Introduction

Not many people recognize or even understand the science behind the food they consume.  Food and the way we interact with the food involves a variety of different sciences, including chemistry, biology, physics, microbiology, and engineering but chemistry continuously rises to the forefront.  There is a whole career path dedicated to the chemistry of foods.  Food chemists develop, analyze, and improve foods and beverages.  They make sure that the items we consume follow food laws and labeling requirements.¹⁶ In conjunction with food scientists are flavorists.  Flavorists are able to create and duplicate flavors.  The right flavor can drastically improve the marketability of foods by giving the food a bolder and longer lasting taste to enjoy.  Flavorists are specialized chemists.  They have to understand how chemicals react, how to break down a complicated flavor molecule to recreate it, and how chemicals will behave in the presence of other compounds.¹⁰

We are drawn to foods because of the flavor.  Flavor is not just taste but it is also smell and texture.  Flavor is what defines how we experience food.  It is powerful. It keeps us returning to food.  When we experience flavor, it can stimulate emotions, trigger memories or even warn us of spoiled foods.

Rationale

Through this unit I want my students to understand that all flavors are chemical compounds and that even the way our bodies receive the flavors is a chemical process.  I hope that they see the huge role that chemistry plays in the various foods they eat and how flavor chemists work hard to formulate flavors to keep people returning back to their product.  My students do not realize that there might not actually be strawberry in their strawberry candy.  This is where I want to introduce them to flavor extracts.  Since flavor is a chemical, we can extract that flavor from the plant or replicate that flavor in a lab without actually using the plant.

This unit is meant to be taught at the beginning of the school year.  It will be the gateway to ease the intimidation of their expectations of what chemistry is.  The students will be learning chemistry concepts, as well as teaching strategies that they will encounter throughout the school year.  Most of my activities can easily be altered to apply to a new concept being taught.  Therefore, by introducing these strategies early in the school year, activity transition time can be cut down because the students will already be familiar with the task.

Background

All food has some flavor already present but when we usually talk about flavor we mean the added flavors, which can be either natural or artificial.  Natural flavors are those isolated directly from plants and animals, whereas artificial flavors are synthesized in a lab and made to taste like the natural flavor.  By identifying the exact flavor chemical of a fruit, scientists can reproduce the flavor compound allowing us to enjoy all of the same great smells and tastes of the fruit without the fruit.  This is the big idea behind why candy, soda, chips, and other artificially flavored foods are sold; companies can sell their product cheaper.

The concept of flavor is unique. “Flavor is caused by receptors in the mouth and nose detecting chemicals found within food. These receptors respond by producing signals that are interpreted by the brain as sensations of taste and aroma. Certain taste and aroma combinations are characteristic of particular foods.”⁹

Chemicals in Flavors

The molecules in food are all based on carbon.  Carbon is the second most abundant element in our bodies, accounting for 18% of our body mass.¹² It is essential to all living things making it an important part of our food.  Carbon can be found in all of the carbohydrates, fats, and proteins we eat.

Nitrogen (N), Carbon (C), Hydrogen (H), Oxygen (O), Phosphorus (P), and Sulfur (S) account for 99% of the mass of the human body.¹² (The acronym NCHOPS is a creative way to remember these six elements.)  The way these elements bind together matters in how we taste or smell them.  There are two ways these elements can chemically bond, either by an Ionic bond or a Covalent bond.  Moreover, for these bonds to occur electrons must move around.  Electrons are the negatively charged subatomic particles that oscillate around the nucleus of the atom.  For reference, it should also be noted that there are three subatomic particles: electrons (the aforementioned), protons which have a positive charge and are located in the nucleus, and neutrons which are neutral (no charge) and are also located in the nucleus (Figure 1).

Figure 1. Structure of an atom

In an ionic compound, one element transfers its electrons to another element creating ions (charged elements) that are then attracted to each other (Figure 2).  Ionic compounds form between a metal and nonmetal, and are usually solids at room temperature. Covalent compounds share the electrons between two nonmetal elements (Figure 3).

Figure 2. Ionic bonding model

Figure 3. Covalent bonding model

There are distinct functional groups that are commonly seen on flavor molecules.  For the purpose of my lesson, I have narrowed these down to alcohols, aldehydes, esters, and carboxylic acids. 

Alcohols 

Alcohols are characterized by a hydroxyl group. A hydroxyl group is an oxygen atom (O) covalently bonded  to a hydrogen atom (H).  When naming alcohols, the suffix -ol is used to represent that an OH group is present.

Simple Formula  R-OH 

(“R” represents any length of bonded combinations of carbon and hydrogen atoms)

Simple Structure

(Each point in the structure is a carbon atom)

(Name: Butanol)

Aldehydes

Aldehydes are characterized by a carbonyl group bonded to a hydrogen atom.  A carbonyl group is a carbon atom (C) covalently double bonded to an oxygen atom.  Carbon likes to have 4 bonds so the third bond is with a hydrogen atom and the fourth bond is with the “R” group mentioned earlier.  The carbonyl group is always attached to either the first or last carbon in a carbon chain.  Aldehydes can be identified in a chemical name by the presence of the suffix -al.

Simple Formula  R-CHO

Simple Structure

(Each point in the structure is a carbon atom)

(Name: Butanal)

Esters

Ester are a group of compounds characterized by a central carbon atom double bonded to one oxygen and single bonded to an oxygen group on one side, and a carbon group on the other.  The suffix -oate is used in the naming to indicate a ester.

Simple Formula R-COOR

Simple Structure

(Name: Methyl Butanoate)

Carboxylic Acids

Carboxylic acids are characterized by both a carbonyl group and a hydroxyl group attached to the same carbon.  Like aldehydes, these groups are always bonded to the last carbon in the chain.  Carboxylic acids are named with the suffix -ic acid.

Simple Formula R-COOH

Simple Structure

(Name: Butanoic acid)

Amino Acids

An amino acid is a molecule that contains both a carboxylic acid group and an amine group.  The word amino means that there is an NH₂ (amine) present, usually attached to a carbon.

Example amino acid

(Valine)

Flavor Receptors

Humans have multiple receptors that allow us to sense and experience the world around us.  Of the five traditional senses we all learn (sight, smell, hearing, taste, and touch), taste and smell are the two that we experience chemically.  In order to experience taste and smell, we first need to be able to detect the chemical compounds.  Both taste and smell molecules are detected by either binding to receptors at selective binding sites (G protein coupled receptors) or by allowing the flow of ions across the cell membrane (ligand gated ion channels).¹⁹ Ions dissolved in water are called electrolytes and they create the electrical charge that is able to cross the cell membrane.  GPCRs, on the other hand, work like a lock and key.  As mentioned previously, the shapes of the molecules matter and the receptors can only be unlocked if the right molecule with a fitting shape is inserted, allowing the brain signals to then be transmitted.

There are five basic tastes: sweet, salty, sour, bitter, and umami.  Umami is probably the least known by the general public because it was last to be added as one of our tastes.  Umami is described as a strong savory flavor; think chicken broth, soy sauce and aged cheese. In order for us to experience these taste sensations, the molecules in the food must be soluble (able to dissolve) in water.  Why must it be dissolved in water? Water helps the molecule to gain access to the receptor.  Once the molecule and receptor are linked, a signal is transmitted to the brain.¹⁶

Chemist like to use the expression “Like dissolves like”.  It is meant to describe solubility of a compound.  This means that if the compound is like the liquid you are placing it in then the compound will dissolve.  If it does not dissolve, it is considered to be insoluble.  For example, carbohydrates are made of chains of carbon (C), with OH and H attached to each carbon. (See my example below.) Now think about the structure of water.  Water is H₂O (or HOH).  The OH and H in the carbohydrate give it a similar property of water and therefore carbohydrates dissolve in water.  Fats, on the other hand, are also long chains of carbon but they do not contain any OH groups.  Without the OH, fats do not have the same property of water and they are insoluble in water.

Figure 4. An Example of a Carbohydrate

Chemicals in food are sometimes called tastants and they are detected by the taste buds.  Taste buds are the taste receptors located on the tongue and if viewed closely they look like tiny protrusions on the tongue.  Every person has between 5,000 to 10,000 taste buds.  That is a lot of flavor detection.¹⁸

Developments by John E. Amoore have determined that there are seven primary smells: camphoreous, etheral, floral, minty, musky, pungent, and putrid.²  Examples of each are listed.

• Camphoreous- Eucalyptus, Menthol
• Etheral- Cleaning liquid, Rubbing alcohol
• Floral- Rose, Gardenia
• Minty- Peppermint, Spearmint
• Musky-Animal scents
• Pungent- Smelly cheese, Sardines
• Putrid- Rotten meat

To detect smell, the molecules must be able to move through the air (be in a gaseous state).  This means that those odor molecules must evaporate away from its source and be light enough to float. The smells we detect are called odorants. Once the odorants reach the nose, they fit into the complementary olfactory receptor at the top of the nasal cavity, stimulating them. The shape and size of the odorant molecule determines what receptors they react with, as well as how tightly the molecule binds with the receptor.²  Some molecules bind stronger than others on the receptors. This creates stronger smell sensations. Once detected, a signal is sent to the brain to identify the smell. We (humans) have 450 olfactory receptors. Each receptor is activated by a different odor molecule.  However, one odor molecule can fit several different receptors.  When we smell we are actually receiving signals from a combination of odor molecules all simulating multiple receptors.

Natural vs Artificial Flavor

According to the U.S. Food and Drug Administration’s (FDA) Code of Federal Regulations (Title 21),

“The term natural flavor or natural flavoring means the essential oil, oleoresin, essence or extractive, protein hydrolysate, distillate, or any product of roasting, heating or enzymolysis, which contains the flavoring constituents derived from a spice, fruit or fruit juice, vegetable or vegetable juice, edible yeast, herb, bark, bud, root, leaf or similar plant material, meat, seafood, poultry, eggs, dairy products, or fermentation products thereof, whose significant function in food is flavoring rather than nutritional.”

And the definition of an artificial flavor reads almost the same way. It states, “The term artificial flavor or artificial flavoring means any substance, the function of which is to impart flavor, which is not derived…” from the aforementioned list of materials.³

Through my research it seems that the natural and artificial flavors are not much different.  What makes them different is the way that they are processed.  If all of the starting materials are edible then the flavor extracted is considered natural.  If one or more of the starting materials is inedible then the flavor produced is considered artificial.  However, both produce the exact same flavor molecule and the way that we experience the flavor will be exactly the same.

The esterification reaction is a great example of how two non-plant based compounds can come together to form a flavor.  Esters can also be found naturally in fruits and vegetables.  Each ester has a different scent and the esterification reaction is the result of a scientist isolating the scent compound and recreating it.

Figure 5. Basic Esterification Reaction⁶

In this reaction, a carboxylic acid and an alcohol react together to yield an ester and a water molecule.  This is referred to as a condensation reaction because water is given off as a product.  The products are always the side that the arrow points to.  Also we see in this reaction that in addition to the carboxylic acid and alcohol reactants, there is also an acid being used as a catalyst.  A catalyst is a substance added to a reaction to help speed up the reaction.  Catalysts are not used up or destroyed during the reaction and can be recovered at the end of the reaction.  Acids are substances that willingly donate hydrogen ions (H⁺) to the reaction.  The most common acid used in the esterification reaction is sulfuric acid (H₂SO₄).  Other common examples of acids, though maybe not as useful for this reaction, include: Hydrochloric acid (HCl)-stomach acid, Acetic acid (CH₃COOH)-vinegar, and Ascorbic acid-vitamin C.

There are pros and cons to using both natural and artificial flavors.  Artificial flavors may cost less, provide a more intense flavor, and may be more readily available than the natural derivative.  However, natural flavors have the added health benefit.  When the flavors come directly from the organic source you also receive the nutritional aspects of that source.  Whereas, artificial flavors have little to no nutritional benefit.  Even with this said, the nutritional benefit of a natural flavor is minor and creates no preference over artificial flavoring.

Extractions

Extraction is the process of deliberately drawing out or removing something.  There are various ways to carry out an extraction.  Within a chemistry laboratory, extractions are a way to remove a compound from a mixture by adding an immiscible solvent to the mixture that the desired compound is soluble in but the other compounds in the mixture are insoluble in.  This is done to isolate a pure product by either removing the impurity or by drawing out the pure compound.  When I speak about extracts or extractions in this unit, I am referring to the extractions of chemical compounds from an herb, fruit, or flower by steeping the material in a solvent, which draws the aroma and taste out of the plant body.

The Industrial Revolution brought about the opportunity for foods to be shipped from more distant areas.  However, this created blander food as the foods were preserved and processed for shipping.  To counteract, the need for more flavorful food, the flavor industry was born and it began creating synthetic flavors to replace the lost flavor of industrial processing.

The Germans and the Swiss were the first to significantly expand the artificial flavor market by developing methods to synthesize aromatic compounds.  In the United States, most flavor companies started as importers from Europe.  However, as the food and beverage industries grew, the demand for more commercial flavors also grew and many flavoring companies answered this need by formulating methods to manufacture the flavors domestically.²⁰  Richmond was the first city in the United States to make its mark in this industry.

“In 1884, at age seventeen, Conrad Frederick Sauer began work for a retail and wholesale drug business in Richmond, Virginia... He soon noticed that flavoring extracts formed a large percentage of this business,... Mr. Sauer, a pharmacist by profession but a businessman by preference, saw an opportunity. Why not provide these housewives with pure flavoring extracts, prepackaged, and make them available in grocery stores as well as drugstores?

On October 13, 1887, his twenty-first birthday, C. F. Sauer founded the company that still bears his name at 17th and Broad Streets in Richmond. It was the first company in the country to provide pure flavoring extracts in 5- and 10-gram cartoned bottles, to be sold for 15 and 25 cents, respectively. The company grew rapidly, as Mr. Sauer made products that had once cost a king’s ransom available to homemakers for a few pennies.”¹³

This company stands just a few miles down the road from where a majority of my students live.  It is still in operation today and the Sauer’s Vanilla sign is a cherished landmark.  However, most of my students, have never paid any attention to this building and have no clue what even goes on inside; yet, I am sure that a majority of their parents use or have used many of the C. F. Sauer Company products.

Enhancing Flavors

In our everyday cooking, we inherently do things to enhance the flavor of our foods.  We add butter, we sear our steaks, and we add salt to our dishes.  By doing these things, we bring even more flavor out of our food.  For instance, browning meat by either pan-searing, grilling, or broiling greatly enhances the favor of the meat.  The same goes for vegetables.  A sweetness is brought out in roasted vegetables that you would not otherwise taste without roasting.  Acidic additives like lemon or vinegar give a delightfully balanced dish.  The acids draw out flavors within the foods for us to then eat and enjoy.  Lastly, next to sweetness, salt is probably among the top most used flavor enhancer and the most desired by people.  Not only do we crave saltiness but salt can actually intensify sweetness and reduce bitter flavors.  Common table salt, sodium chloride, is the most well-known and is usually what people think of when the word salt is mentioned.  However, in chemistry salts are the product of acid-base reactions and can describe a wide range of ionic compounds with different levels of saltiness, just like sweeteners give different sensations of sweetness.

One flavor enhancer I want to elaborate more on is browning food.  The browning of food occurs due to the Maillard reaction.  The Maillard reaction is the reaction between an amino acid (protein) and sugar and usually requires heat.  When multiple amino acids are bound together they form proteins.¹ The Maillard reaction occurs when the carbonyl group from the sugar reacts with the amino group in the amino acid.  The results of this are new flavor and odor molecules added to the meat.  Different foods will create different flavors when browned.  This is why grilled vegetables do not taste like grilled meat.

Objectives

My main objective for this unit is to make the connection between biology and chemistry.  Most of my students are coming into the class from Biology and it is easier for them to understand the usefulness of biology, but truly do not understand why chemistry is needed.  The key here is to bridge the gap to show them how the two work together.

At the end of this unit the following objective will have been addressed:

• Connections among sciences
• Demonstration and understanding of safe laboratory practices
• Demonstration and understanding of safe laboratory procedures
• Demonstration and understanding of safe laboratory techniques
• Demonstration of a filtration
• Understanding Material Safety Data Sheet (MSDS) warnings
• Identification of basic lab equipment
• Making measurements and recording data
• Understanding what equipment is needed to measure volume, mass, temperature, and pressure
• Introduction to bonding types: covalent and ionic
• Construction and defense of a scientific viewpoint
• Use of current applications to reinforce chemistry concepts

Strategies and Activities

This unit will be integrated into my chemistry curriculum.  Throughout the school year my students keep a single notebook in which they record all notes and data. Each grouping of notes includes a major heading and a date. Most students keep their notebooks in the classroom but any student is welcome to take it home. (I like to give my students the option to reduce the chance of them losing the notebook.)  For this unit, the students should have headings similar to the headings provided for each lesson.  The thought behind the notebook is that at the end of the year it will become their personal arsenal of information that they can use to study for the  Virginia Chemistry Standards of Learning assessment. Furthermore, each lesson will include an interactive portion to allow the students time to process and practice the information/concept taught to them.  To better scaffold the instruction, I prefer to use a modified version of the I Do, We Do, You (They) Do model.  During the “I Do” portion of the class period, direct instruction is given while the students listen and take notes.  The “We Do” portion is an interactive instruction period for an assignment, where I prompt them with questions, walk around, check work, and give additional information and help.  In the “You Do” portion, students either work independently or collaboratively on an activity with minimal help from me to help me better determine their level of understanding. In using this model approach, you will encounter the following strategies throughout each lesson: effective questioning, collaborative learning groups, progress monitoring, direct instruction with teacher guided note-taking, hands-on learning, debating, nonlinguistic representations, notebooking, and field experience/trip.

Lesson 1: What is flavor?

Warmup: When the students walk through the door, I will give them a piece of fruity candy and a half sheet of paper; then ask them to write a detailed description of the candy.

I Do: After the warmup, I will ask the students what observations they made about the candy.  Students will give their responses and I will explain the difference between observations and inferences.  Then I will ask the students if they have ever thought about how we smell or why our tastes seem to change when we have a cold.  At this point, they should be intrigued and either shouting out possible answers or waiting for the explanation.  This is the time when I will introduce the idea of flavors as chemicals.  Through direct instruction, I will explain how flavors are made of molecules, as well as explain the bonding types and the properties of each.  My students do well with hand drawn visuals so I will also draw out atoms to show how the electrons are moving.

We Do: We will color in individual periodic tables identifying the metals and nonmetals and how to use the periodic table to identify each type of bond within a molecule.  We will watch a video⁴ on ionic and covalent bonding and I will clarify any misunderstandings.  I will then aid students through a collaborative card sort activity (refer to Activity 1) on the properties of ionic and covalent compounds.

You Do: The students will complete a worksheet (refer to Activity 2) individually identifying covalent and ionic compounds while I walk around checking for understanding.

Activity 1: Card Sort (refer to Figure 6): For this activity, I will pre-cut each card, mix them, and place the mixed set in a resealable plastic bag.  My room is set up with 4-person tables. There will be enough sets printed for each table.  The student will separate the cards into two groups; one ionic and the other covalent.  I will circulate around the room giving hints when needed.  Once each table has all of their cards sorted correctly, I will then post the answers and have the students write them as part of their notes for the day.  Each student will make two columns and list each component identifying an ionic compound and each identifying a covalent compound.

Activity 2: Worksheet (refer to Figure 7): The student will complete a worksheet in which they will be able to show their knowledge of ionic and covalent compounds independently.  The first part of the worksheet, they will identify the bonding type of the compounds by identifying whether the two elements being bonded are a metal and non-metal (ionic) or two non-metals (covalent).  The second part of the worksheet asks the student to calculate the difference in electronegativities of the two elements presented and then to determine whether they bond ionically or covalently.  Each student will have a periodic table of electronegativities available.

Takeaway:  I want my students to leave the class thinking about ionic and covalent compounds.  I want them to begin to identify with the chemistry in their lives.  My thought is that they will be at home, glance over at the salt and think to themselves “That’s an ionic compound”.

Figure 6. Card Sort

Enlarge the font and Cut along the dotted lines

Figure 7: Worksheet

Name____________________________________ Date______________  Class Period______

Determine the electronegativity difference and the probable bonding type.

Lesson 2: How our body processes flavor

Warm up:  Students will be given a list of several molecules and asked to identify all of the ionic compounds.

I Do:  I will go over the warm up, then introduce some the key identifying components of molecules.  This is the point when I will discuss NCHOPS (refer the section on Chemicals in Flavor), what the word organic means (in chemistry), and how essential carbon is to human life and our food.  During this portion, students will also follow my lead and take notes on what a functional group is and identify the four main groups I mentioned earlier in the unit. Taste and smell receptors will also be discussed.

We Do:  We will watch a video⁵ on flavor chemistry and discuss functional groups further. I will give each table a structure of a protein, a carbohydrate, and a fat.  They will be assigned to circle all of the functional groups they see in each and identify the name of the group. 

You Do: The students will do a paper domino activity (refer to Activity 3).

Activity 3: Domino activity (refer to Figure 8):  I will have the dominoes already pre-cut, mixed, and put into resealable plastic bags.  The objective is for the student to match the ends of the domino with its corresponding answer. If done correctly, the corresponding answer on the last domino will match the first domino.

Takeaway: This lesson is meant to get them thinking about what they are eating and how their bodies are interacting with the food.   From this lesson, they will see how closely biology relates to chemistry and be able to identify functional groups.

Figure 8: Domino Activity

Enlarge the font and cut along the dotted lines.

Lesson 3: natural versus artificial flavors

Warmup: The students will be asked to define what they think a natural flavor is and what an artificial flavor is on separate sticky notes. I will also have them write their names on the back of the sticky as a quick participation grade. They will then place the sticky notes on the white board underneath the correctly labeled column of either Natural or Artificial.  I will review the posted answers and read all or a few of them depending on how large the class is.  I like to use this strategy in the beginning of the year because my students are not yet as open about sharing information but it is important to me to find out what they already know about a topic.  One way I do this is by having them share information on a sticky note and, instead of having them read it, I read it and share it with the class.  That way no one is singled out and I can still have a mental assessment of what they know.

I Do:  I will show the students the FDA definition of a natural and an artificial flavor.  From this I will have the students help me write our own definition of each.  Then I will explain what a debate is, as well as explain the guidelines of our class debate.

We do/ You do:  Each team will read their articles.  I will give them guiding questions of what to look for in the articles.  Then we have a town hall style debate (Activity 4).

Activity 4: Town Hall Debate:  This activity may expand over two class periods. (1) Separate the class into 4 teams. (2) Determine ahead of time the 4 articles that will be used for the debate.  The two debating sides are the Naturalists (anti-artificial flavors) and the Flavorists (pro-artificial flavors).  Each team will be given different articles to read but two of the articles should lean more against artificial flavoring and two more in flavor of artificial flavoring. (3) Have the students read the article to themselves and then discuss what they read with their team.  During this discussion, they should determine 2-3 main points they determined from the article and then highlight facts and supporting information to back up their claim.  (4) Have each team choose one person to summarize the article to the class.  The person summarizing will mention the main points of the article as well as any supporting information from the article. When that person is speaking there should no interruptions but students are allowed to take notes and write down questions for the opposing side.  (5) After all summaries have been made, all other students now have the opportunity to comment and ask questions by raising their hand.  They are encouraged to provide supporting information from their reading or reputable sites to rebut or support any information mentioned in the summaries.  Extra points will be given to teams who have whole group participation and who show respect for the other teams. (6) At the end of the discussions, allow student time to reflect on the topic by writing their answers to the following questions:  What did you like about participating in the debate? What was the most interesting argument presented? In what ways do you think a class debate helps you in real life situations? Did you ever think about where the flavor came from in your foods before this debate? Has your viewpoint changed about artificial flavors?

Takeaway: I want the students to leave the classroom knowing that they can effectively communicate their viewpoints and ideas without arguing. Also, I hope that this lesson encourages them to think before they speak and to find camaraderie in working as a team.  This lesson will teach them how to construct and defend a scientific viewpoint.

Lesson 4: Flavor extracts and Enhancing flavor

Warmup:  I will give each student two pieces of the candy, preferably the same flavor.  However, one piece will be made with all-natural flavors and the other with artificial flavor but the students will not know.  They are then to vote on whether Candy 1 or Candy 2 was more flavorful.  Then I will reveal to them the difference between the candies.

I Do:  I will go into notes on extracts.  I will discuss what an extract is and what the process of extraction means in chemistry.  I will then discuss flavor extracts and present the students with a question, asking them to give me some examples of flavor extracts they have seen being used in their homes. I will also ask what are some other things that we do to our food to enhance its flavor and discuss ways to enhance flavor. 

We Do/ You Do:  We will make salsa (refer to Activity 5).  We will discuss each ingredient and what flavor it adds to the dish.  I will review the chemistry of some of the ingredients. 

Lesson extension:  To extend the lesson or to add further enrichment for my honors students, I may also discuss esterification reactions to build on how flavors are made.  This added information will give us the opportunity to go over the functional groups found in organic compounds, as well as discuss reversible reactions and use of catalysts.

Activity 5: Making Salsa (a Teacher demo): Part 1-  Ahead of time will have prepared some tomatoes mixed with onions that have been refrigerated overnight.  I will place 2-3 pieces of just the tomatoes in small cups for each student.  I will announce that I mixed the tomatoes with one ingredient, left it overnight and then removed that ingredient. I want the students to try to determine what the missing ingredient is.  My thought for this is that it will help the students get a better understanding of extractions.  The reason they can still smell or taste the onion without it being there is because those flavor chemicals have been extracted from the onion into the juice of the tomatoes.

Part 2- Ahead of time I will precut all ingredients.  I will let the student determine what ingredients might represent each of the 5 basic tastes.  My recommendations are mango-sweet, salt-salty, limes-sour, cilantro and raw onion-bitter, and tomatoes-savory.  I will make a class batch of salsa leaving out the mango and jalapeños for students to add themselves as they please.  The students will then be allowed to eat the salsa while I will give a little background and chemistry about each ingredient.  I will discuss why spicy is not a taste.  Spicy foods contain capsaicin which triggers our pain receptors.  We do not have a spicy taste receptor.  What we call spicy is simply a trick of our minds into thinking we are experiencing heat or a burning sensation. 

Takeaway:  I want my student to leave aware of how everyday things such as making salsa reinforce chemistry concepts.

Lesson 5: Lab Day- Making an Extract

Warmup:  When the students walk into the classroom, hand them an MSDS (Material Safety Data Sheet) of ethanol (the alcohol used in the lab for day) and provide them several questions written on the board. They will have to read through the MSDS to find the answers.  Then as a class discuss the importance of a MSDS and what it tell us about the chemical we are using.

Lab 1:  Make an extract: Students will be divided into groups of 3-4, reminded of the safety procedures, and given a lab sheet to prepare their extract (refer to Figure 9).  The plants I have chosen are ones that have a shorter steeping time.  They are mint, lemon, lime, lavender, orange, and ginger.  I will also purchase a bottle of Sauer’s vanilla extract because vanilla beans take longer to steep than the time available.  (1) Groups who choose mint and lavender will use scissors to cut up the flowers and leaves into small pieces.  For groups who choose a fruit, only the zest is being used and I will provide a zester for those groups. I will also precut the ginger ahead of time. (2) Students should cut or zest enough of the plant or fruit to fill ½ the jar.  Then use weighting paper to weigh the herb in grams and place it into the jar.  (3)  The students are to measure out 50 mL of the alcohol/water solution (vodka) and pour enough into their jar to completely cover the herbs.  Remind the students of the correct way to read a graduated cylinder.  They will have to determine the volume of solution used if the entire 50 mL was not used or if more than the 50 mL was required. (4)  Student need to determine their weight to volume ratio (g/mL). (5) Prepare a water bath and have the students use a thermometer to read and record the temperature of the water. Then have the student place their jars in the warm water for 10 minutes to help reduce the steeping time.  Have them read the temperature again after all the jars have been added.  Talk about the movement of heat.  (6) Remove from the warm water and let the mixture sit for 2-3 days.  Have students shake the jars daily.  (7) When the extracts are done, the student will perform out a filtration.  Using cheese cloth and a funnel, they will filter out the liquid from the solid plant matter into a clean glass jar.

Takeaway:  From this lesson, I want my students to have a better understanding of safe lab practices, procedures, and techniques.  They will leave knowing how to read hazard warning labels and basic lab equipment and their uses.

Figure 9: Extract Lab

Making an Extract

Names of group members: ________________________________________________

Name of the plant or fruit: ____________________ Date of production: _____________

1. Cut (with scissors provided) or zest enough of the plant or fruit to fill ½ the jar. Then use weighing paper to weigh the herb in grams, record your mass in the table, and place it into the jar.
2. Measure out 50 mL of the ethanol/water solution and pour enough into their jar to completely cover the herbs. You do not have to use it and you may add more if needed.  Then record the volume of solution used.
3. Determine their weight to volume ratio and record it in the table.
4. A water bath has been prepared. Twist the lid on tightly and place the jar in the warm water for 10 minutes.
5. Remove the jar from the warm water and let the mixture sit for 2-3 days. Shake the jar daily. 
6. When the extracts are done, we will perform out a filtration using cheese cloth and a funnel to filter out the liquid from the solid into a clean glass jar.

Lesson 6: Lab Day- Making a bath salt scrub

Warmup: This is a great point to talk about the C. F. Sauer company. I will display a photo of the Sauer’s sign and ask the students if have they ever seen the sign and where.  We will discuss the history of the company, its importance to Richmond’s history, and products they own.  Then I will have them check on their extracts and filter them.

Lab 2: Make a bath scrub: After all extracts have finished steeping (2-3 days), explain to students that body scrubs remove dead skin cells from the body through exfoliation and help increase circulation.  By doing this, we are able to absorb moisturizer more easily.  This in turn gives off a fresher more radiant appearance by reducing dark spots from acne and preventing ingrown hair; something all teenagers can relate to.  (1) Have each student determine if they want to make a (white)sugar scrub or an (Epsom)salt scrub, then have them measure or weigh out a predetermined amount and place in their individual plastic container.  (2) Then have the student add half the amount of olive oil to the solid material in the container.  For example, if 2 cups of sugar were used then add one cup of olive oil. (3) Lastly, have the students add 10 drops of one of their extracts or 5 each of two different extracts., stir with a spoon and let them try it out on their hand at the sink. Explain to student not to rub to hard when using their scrub and to not use it all if they have a rash or a skin condition.

Takeaway:  I believe that many of my students will be shocked to learn that Sauer’s was founded in Richmond and is still an important part of Richmond.  Perhaps that could turn into a field trip. Also I want my students to know how to carry out a filtration and when to use filtration as the separation technique of choice.

Lesson 7: Unit Assessment

The assessment will cover identifying functional groups, explaining a filtration, how to respond in an emergency situation based on a MSDS, safe lab practices, instruments to measure temperature, volume, and mass, and identification of bonding types.

Teacher Resources

http://www.ivyroses.com/Chemistry/Organic/FunctionalGroups.php (accessed 7/13)

This site is useful for explaining functional groups and providing examples.

https://blog.mountainroseherbs.com/guide-tinctures-extracts (accessed 7/13)

This website was very useful in explaining how to make extracts at home with fresh herbs, dried herbs, or berries.  The site also provides recommended alcohol percentages based on the type of herb.

https://www.diynatural.com/homemade-body-scrubs/ (accessed 7/27)

This website gave a great description for making a basic body scrub.

https://ed.ted.com/lessons/how-atoms-bond-george-zaidan-and-charles-morton (accessed 7/27)

This video provides another visual on covalent and ionic bonding besides the one referenced.

Salsa Materials: Mango, cilantro, jalapeños, tomatoes, onions, large bowl, serving spoon, small bowls or cups for students, spoons, and tortilla chips

Materials for making an extract: 80 proof vodka, fresh or dried herbs, small mason jars, scales, 50 mL graduated cylinders or larger, cheese cloth, funnel, storage jars, stirrers, and any other equipment you may want to talk about but not necessarily being used.

Material for making the bath scrub: Epsom salt, sugar, olive oil, plastic containers for students to take home.

Student Resources

https://www.youtube.com/watch?v=sn7nvCY0ocY (accessed 7/27)

This site provides a video on reading MSDS labels.

https://www.slideshare.net/CherylBausman/14-laboratory-equipment  (accessed 7/27)

This site provides an overview slide show of basic lab equipment and how they are used.

https://www.texasgateway.org/node/3972 (accessed 7/27)

This site explains how to read a graduated cylinder.

Appendix A: Implementing District Standards

CH.1 The student will investigate and understand that experiments in which variables are measured, analyzed, and evaluated produce observations and verifiable data. Key concepts include

a) designated laboratory techniques;

b) safe use of chemicals and equipment;

c) proper response to emergency situations;

e) accurate recording, organization, and analysis of data through repeated trials;

i) construction and defense of a scientific viewpoint; and

j) the use of current applications to reinforce chemistry concepts.

CH.2 The student will investigate and understand that the placement of elements on the periodic table is a function of their atomic structure. The periodic table is a tool used for the investigations of

a) average atomic mass, mass number, and atomic number; and

c) mass and charge characteristics of subatomic particles;

CH.3 The student will investigate and understand how conservation of energy and matter is expressed in chemical formulas and balanced equations. Key concepts include

d) bonding types

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