Fall is a great time of year to study the nutrient cycle. And with many of your students carving pumpkins, there will be no shortage of materials to observe. All you will need to start are a few pumpkins, cameras, CO2 and temperature sensors, and a convenient location for students to make observations of some decomposing pumpkins.
To tie this activity to the nutrient cycle, students will need to collect both qualitative and quantitative data. Over time students note how the pumpkins’ appearance changes. The use of sensors will provide empirical data that will help your students connect these changes with the process of decomposition. Students will also need to have a basic understanding of what carbon dioxide gas is.
Begin the investigation by having students record observations on the appearance of the pumpkins. Plan on having students make observations for three to six weeks. Taking pictures is recommended so students can track the change in appearance of the pumpkins over time. Photos that are taken two or three times a week can be used by students in presentations or can be compiled to create time-lapse videos. Classrooms that have iPads can use an app called iStopMotion to create the videos. Windows computers can use Movie Maker to create the videos. Likewise, Macintosh computers can use iMovie software.
Further integrate technology into this inquiry by using sensors. Start with a carbon dioxide sensor by placing pieces of pumpkin into a sample bottle. Follow the calibration procedure (before collecting data). It is also recommended to set the sample rate at 1/minute for this activity. The data below show that carbon dioxide is released from the pumpkin pieces at a constant rate.
Now the real fun begins! By using sensor data, your students are now beginning to see evidence that the pumpkins are decomposing. Encourage further inquiry by having your students design experiments that test additional variables. Questions such as these can help steer students toward interesting investigations:
- Does the temperature change during the process of decomposition?
- How does the presence or absence of light affect decomposition?
- What affect does water have on decomposition?
- How does the amount of oxygen change during decomposition?
- How does the mass of a decomposing pumpkin change over time?
Encourage the development of science and engineering practices by asking the lab groups to test different variables. This approach can be engaging for students, since they will have a choice about which variables they will test and what methods they will use when designing their experiments. It will also enrich the discussions students are having, as they will be interested in learning how the different variables affect their own results.
Conclusions should be based on data. The use of cameras and sensors is a practical way to provide data while integrating technology into this unit. Data from sensors and other measurements will help students confirm or refute predictions, ensuring that this unit will be both fun and impactful on their long-term understanding of these concepts.