3.2.7a - Explain and apply scientific and technological knowledge
3.2.7b - Apply process knowledge to make and interpret observations
3.2.10b - Describe and explain the chemical and structural basis of living
3.4.7a - Describe concepts about the structure and properties of matter
3.4.10a - Explain concepts about the structure and properties of matter
3.6.7a - Explain biotechnologies that relate to related technologies of propagating, growing, maintaining, adapting, treating, and converting
Students will know that
- There are reasons why our society needs to consider the use and implementation of alternative fuels.
- When yeast cells ferment simple sugars (such as glucose), ethanol and carbon dioxide are produced.
- Ethanol is a renewable fuel and is considered to be “CO 2 neutral.”
- Using ethanol as a fuel is not a new development in our society; it has been used since the late 1800’s on and off throughout history as certain situations have dictated.
Students will be able to
- Provide evidence that a chemical reaction is occurring.
- Conclude that the inflation of a balloon is evidence that ethanol is being produced.
- Draw diagrams that show how ethanol is considered to be “CO 2 neutral” and why fossil fuels are not.
- Make and test predictions about whether or not certain substances are fermentable by yeast.
- Evaluation of completed student handout.
- Class discussion of key ideas throughout the activity.
Part 1 (Hmwk Assignment & 25-min class discussion)
- Have the students complete the readings and questions in Part 1 as a homework assignment. If desired, go over the answers as a class.
- Solicit student thoughts about why we need to consider using alternative fuels. During this class discussion, emphasize that fossil fuels are a finite resource, that it is not ideal to depend so heavily on foreign countries for such a large portion of our fuel, and that burning fossil fuels produces harmful emissions.
- Introduce ethanol as one type of alternative fuel. Tell the students this is the alternative fuel they will be investigating during this lesson.
Part 2 (1, 45-min class period)
- Distribute the materials for the preliminary investigation with sugar and yeast. In this investigation, students will combine dissolved glucose tablets with yeast in a soda bottle and watch what happens to a deflated balloon placed over the mouth of the bottle. Have the students follow the directions in their handout for this investigation.
- While students are observing the balloon over the course of 30-40 minutes, have them complete the reading on fermentation in their handout.
- Have the students answer the questions in their handout to help them make sense of what they observed with their balloon. Students are asked to provide evidence of the chemical reaction and fermentation that occurred, and they decide whether or not ethanol was produced. These questions also guide the student in concluding that glucose is a simple sugar.
Part 3 (1, 45-min class period)
- Write the five substances the class will test for ethanol production on the board: corn syrup, corn starch, table sugar, apples, and honey.
- Have students think about what they expect to see by answering the questions in their handout. Refer them to the table in the Additional Resources section of their handout to help them make predictions about which substances yeast will be able to use to produce ethanol.
- Divide the students up into five groups, and assign each group one of the substances to test. Have them rinse out and re-use their soda bottles from Part 2. For the students testing apples, give them about ¼ of an apple, sliced into small, thin pieces.
- After students have tested their assigned substances, have them share their observations with the rest of the class. Have the students record one another’s findings in the table provided in their handout.
- Point out to students that complex sugars can still be used in ethanol production, as long as they are broken down by enzymes first. At the conclusion of this part, point out that corn syrup was once corn starch. The same enzymes used in human digestion were added to the starch, and the starch became a syrupy liquid of simple sugars (corn syrup).
Part 4 (30 min)
- Have the students reach their own conclusion about the production of CO 2 produced during the production of ethanol by answering questions in their handout.
- Explain why ethanol is considered to be “CO 2 neutral” (refer to Teacher Notes for this explanation). Use the overheads provided.
- Have the students make sense of this by completing the illustrations in their handout.
Part 5 (Hmwk Assignment)
- Assign the questions in Part 5 for homework. If desired, go over the answers.
- Be sure that the students have made the connection between the substances they tested and the actual crops they came from (corn, sugar cane, etc.), as this should help them understand why ethanol is a renewable resource. Also emphasize that fossil fuels are considered nonrenewable because they take millions of years to replace.
Part 6 (Variable)
- Have the students complete the questions in Part 6 as an in-class or homework assignment. Make sure students understand that ethanol has been used as a fuel for many years, and is not merely a passing fad.