University of Michigan



Chemical Engineering: Toothpaste DesignTarget AudienceThe toothpaste activity could be adapted to be suitable for different age groups and highlights engineering design principles. This document provides an outline of the activity for the corresponding age group. Middle SchoolThis activity puts the students in the role of a chemical engineer it may be useful to first introduce engineering and the different types of engineersEngineers use science and math to solve problems in the real worldChemical engineers specifically use chemistry, physics, math, and biology to attack different challenges through different rolesIntroduce production engineering of consumer products such as toothpasteEmphasize that engineers have roles in product development Give the students the goal of an engineer is to design processes that produce high quality products in large quantities and at low costsIntroduce the goal of the project: Make toothpaste that satisfies the following criteriaSatisfy consumer demandMinimize research and development costsAdhere to material/process constraintsGo over each of the materials present Engineering Constraints and useful conversions with the class as a wholeMaterial and Processing CostsIngredientPurposeRaw Material CostUnitBaking SodaCleaning0.30$/tspGlycerinTexture0.30$/tspCorn StarchTexture0.05$/tspOrganic Corn StarchTexture0.10$/tspPeroxideWhitening0.80$/mLFluoridePrevents cavities0.60$/mLSaltFlavor0.05$/tspDyesColor0.05$/dropOrganic DyesColor0.10$/dropExtractsFlavor0.50$/mLOrganic ExtractsFlavor0.75$/mLEngineering Constraints Test batch size should be ~1-2 ounces1 drop of dye is plenty to color 1-2 ounces of fluid To prevent paste from being too runny ~3/4 of the volume should be solids Greater than 90% solids will cause blockage in the processing equipmentFor simplicity, assume 1mL of fluoride or peroxide corresponds to 1% total contentPaste must contain at least 10% Baking Soda to effectively clean teethAbout 1 mL flavoring per ounce will give a strong, but not overpowering taste Peroxide is only effective for whitening at concentrations >2%, but can burn skin at > 5%Fluoride concentration must be greater than 0.5% to be effective Useful Conversions6 tsp = 1oz5mL = 1tsp~10 drop = 1mLSplit the students up into groups of 3 or 4 with each group being assigned a different consumer persona (attached)The groups should first be given time to read the consumer demands and come up with an idea for a first formulation using the given worksheetMS-ETS1-1 Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.Followed by the students actually making the toothpaste with the available supplies---encourage the students to try their toothpaste/would you use this?Have each student calculate the cost of their formulations while asking the question could this be made cheaper and still satisfy the consumer demandsGive the students time to calculate research cost and fine tune their formulations to get the cheapest toothpaste that satisfies demands and they would actually use(would encourage students to try at least 3 different formulations and calculate cost on the worksheet)MS-ETS1-2 Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem. MS-ETS1-3 Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.Sample debriefing questionsDid you come up with a recipe that worked? If not, what was the issue? How could you address this in the future?How did you tailor your toothpaste formulation to your client’s specific needs? How much did your toothpaste cost? What was the major contributing factor to the cost? How could you make a cheaper toothpaste?High School This activity puts the students in the role of a chemical engineer it may be useful to first introduce engineering and the different types of engineersEngineers use science and math to solve problems in the real worldChemical engineers specifically use chemistry, physics, math, and biology to attack different challenges through different rolesIntroduce production engineering of consumer products such as toothpasteEmphasize that engineers have roles in product development and mass productionGive the students the goal of an engineer is to design processes that produce high quality products in large quantities and at low costsIntroduce the goal of the project: Make toothpaste that satisfies the following criteriaSatisfy consumer demandMinimize research and development/production costsAdhere to material/process constraintsMinimize health and environmental impactGo over each of the materials’ present Engineering Constraints and useful conversions with the class as a wholeMaterial and Processing CostsIngredientPurposeRaw Material CostProcessing CostUnitBaking SodaCleaning0.300.10$/tspGlycerinTexture0.300.05$/tspCorn StarchTexture0.050.10$/tspOrganic Corn StarchTexture0.100.10$/tspPeroxideWhitening0.801.00$/mLFluoridePrevents cavities0.600.50$/mLSaltFlavor0.050.10$/tspDyesColor0.050.01$/dropOrganic DyesColor0.100.02$/dropExtractsFlavor0.500.05$/mLOrganic ExtractsFlavor0.750.07$/mL*Pure peroxide is corrosive, requiring expensive resistant materials in processingEngineering Constraints Test batch size should be ~1-2 ounces1 drop of dye is plenty to color 1-2 ounces of fluid To prevent paste from being too runny ~3/4 of the volume should be solids Greater than 90% solids will cause blockage in the processing equipmentFor simplicity, assume 1mL of fluoride or peroxide corresponds to 1% total contentPaste must contain at least 10% Baking Soda to effectively clean teethAbout 1 mL flavoring per ounce will give a strong, but not overpowering taste Hydrogen Peroxide only effective for whitening at concentrations >2%, but can burn skin at > 5%Fluoride concentration must be greater than 0.5% to be effective Useful Conversions6 tsp = 1oz5mL = 1tsp~10 drop = 1mLoz in a regular tube of toothpaste Split the students up into groups of 3 or 4 with each group being assigned a different consumer persona (attached)The groups should first be given time to read the consumer demands and come up with an idea for a first formulationFollowed by the students actually making the toothpaste with the available supplies---encourage the students to try their toothpaste/would you use this?Have each student calculate the cost of their formulations while asking the question could this be made cheaper and still satisfy the consumer demandsHS-ETS1-3 Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, and aesthetics, as well as possible social, cultural, and environmental impacts. Give the students time to calculate research cost and fine tune their formulations to get the cheapest toothpaste that satisfies demands and they would actually use would encourage students to try at least 3 different formulations and calculate research and production cost for the formulation on the worksheet)Once the final formulation is determined use that formulation and the production cost to scale up the recipe to make a large tube of toothpasteHS-ETS1-2 Design a solution to a complex real-world problem by breaking it down into smaller, more manageable problems that can be solved through engineering.Sample debriefing questionsDid you come up with a recipe that worked? If not, what was the issue? How could you address this in the future?How did you tailor your toothpaste formulation to your client’s specific needs? How much did your toothpaste cost? What was the major contributing factor to the cost? How could you make a cheaper toothpaste? ................
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