Activity 4.3: Molecular Models for Potatoes Making Food: Photosynthesis (60 min)

Target Student Performance

Students use molecular models to explain how carbon, oxygen, and hydrogen atoms in carbon dioxide and water molecules are rearranged into glucose and oxygen in a potato plant’s leaf cells.

Resources You Provide

  • Molecular modeling kit (1 per pair of students; includes 6 carbon atoms, 12 hydrogen atoms, 18 oxygen atoms, 36 or more bond links)
  • Twist ties (12 per pair of students)
  • Scissors (1 per pair of students)

Resources Provided

Recurring Resources


Print one copy of 4.3 Molecular Models for Potato Photosynthesis Worksheet for each student. For each pair of students, print one copy of Molecular Models 11 x 17 Placemat, Forms of Energy Cards, and prepare a pair of scissors. Prepare enough molecular modeling kits for each group. Prepare a computer and a projector to show the PPT while the students are creating models.


1. Use the instructional model to show students where they are in the course of the unit.


Monitor your students’ work as they put together their molecular models. Are they correctly identifying forms of energy on either side of the reaction? Do they understand that all materials used in the reactants must be present in the products? Notice students’ ability to identify molecules that have C-C and C-H bonds as materials that have chemical energy. Use 4.3 Grading Molecular Models for Potato Photosynthesis Worksheet to assess their work. Students should be able to follow instructions and complete the worksheet correctly, so it is reasonable to grade this worksheet.


  • During the demonstration, stress that although we are using twist ties to represent energy, energy actually is not made of matter/molecules!
  • You may want to laminate the Molecular Models 11 x 17 Placemat. These will be used multiple times in each unit.
  • Although we ask students to identify C-C and C-H bonds as high in energy, it is important to recognize that releasing most of that energy requires a reaction with oxygen. It is more accurate to say that the chemical system of glucose and oxygen has more potential energy than the chemical system of carbon dioxide and water.


Students may work in groups of three or four if you are short on molecule kits.

Extending the Learning
  • At the end of the Activity, have students explain the process of photosynthesis to a partner.
  • Have the students “act out” photosynthesis by assigning them molecules using signs. Have them move around the room to represent the process by linking and unlinking hands.
  • Have students compare the chemical reactions for combustion, cellular respiration, and photosynthesis. What do they notice about these reactions?