Plants in Your Gas Tank: From Photosynthesis to Ethanol

With ethanol becoming more prevalent in the media and in gas tanks, it is important for students to know from where it comes. This module uses a series of activities to show how energy and mass are converted from one form to another. It focuses on the conversion of light energy into chemical energy via photosynthesis. It then goes on to show how the chemical energy in plant sugars can be fermented to produce ethanol. Finally, the reasons for using ethanol as a fuel are discussed. In the initial activity, students use paper chromatography to separate plant pigments from leaves. In this module’s second activity the students consider what the source of mass for plants is as they grow.  They form hypotheses then design and perform experiments to test their hypotheses. Next the students design an experiment to determine which of three different sugars produces the most fermentation products. Once they figure this out, they then determine what concentration of their "best" sugar would maximize ethanol production and minimize cost. Finally, students discuss the production and use of ethanol as a fuel. This module follows the path of energy from the sun and photosynthesis to ethanol production. Teachers can stress that in every step of the process energy is neither created nor destroyed.  It just changes form.  The same can be said of mass. The module highlights a general method of chemical analysis (chromatography - activity one) that is used in more high tech forms to determine the types and concentrations of fermentable sugars produced from cellulosic biomass. Activity two investigates from where plants get their mass. Producing ethanol from cellulose is difficult but does not compete with food production. Activity three in this module will help show students why it is important to measure the types and concentrations of the sugars produced. PURPOSE OF THE EDUCATION MODULE: The purpose of this module is to help students understand an important aspect of environmental maintenance; the use of plants for the production of fuel resulting in 0-net Carbon Dioxide yield. LEARNING OBJECTIVES: Students will Discuss the role of plant pigments in photosynthesis. Know that photosynthesis produces sugars. Discover that as plants grow the mass required to do so comes from the air(carbon dioxide). Identify ethanol as a product of sugar fermentation and discover that not all sugars produce equal amounts of fermentation products. Relate photosynthesis and fermentation to the concept of conservation of energy and mass. Discuss the environmental and economic benefits of ethanol as a fuel additive. Demonstrate appropriate safe laboratory behavior and techniques. Document observations and data in an organized appropriate laboratory format. Analyze and interpret the results of the experimental data and observations. Communicate their results and conclusions in written lab reports.

Related Topics:
1. Energy is a physical quantity that follows precise natural laws.

Associated Grade Levels:

Related Sub-Topics

1.6 Chemical and nuclear reactions involve transfer and transformation of energy.