Baking quick breads will introduce students to the reaction of base and acid. The use of baking soda will demonstrate how the reaction between a base and an acid will cause the bread to rise without yeast in this chemistry project. This is the fourth part of a series, Teaching through Cooking.
The kitchen offers a wonderful learning experience for all students. Baking quick breads is one way to demonstrate the reaction between a base and an acid. This chemistry lesson plan can be adjusted to suit the ages and specific needs of the students.
Bases and acids or alkaloids and acids react when combined with each other. Many of us are familiar with the reaction of vinegar (an acid) with baking soda (a base). Whether an item is alkaline or acid depends on its pH. Neutral pH is 7, usually tap water is a pH of 7 or close to it. A pH lower than 7 means the item is acidic. A pH above 7 means the item is a base (or alkaline). Baking quick breads is a tasty way to show how the reaction of a base and an acid will cause bread to rise without yeast. This is due to the reaction of milk and baking soda in the recipe.
Students can work in pairs or alone for this part of the project. A pH chart should be available to everyone. Each pair of students should have a small sample of milk, water, and baking soda. Litmus paper should be provided as well. Students should have their science journals ready to write in.
Start by testing the water with litmus paper. Then test the milk. The baking soda will have to be dissolved into the water for best results. Have the students record the results in their science journals.
After explaining what happens when a base and an acid are mixed, ask the students what they think will happen if baking soda is mixed with milk. Their responses should be written in their journals.
In The Kitchen
For this chemistry lesson, choose your favorite quick bread recipe or use one that best suits the equipment and classroom situation. A tasty and healthy quick bread recipe can be found at Recipe Zar
Read over the ingredients with the students. Ask them what they know about yeast. See my article Biology Lesson: Teaching Biology Through Cooking for more information on teaching about yeast. Yeast is missing from the ingredient list. How will the bread rise without yeast? Ask the students to write their hypothesis in their science journals.
Here comes the fun part; prepare the recipe and bake the bread. For this lesson in chemistry ask the students if the bread came out as expected. Did it rise? Why? What other ingredients could be used instead of milk to get a similar outcome? (answer orange juice or similar acidic juices, vinegar is acceptable but not tasty).
Finally, have students write in their journals a summary of what happened in this chemistry project using quick bread.