Taking the Biscuit

Beverly Coulter explains how she introduces process engineering concepts to new undergrads via the Chocolate Chip Cookie Challenge

IT IS the end of February 2021 and the start of another academic year at the University of Queensland (UQ) Brisbane, Australia. Here in the School of Chemical Engineering at UQ we are looking forward to welcoming 130 bright-eyed Year 2 chemical engineering students. These students have chosen to join us after completing a common first-year of engineering at UQ. Interestingly, 47% of this incoming chemical engineering cohort is female, a new record for us. It will be great to meet the students in person after a challenging year of Covid-19-imposed online tuition in 2020.

These incoming students have completed prerequisite courses of chemistry and introductory thermodynamics in their first year at UQ; however, many of them have little idea of what chemical engineering is all about or what chemical
engineers do for a living. Many students picked their new vocation because they “liked maths and chemistry at high school”. Unfortunately for us all, the vital work of chemical engineers is rarely featured on TV or in the movies.

So how can we welcome the students into our school and give them a taste of what lies ahead in their studies and their chosen profession?

The Chocolate Chip Cookie Challenge

Our answer – the Chocolate Chip Cookie Challenge! This article describes a fun exercise that we have developed in the School of Chemical Engineering. We use this exercise in the first class of CHEE2001 Process Principles, a foundation course in which students learn the fundamental principles of process engineering, including mass and energy balancing. The Chocolate Chip Cookie Challenge has three main goals:

• to start building personal connections between students which will underpin their learning and evolve into professional networks in later life;
• for students to discover the principles of chemical engineering before we teach them explicitly; and
• to illustrate how much fun chemical engineering can be.

The Chocolate Chip Cookie Challenge goes like this.

On day 1, we welcome the new students into the classroom and ask them to sit at tables of 5-6 people. First, we invite general introductions to their classmates – What is your name? Why did you choose chem eng? Where would you like to go with your degree? Then we invite them to participate in the Chocolate Chip Cookie Challenge.

The rules of the game are simple: each table of students is given six chocolate chip biscuits (40% chocolate, procured from the local Woolworths), several plastic knives, and two cups. Each team has approximately 20 minutes to “process” their choc chip biscuit feedstock to produce two streams – a valuable product of ~90% chocolate (by eye), and a byproduct of biscuit remnants. Students can use any method they like to process the feedstock, providing that they use only the equipment provided. Students must place the product and byproduct in separate cups, taking care to place all product in the two cups provided. We don’t want a large cleanup operation after the exercise!

The teachers play a minor role at this stage. During the processing, we walk around the room but try not to interfere in the group activities. We do make spot quality control inspections; if the material in the product cup does not meet the specification of 90% chocolate, we ask students to reprocess this material.

Once the 20 minutes has elapsed, we ask the students to stop processing and we move into next stage of the challenge. Each team is invited in turn to present their product and byproduct cups to the teacher, who inspects the chocolate product to ensure the material is on-spec. The teacher then weighs both the product and the byproduct cups, and records the weights. After all groups have presented their products, the teacher announces the winning team – the one with the highest weight of on-spec product – and presents the victors with a prize (a packet of lollies). Students then dispose of the products and equipment, and clean their hands (extracting chocolate from cookies can be messy on a hot, humid day in Brisbane. I recommend using refrigerated cookies).

Now, how to convert this processing activity into a simple process flow diagram? Following the cookie processing, we then ask each group to draw a simple diagram on an A4 sheet that best depicts the process or processes they used for their chocolate recovery. Note that at this stage, we have not introduced the students to the conventions of chemical engineering drawings. The students sketch a freehand drawing of what their team did (see Figures 1–3). Each group then presents their diagram to the class via the document camera and projection screens. Finally, a spokesperson for each group explains the key/novel features of their process.