In this activity, students will be given a common homemade recipe for German chocolate cake with measurements in English units. They will be asked to convert the English ingredients list to metric units through scientific calculations. Students will also be asked to identify the ingredients as solid, liquid or gas. While reviewing the cooking procedures, students will classify certain steps as containing compounds or mixtures as well as identify whether chemical or physical changes are taking place. The culinary chemistry involved in this lesson should be introduced throughout the activity.
Middle or High School
This activity will help prepare your students to meet the performance expectations in the following standards:
- MS-PS1-2: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.
- 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.
- Scientific and Engineering Practices:
- Using Mathematics and Computational Thinking
By the end of this activity, students will be able to:
- Perform English to metric unit conversions.
- Identify the three states of matter.
- Distinguish between chemical and physical changes.
- Distinguish between compounds and mixtures.
This activity supports students’ understanding of
- Dimensional Analysis
- Chemical Change
- Physical Change
Teacher Preparation: 10 minutes
Lesson: 45 minutes
- Student worksheet
- Metric to English conversion table (available to download)
- There are no safety concerns associated with this activity.
- For advanced students, you could also include metric to English conversions.
- Some conversions can be done with one step; others can be done with two or more steps. You can decide which to use with the conversion information in the student activity and the conversion chart that is provided with this lesson.
- This German chocolate cake recipe was used for this lesson.
- An answer key has been provided for teacher reference.
For the Student
Today you will be given a recipe to make a delicious German chocolate cake. In this activity you will apply three key concepts from classroom learning. Using your calculator, you will perform English to metric conversions. You will visualize in your mind the process of making a cake and identify the chemical and physical changes that occur. Finally, you will distinguish between a compound and a mixture during the process.
- Give an example of an element and an example of a compound.
- Explain why a cake is a homogeneous or heterogeneous mixture.
- While making a cake, how can you identify whether each step is a chemical or physical change?
- Practice English to metric conversions.
- Identify three states of matter.
- Classify ingredients as compounds or mixtures.
- Distinguish between chemical change and physical change.
- Student worksheet
- Pencil / Pen
- Metric to English conversion table
- The following recipe was used for this lesson: http://bit.ly/cake-conversion
- Complete the table below:
- Next to each ingredient in the “State” column cell write “S” if it is a solid, “L” if it is a liquid, and “G” if it is a gas.
- Next to each ingredient in the “Mixture or Compound” column cell write a “C” if it is a compound or “M” if it is a mixture.
- For each ingredient that is identified as a compound write its chemical formula in the “Formula” cell. You may need to look it up.
- For each ingredient that is identified as a mixture indicate whether it is heterogeneous or homogeneous in the last column of the table.
- Complete the metric to English calculations and conclusions sections. The required conversions are included in the conversion table and at the end of these instructions
|Ingredient||State (S-L-G)||Mixture or Compound||Formula (if compound)||Heterogeneous or homogenous (if mixture)|
|For the Chocolate Cake|
|2.00 cups sugar|
|1.75 cups flour|
|0.75 cups cocoa powder|
|1 1/2 teaspoons baking powder|
|1 1/2 teaspoons baking soda|
|1 teaspoon salt|
|2 large eggs|
|1.0 cups buttermilk|
|0.50 cups vegetable oil|
|2 teaspoons vanilla extract|
|1.00 cups boiling water|
|For the Chocolate Frosting|
|0.500 cups butter|
|.667 cups cocoa powder|
|3.00 cups powdered sugar|
|0.333 cups evaporated milk|
|1 teaspoon vanilla extract|
|Useful Food Conversions|
|White Sugar||1 cup = 200.0 grams|
|White Flour||1 cup = 125.0 grams|
|Cocoa Powder||1 cup = 120.0 grams|
|Butter||1 cup = 228.0 grams|
|Powdered Sugar||1 cup = 125.0 grams|
|All Food||1 cup = 16 tablespoons|
|All Food||1 tablespoon = 3 teaspoons|
Convert the following ingredient units using your conversion table. Note that the temperature and pan size were not ingredients but must still be converted. For full credit please show your work with proper dimensional analysis and number significant figures.
|2.00 cups sugar to grams|
|1.75 cups flour to grams|
|0.75 cups cocoa powder to grams|
|8.00 tablespoons butter to grams|
|0.667 cups cocoa powder to teaspoons|
|3.0 cups powdered sugar to grams|
|1.00 cups buttermilk to mL|
|0.50 cups vegetable oil to mL|
|0.333 cups evaporated milk to mL|
|1.00 cups boiling water to L|
|375°F to °C|
|8.0 or 9.00 inches to cm|
- Why didn’t you need to convert the baking time from the metric recipe?
- Find and explain two steps in the recipe that involve physical changes. Explain how you know they are physical changes.
- Find and explain two steps in the recipe that involve chemical changes. Explain how you know they are chemical changes.
- Baking involves many chemical changes. One of those changes allows the cake to rise. The main mechanism for this is the release of carbon dioxide. Which compound(s) from the ingredients list do you think releases this carbon dioxide? How do you know?
- The recipe instructs you to cook for 25-35 minutes. One of the reasons cook time might vary is the size of the pan you select. Which size pan would take less time to cook and why?
- Another variable that can affect bake time is what the pan is made of. What differences will there be if you bake you cake in a glass pan vs. an aluminum pan? (You can research this topic)
- When opening the oven to remove your cake, why would it be smart to close your eyes and hold your breath for the first few seconds?
- The recipe notes that if baking at high altitude add 3 tablespoons extra flour. Why would you add more flour if cooking at higher altitudes?
- Write a brief summary of what you learned in this lab that includes how the objective was met.