Objectives
Students will understand the following:
That naturally occurring fats and oils are mixtures.
The relationship between carbon-carbon chemical bonds and states of matter.
The relationship between chemical bond strength, thermal oxidation, and how they relate to saturated, monounsaturated, and polyunsaturated fats.
Procedures
In discussion, assess your student’s understanding of the chemistry of naturally occurring fats and oils. Determine whether they understand that fats and oils are complex mixtures that share common chemical features, differing primarily in the occurrence of double bonds. Determine if they understand that carbon-carbon double bonds are weaker than carbon-carbon single bonds.
If students need background information on fats and oils, assign research into the chemical differences between saturated oils, monounsaturated oils, and polyunsaturated oils. Their research should give them some understanding of why an oil is classified as saturated, monounsaturated, or polyunsaturated.
Hold a post-research discussion on the student’s findings. Question students on why saturated oils are more likely to be solids at room temperature, while unsaturated oils tend to be liquids at room temperature. Encourage them to think about why saturated oils are less likely to go rancid than unsaturated oils. Why would companies prefer to use saturated oils in their products?
Conduct the following demonstration:
Weigh a 5-gram sample of each oil into separate beakers.
In a well-ventilated area (preferably a hood, or outdoors) use the butane grill lighter, ignite each oil.
Ask the students to record their observations. Specifically, what colors do they observe when each oil burns? How much smoke do they emit, and what are its characteristics?
Using their observations, can they predict how stable each oil would be when stored at room temperature? For deep frying? For baking?
Using their observations as a basis for discussion, ask students to canvas community restaurants to learn which fats and/or oils local businesses use most often. What is preferred for frying applications vs baked goods? Do businesses have a rationale for their choice? How does that compare against the health benefits of each oil?
Ask students to write a paragraph explaining how the presence, and extent of unsaturation in an oil helps determine whether it is a solid or liquid at room temperature. Based on their observations, can they predict which of the oils may be the healthiest, and why? Do their observations provide any insight into the storage stability of each oil? Students should attempt to link the observations from the demonstration with their research and class discussion. Have them share their paragraph and discuss the results.
Adaptations
Have students try comparing the influence of different cooking oils on a variety of baked goods. Assign students the task of baking a variety of items using oils rich in saturated vs. monounsaturated vs. polyunsaturated oils.
Discussion Questions
What motivated corporations to develop partially hydrogenated oils in commercial foods? Can the properties unique to partially hydrogenated oils be obtained from naturally occurring oils?
Do trans fats exist in nature? How to they appear in foods, and what makes them objectionable?
What naturally occurring oils are solids at room temperature and why? How does the number of double bonds in a given fatty acid influence its state of matter? Are the times when a chef would need to use a oil that is a solid at room temperature?
What are essential fatty acids, and which of those must humans obtain from other sources? Are they used extensively in foods? Why or why not?
Is cholesterol found in all oils? What is the plant equivalent of cholesterol, and how does that influence human health?
Evaluation
You can evaluate your students on their paragraphs using the following three-point rubric:
Three points: distinctly expresses writer’s opinion about the benefits and/or detriments of oils and fats on human health, and how chemical bonding influences those benefits; backs up opinion by clearly citing abundant information learned in research and observation; at least three sources quoted; no errors in grammar, usage, and mechanics.
Two points: adequately expresses writer’s opinion; backs up opinion by citing some information learned in research; few observations from demonstration quoted; some errors in grammar, usage, and mechanics.
One point: No clearly expressed opinion; opinion backed up by little information learned in research; no observation from demonstration quoted; many errors in grammar, usage, and mechanics.
You can ask your students to contribute to the assessment rubric by determining how much information should be considered adequate to back up an opinion, and how observations from the demonstration should influence their opinion.
Extensions
Energy Policy & Biofuels
The push for increased use of biofuels, and biodiesel in particular, has a dramatic impact on the cost and availability of oils for human consumption. Working in groups, have students make policy decisions about the use of biodiesel. Ask students to keep the following in mind when making their decisions:
What properties about an oil make it desirable for the manufacturing of biodiesel?
Chemically speaking, what is the best naturally occurring source of oil for making biodiesel, and why?
Is the best oil the most cost effective oil?
How does the use of land for making biodiesel influence human food production? What are the global effects (if any) of those choices?
What is the environmental impact of biodiesel production? In particular, consider the influence of increased fertilizer use. How does one weigh the environmental cost of fertilizer pollution against the possible environmental benefits of biodiesel use?
Why is biodiesel production so costly, when compared against traditional diesel production from an oil refinery?
When they’re done, ask groups to compare their decisions with the rest of the class. Have a discussion about the costs and benefits of biodiesel. Does pursuing widespread biodiesel production benefit mankind?
Suggested Reading
Links
Learning About Alternative Energy — Biofuels
Find information about biofuels, their composition, and their growing influence on U.S. energy policy.
Chemistry Of Trans Fats
Learn about the science of trans fats and their impact on human health.
Chemistry of Dietary Fat
Great information about the science of fats.
Cooking Oils
Find information about different how the chemistry of cooking oils can influence human health.
Canola Oil
Covers the development of canola and how its composition compares against its parent plant, the rapeseed plant. Provides insight into its use in cooking, and influence on human health.
Fatty Acid Chemistry
Intro to fatty acid chemistry.
Peanut Oil
Provides information about how peanut oil is harvested and its chemical composition. Explains why it is desirable for use in high temperature applications, and how that translates to an impact on health.
This lesson plan may be used to address the academic standards listed below. These standards are drawn from Content Knowledge: A Compendium of Standards and Benchmarks for K-12 Education: 2nd Edition and have been provided courtesy of the Mid-continent Research for Education and Learning in Aurora, Colorado.
Standards
Grade level:6-8
Subject area:Science
Standard:
Understands the interactions of science, technology and society.
Benchmarks:
Knows that science helps drive technology, as it provides knowledge for better understanding, instruments and techniques.
Grade level:6-8
Subject area:Science
Standard:
Understands the interactions of science, technology and society.
Benchmarks:
Knows that technology is essential to science because it enables observations of phenomena that are far beyond the capabilities of scientists due to factors such as distance, location, size and speed.
Grade level:9-12
Subject area:Science
Standard:
Understands the interactions of science, technology and society.
Benchmarks:
Knows that science often advances with the introduction of new technologies and solving technological problems often results in new scientific knowledge; new technologies often extend the current levels of scientific understanding and introduce new arenas of research.
Grade Level: 6-8
Subject Area: Health
Standard: Knows how to maintain and promote personal health.
Benchmarks:
Knows strategies and skills that are used to attain personal health goals.
Grade Level: 9-12
Subject Area: Health
Standard: Knows how to maintain and promote personal health.
Benchmarks:
Knows how personal behaviors relate to health and well-being and how these behaviors can be modified if necessary to promote achievement of health goals throughout life.
Grade Level: 9-12
Subject Area: Health
Standard: Knows health risk factors and techniques to manage and reduce those risks..
Benchmarks:
Knows how make positive health decisions related to injury, tobacco, nutrition, physical activity sexuality, and alcohol and other drugs.
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