Ag & Energy - Lesson 12 - Chemical Reactions

Ag & Energy - Lesson 12 - Chemical Reactions

Target Grade Level / Age Range:

High School: 9-12


90 Minutes


As a result of this lesson, the student will …

  1. Define and identify the fermentation process.
  2. Recognize the reactions that occur in the fermentation process.


  • Writing surface
  • Tape/other means to affix paper to writing surface
  • Scissors
  • Safety glasses
  • Variety of fermented foods (cheese, cider, bread, yogurt, salami, soy sauce, and sauerkraut)
  • 8 oz. water/pop bottle
  • 1 balloon
  • 8 or more packages of yeast
  • Ice
  • Measuring spoons
  • Flour
  • Salt
  • Sugar
  • Vinegar
  • Stirrers
  • Heating element
  • 4 clear glasses

Suggested Companion Resources


  • Ethanol
  • Fermentation- Any of a group of chemical reactions induced by microorganisms or enzymes that split complex organic compounds into relatively simple substances, especially the anaerobic conversion of sugar to carbon dioxide and alcohol by yeast.

Background – Agricultural Connections

When conducting the experiments, the instructor should understand what the students are seeing and be able to explain it if the students have questions. If reactions occur in the containers, they are evidenced by bubbles beginning to form and burst (yeast producing carbon dioxide). The mixture will likely start to expand a little as carbon dioxide is formed. The container will changes smells – initially a very yeasty smell to later a slightly alcohol smell. The container may warm slightly (the chemical reaction is slightly exothermic and should produce a little heat). The temperature of each container could also be measured as another component of the experiment.

In the first phase of the experiment, the yeast should be able to eat the flour. The salt should inhibit the activity of the yeast because it has changed the pH of the solution (basic). The sugar should speed up the reaction with readily available food for the yeast to eat. The vinegar should inhibit the yeast because again you have changed the pH of the solution (acidic).

In the second phase of the experiment, the boiling water should inhibit the yeast. Yeast is a living organism that cannot survive in boiling water. The boiling water should actually kill the yeast. The warm water should be an ideal environment for the yeast and this beaker should produce the best results. The cold water should inhibit the yeast and minimize growth. The yeast will be very slow to activate. The ice water should kill or severely inhibit the yeast growth. Again, yeast is a living organism that cannot survive in freezing temperatures.

Interest Approach or Motivator

Have students begin thinking about the term fermentation and the changes that take place in the fermentation process. Use a variety of examples of food that are fermented: bring in examples, show pictures, or talk about the examples. Examples include: cheese, cider, bread, yogurt, salami, soy sauce and sauerkraut. Have students write down their thoughts or elicit ideas in a class discussion. In addition, the instructor may have the students taste each food and consider how it benefitted from the fermentation process (i.e.: cheese, flavor and preservation; sauerkraut, flavor, etc.)

One of the similarities between these types of foods is that they went through a fermentation process to get to the final product. The reason the fermentation process is used is to help preserve certain foods, and provide aromas and flavors in others. Fermentation is used for a different reason in non-food sources like fuel, and that is what we are going to discover today. Even though we ferment different substances for different reasons, the process is basically the same. Today we will take a look at that process particularly in relation to the production of ethanol.

Approximately 15 minutes prior to class, combine ½ cup of lukewarm water, one packet of yeast, and 5 Tbsp of sugar into a 1 liter pop bottle. Place a balloon over the top pop bottle. By the time students arrive the yeast should have begun to eat the sugar and convert it to ethanol. The carbon dioxide byproduct will be released and begin to fill up the balloon. Use this as another example of fermentation and ask students to think about what is happening. Why is the balloon expanding?


OBJECTIVE 1. Define and identify the fermentation process.

Prior to class, write each word in the definition of fermentation on a separate note card.

Fermentation is a sequence of reactions which release energy from organic molecules in the absence of oxygen.

Provide the notecards to the class and instruct them to work together to order the words to create the definition. If in a large class, break into smaller groups and provide a set of cards to each group. Guide the students through the process of assembling the cards into a definition. Have them spread the cards out along the tables/desks.

Allow 5-8 minutes for students to order the terms. The instructor can help students by pulling words out that are not in order or by asking students questions to consider whether the word is in the best place. Once they have ordered the words correctly have them affix the words in order to the writing surface and record the definition in their notes.

  1. Ethanol is a product of fermentation. Fermentation is a sequence of reactions which release energy from organic molecules in the absence of oxygen.
    1. In this application of fermentation, energy is obtained when sugar is changed to ethanol and carbon dioxide.

The end goal in the process of fermentation in this case is energy. This energy is obtained when sugar is changed to ethanol and carbon dioxide. We can represent this process by using an equation. Energy can be represented by E on the right side of the equation

= E

Sugar is the input to the equation, or the first ingredient? Sugar can come from a number of types of plants, including corn. In the equation, use S to represent sugars. This will go on the far left of the equation.

S = E

Energy is produced when sugar is changed to ethanol and carbon dioxide, so the sugar goes through a transformation. Since we are working in mathematical terms with our equation, you could say the sugar is divided by two into ethanol and carbon dioxide. Let’s show how this might look in our equation:

S / 2 →  Eth + CO2 = E

Notice in our equation we used an arrow to represent what happens after sugar ferments. This arrow means “yields.” To rephrase the statement above, the process of fermenting sugar yields ethanol and carbon dioxide, which equals energy. This equation can come in handy as a quick reference when thinking about what happens in the fermentation process.

OBJECTIVE 2. Recognize the reactions that occur in the fermentation process.
  1. Yeast feeds on the sugars and releases carbon dioxide.
  2. Bubbling or the release of carbon dioxide should be present.

Pass out the student experimentation worksheet. Have students read through all of the instructions to the experiments. Break students into work groups. Read through the list of materials and ask students to locate the materials where they have been set out. Briefly talk through each step of the experiment to ensure students understand the steps. Allow students begin to conduct experiment A. The instructor should make determinations as to whether the experiments should be conducted separately or simultaneously depending on time.

Experiment Note: If time does not allow the proper sequence of lab steps, you will have to simultaneously run Experiment A and B at the same time or spend two different days completing the lab.

The instructor should circulate through the room to assist students in conducting the experiment and answering questions. After students have completed the experiment, talk through responses with the class to come to a consensus on the outcome. Discuss what the results in beaker 1. Beaker 2, 3, and 4.

Once experiment A is complete, have students read through and then talk through experiment B with students to ensure they understand the steps. Continue with experiment B. After the students have conducted experiment B, talk through student responses, similar to experiment A. These discussions will vary based on student responses. The instructor should guide students through the discussion to logical conclusions.


Have students explain the observations and concepts learned during the fermentation lab associated with each objective. Student’s responses can then be used to determine which objectives need to be further explained and which objectives are fully understood.

Review the experiments with the students by having them record one important point they learned from each experiment. Allow about 2 minutes for students to reflect, adjust depending on student pacing. Have students share these important points in groups of 2-3. Then have students get back into small groups to share important points. Finally, pass out the evaluation for students to complete.

Answers to Evaluation:

Fill in the Blank:

  1. Fermentation
  2. Carbon dioxide
  3. Sugar

Short Answer:

  1. The warmer the temperature the more likely fermentation will occur. However, in extreme temperatures of hot and cold such as freezing and boiling, yeast will become inactive or die off.

Essential Files (maps, charts, pictures, or documents)

Did you know? (Ag facts)

  • The ideal temperature for yeast multiplication is between 20 degrees Celsius (68F) and 27 degrees Celsius (81F).
  • The ideal range for fermentation is between 27 degrees Celsius (81F) and 38 degrees Celsius (100F).

Extension Activities

  • Instructors can lead students in making cheese or bread in the classroom, focusing on the fermentation process and comparing the process to the content learned in the current lesson.
  • Have students plan and conduct their own agriscience experiment on the fermentation process.


  • Adapted from Renewable Fuels Instructional Materials: Copyright © 2009 by National FFA Organization. Used by permission.
  • E-Moments® is a registered trademark of the National FFA Organization. Copyright © 2004 by National FFA Organization. Used by permission.
  • New materials, updates and revisions were funded in part by a grant from the Iowa Energy Center as a special project of the Iowa Agriculture Literacy Foundation.


Will Fett

Organization Affiliation

Iowa Agriculture Literacy Foundation

Agriculture Literacy Outcomes

  • Theme 4: STEM
    • Provide examples of how processing adds value to agricultural goods and fosters economic growth both locally and globally

Education Content Standards

  • HS-PS1-2. Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.
  • HS-PS1-4. Develop a model to illustrate that the release or absorption of energy from a chemical reaction system depends upon the changes in total bond energy.
  • HS-PS1-5. Apply scientific principles and evidence to provide an explanation about the effects of changing the temperature or concentration of the reacting particles on the rate at which a reaction occurs.

Common Core Connections

  • NL-ENG.K-12.8. Developing Research Skills.
  • SL.9–10.1  Initiate and participate effectively in a range of collaborative discussions (one–on–one, in groups, and teacher–led) with diverse partners on grades 9–10 topics, texts, and issues, building on others' ideas and expressing their own clearly and persuasively