The vignettes and materials presented here will help you understand how the Possible Worlds resources can be integrated with your existing approach to these topics. They are intended to help you make connections between the core mechanics of the games and the phenomena related to common scientific misconceptions.
As the students play the game, they must make sure that the robot has enough fuel to perform all of his functions. Just like a plant, the robot makes his fuel (glucose) from carbon dioxide and water, and needs to be in a sunny spot to capture light energy. Like many organisms, the robot cannot use the light energy directly; it must cause the glucose to react with oxygen to produce carbon dioxide and water, thereby releasing the chemical energy for use in the process of cellular respiration.
Slides 4–15 describe the process of photosynthesis. They explain that it is the process that occurs in the leaves of green plants, using light energy to split water molecules, drawn through the roots, and carbon dioxide molecules, from the air, enabling the plant to produce sugar (glucose).
Most middle-school texts discuss the structure of leaves and how that relates to photosynthesis, which occurs in the leaves of green plants when they absorb light energy. The light energy splits carbon dioxide molecules from the atmosphere and water molecules drawn through the plant’s roots, enabling the plant to produce glucose; photosynthesis occurs in the presence of light. Some textbooks also explain that photosynthesis occurs in two stages: (1) the absorbed light splits water molecules to release oxygen and hydrogen atoms; (2) carbon dioxide is absorbed in the absence of light and reacts with the oxygen and hydrogen to produce glucose. Students may misunderstand the process and be left with one or more misconceptions—that plants perform only photosynthesis but not respiration, that photosynthesis occurs all the time, or that energy is produced during photosynthesis.
During gameplay, students will notice that the robot has to extract energy from the glucose by reacting it with oxygen in the air. The robot needs to extract this energy, from time to time, regardless of where he is or what he is doing. This is very much like the process of cellular respiration that occurs in plants—and all other organisms—at all times, and does not need light energy to occur.
Slides 16–20 describe the process of respiration, that it is the process of reacting glucose with oxygen to produce water and carbon dioxide with the release of energy. The slides explain that it is the opposite of photosynthesis, and that plants perform respiration all the time.
Generally, a page or two of text is devoted to explaining how respiration produces energy from glucose: Energy is released when glucose combines with oxygen to produce carbon dioxide and water, and is used to perform all the plant’s cellular functions. Some textbooks add that respiration occurs in all cells all the time, but when this is not explicitly stated students may develop the mistaken idea that respiration does not occur during daylight. Other misconceptions may be that respiration is the production of glucose, or that respiration occurs only in the plant’s roots. (The latter misconception is not addressed in the game.)
Students playing the game will observe that the robot is able to make all the materials he needs (glucose, methanol, and tear gas). Ultimately, all these materials are made from the basic building blocks of carbon dioxide and water. This mirrors how plants generate the vast majority of their raw materials: by using photosynthesis to create glucose, which they then use for energy and as a building block for nearly all the materials they need to survive.
Slide 15 explains that the glucose produced in photosynthesis is used to make all the materials the plants need to grow and thrive.
Most textbooks cover the raw materials plants require to survive and grow: carbon dioxide absorbed through the leaves, water and inorganic nutrients absorbed through the roots, and glucose. Some texts explicitly say that green plants make all the materials necessary for growth from the carbon dioxide and water they take in. In spite of this, one common misconception is that plants grow by sucking up soil through their roots.
By using the molecule-building activities, students will observe that all the materials the robot uses are made by reorganizing the atoms among different molecules. This mirrors the process of chemical change, where new substances are created by breaking bonds in molecules and reattaching the atoms in a new set of structures. This reinforces the concept that new materials do not simply “appear,” they are created from other chemicals by chemical change.
Slides 10–12 explain the chemical changes that occur during photosynthesis and describe the rearrangement of atoms during the process. Slide 14 shows the chemical equation that represents photosynthesis. Slide 17 compares photosynthesis to respiration and shows that they are opposites. Slides 18 and 20 explain the chemical changes that occur during respiration and describe the rearrangement of atoms during the process.
Textbooks usually mention chemical change as part of the discussion of photosynthesis and respiration. Some texts discuss that the processes of photosynthesis and respiration are opposite reactions. Students may mistakenly think that carbon dioxide and water produce glucose and energy, not understanding that, in order to produce energy, glucose must combine with oxygen.