light and Dark investigation (begin at about 2:30). Ask the class to compare their results to Darryl and Nina’s results, pausing the video when the data are shown. Ask students if they see the same patterns, any similarities and/or differences. Ask them why there may be similarities and/or differences. If your students’ plants in the light dark investigation fails to provide the expected BTB color changes (which could happen for a variety of reasons, including too much NaOH in the BTB or too high concentration of BTB), use the Carbon TIME Growing Plants Video to help them compare their results with the desired results. Use this as a starting point for a conversation and ask the students why the results are different. 6. Revisit predictions from the previous activity. Show slide 6. Ask students to retrieve their completed tools from the previous activity: 3.1 Predictions and Planning Tool for Plant Investigations. Have them compare the predictions they made with the results of the investigation. Which predictions were correct? Which predictions were incorrect? What questions do they still need to answer? Remind students that food is necessary for plants to be able to grow and move. Tell students that they will use the data that they collected here to help them to be able to explain two processes that relate to plants growing: photosynthesis and cellular respiration. 7. (Optional) Partially complete the Evidence-Based Argument tool. If you plan on teaching Lesson 4 while waiting for students’ radish plants to dry (see the Plants Unit Front Matter file for more information on making this choice), be sure to have students partially complete the 3.5 Evidence-Based Arguments Tool for Plants first. See Activity 3.5 for more guidance on completing this step. 8. Have students complete an exit ticket. Show slide 7 of the 3.3 Observing Plants in the Light and Dark PPT. Conclusions: What did you observe during the investigation? Predictions: What do you think happened to the CO2 that the plants absorbed in the light? On a sheet of paper or a sticky note, have students individually answer the exit ticket questions. Depending on time, you may have students answer both questions, assign students to answer a particular question, or let students choose one question to answer. Collect and review the answers. The conclusions question will provide you with information about what your students are taking away from the activity. Student answers to the conclusions question can be used on the Driving Questions Board (if you are using one). The predictions question allows students to begin thinking about the next activity and allows you to assess their current ideas as you prepare for the next activity. Student answers to the predictions question can be used as a lead into the next activity.