This five-lesson unit was designed to introduce elementary students to the basic chemistry behind making playdough as they take on the role of a chemical engineer and endeavor to develop a process (or recipe) for making playdough. In addition, it will inject a fundamental knowledge of chemistry, and students will use the basis of this knowledge to improve consistency in producing high-quality playdough that is comparable to retail brand “Play-Doh” in texture, elasticity, and pliability. Along the way, students will learn the role of each ingredient and the reasoning behind each step of the process (mixing, kneading, and applying heat). There will also be room for experimentation as students explore the role of added ingredients and/or vary the preparation and cooking processes. Students will record their measured ingredients and procedures used for each batch of playdough in a chemical engineering journal and present their best final product to the class. The unit promotes an introduction to chemistry, engineering, and using an organized method to record notes and observations. Not only that, but making playdough is a lot of fun! Fair warning – students will be excited, and some results may come out sticky and messy! The unit is designed to take five one-hour long class sessions but can be extended or shortened at the discretion of the teacher.
I personally chose to develop this unit for use in my 2nd grade STEM class and was inspired by an “Engineering is Elementary” unit titled “Improving a Playdough Process.” That unit, however, was largely based on students gathering empirical evidence through collective experimentation and recording of results as they mixed the same amount of flour, water, and salt but in a different order each time. For example, trial one: 2 parts flour, + 1 part salt, mix, add 1 part water, mix again, knead dough. Trial two: 1 part salt and 1 part water, mix, + 2 parts flour, mix, knead, and so on. They would compare their results and decide which set of steps produced the best quality playdough. After several years of teaching that unit, I can attest that neither order of the process consistently produced a high-quality result. The end results often seemed anticlimactic and the students were left with little to no understanding as to why their dough was successful or not. This unit, the Chemistry of Playdough, will greatly expand on the chemistry behind each ingredient and each step of the playdough making process.
The Next Generation Science Standards (referred to as NGSS) in chemistry are non-existent at the elementary level, yet foundational concepts of chemistry come naturally to this kind of unit. However, the NGSS also include eight practices that do connect to this unit. The applicable practices include 1) Asking Questions and Defining Problems, 2) Developing and Using Models, 3) Planning and Carrying Out Investigations, 4) Analyzing and Interpreting Data, 5) Using Mathematics and Computational Thinking, 6) Constructing Explanations and Developing Solutions, 7) Engaging in Argument from Evidence, and 8) Obtaining, Evaluating, and Communicating Information.
This unit was written based on the knowledge I have gained in the Yale New Haven Teachers Institute 2020 Chemistry of Food and Cooking seminar under the guidance of Yale chemistry professor Elsa Yan, as well as my own research, personal experiences and observations as a teacher who has been making playdough with students for years. Much of the background information in the next section is intended to inform and prepare the teacher – to bring you up to par with what I learned as both a teacher and a scholar. I have chosen to structure it in the form of a question and answer section about each ingredient and part of the process. Why do we use flour? Why do we add salt? Water? How do other ingredients, such as cream of tartar, affect the physical attributes of the dough? How does heat play a role in improving the solutions mixed into the compound?
The basic background information, as well as the specific questions, will all be integrated into the lesson plans that are taught to students. Therefore, the subsequent section, How to Teach This Unit, will provide a well-thought out and tested sequence of instructions to help students move beyond the gathering of empirical evidence and lead them to understanding the chemistry behind their observations. As each ingredient is introduced, a scientific explanation will also be included along with relevant demonstrations.
As explained above, my target audience is second grade, seven-year-olds. They have no knowledge of atomic structures, elements, compounds, etc. But they do love to make and play with playdough! This will be a foundational chemistry unit for them well before chemistry is formally taught in school. Yet, the process of making dough that meets certain characteristics is a very natural way to introduce chemistry-related concepts to the very young. Students will make a lot of playdough and record observations as well as rate their final product on a scale we define as a class (high quality, medium quality, low quality). High quality playdough will be stretchy but not sticky. It will be smooth to the touch and pliable enough to mold into a variety of shapes. It will bounce a little bit when dropped (a degree of elasticity) as well as can be stored in a sealed container without growing mold or becoming too hardened. After making basic salt-flour-water dough, students will learn through a mixture of demonstrations and experimentation as they test new ingredients, different types of flour, and different mixing procedures (including adding heat), to answer the question: How can I make high quality playdough that is as good as the store-bought version?