demonstration, inquiry activity, photosynthesis, chemsitry education


Chemistry | Science and Mathematics Education


When asked what plants need for photosynthesis, many students can correctly recall the reaction equation and state that plants require CO2, H2O, and light. Many students, however, do not understand that these reactants are the raw materials plants use to make sugars and instead believe that they are food for plants. Moreover, when questioned further, students often voice the idea that plants get their food from the soil (Kestler 2014). This is consistent with findings that fewer than half of current middle and high school students have a correct understanding of the process of photosynthesis (AAAS 2015). We developed this lesson to help students confront their misconceptions about photosynthesis and what constitutes food for plants. Photosynthesis is a complex process that requires a unit of instruction including multiple student experiences. Therefore, we use this lesson as an introduction to the unit on matter and energy in organisms and ecosystems so that students develop a better understanding of the reactants of photosynthesis. We wanted students to investigate how different variables typically mistaken for plant food (e.g., CO2, H2O, light, soil) affect photosynthesis, with the goal of helping students develop an understanding that photosynthesis is a chemical process that produces food for plants. We modified a demonstration (Fox, Gaynor, and Shillcock 1999) that allows for an estimation of the rate of photosynthesis by timing how long it takes punched-out spinach-leaf disks to rise to the top of a solution due to the production of oxygen gas. In our modification, students perform the original demonstration in small groups and then develop their own follow-up investigations to explore the effects of other variables on the rate of photosynthesis, using the initial procedures as a model (see Online Supplemental Materials for a complete teacher guide).

Original Citation

Stevens, B., Rybczynski, S., & Herrington, D. (2016). Food and energy for all: Turning a demonstration into an inquiry activity! Science Scope, 40(4), 48-56