In this 21-day unit, students are introduced to the anchoring phenomenon—a flameless heater in a Meal, Ready-to-Eat (MRE) that provides hot food to people by just adding water. Students explore the inside of an MRE flameless heater, then do investigations to collect evidence to support the idea that this heater and another type of flameless heater are undergoing chemical reactions as they get warm. Students have an opportunity to reflect on the engineering design process, defining stakeholders, and refining the criteria and constraints for the design solution.

This unit is part of the OpenSciEd core instructional materials for middle school.

Oh, no! I’ve dropped my phone! Most of us have experienced the panic of watching our phones slip out of our hands and fall to the floor. We’ve experienced the relief of picking up an undamaged phone and the frustration of the shattered screen. This common experience anchors learning in the Contact Forces unit as students explore a variety of phenomena to figure out, “Why do things sometimes get damaged when they hit each other?”

Student questions about the factors that result in a shattered cell phone screen lead them to investigate what is really happening to any object during a collision. They make their thinking visible with free-body diagrams, mathematical models, and system models to explain the effects of relative forces, mass, speed, and energy in collisions. Students then use what they have learned about collisions to engineer something that will protect a fragile object from damage in a collision. They investigate which materials to use, gather design input from stakeholders to refine the criteria and constraints, develop micro and macro models of how their solution is working, and optimize their solution based on data from investigations. Finally, students apply what they have learned from the investigation and design to a related design problem.

As an introduction to bioengineering, student teams are given the engineering challenge to design and build prototype artificial limbs using a simple syringe system and limited resources. As part of a NASA lunar mission scenario, they determine which substance, water (liquid) or air (gas), makes the appendages more efficient.

Students learn about material properties, and that engineers must consider many different materials properties when designing. This activity focuses on strength-to-weight ratios and how sometimes the strongest material is not always the best material.

In this math activity, students conduct a strength test using modeling clay, creating their own stress vs. strain graphs, which they compare to typical steel and concrete graphs. They learn the difference between brittle and ductile materials and how understanding the strength of materials, especially steel and concrete, is important for engineers who design bridges and structures.

Bridges come in a wide variety of sizes, shapes, and lengths and are found all over the world. It is important that bridges are strong so they are safe to cross. Design and build a your own model bridge. Test your bridge for strength using a force sensor that measures how hard you pull on your bridge. By observing a graph of the force, determine the amount of force needed to make your bridge collapse.

Construct and measure the energy efficiency and solar heat gain of a cardboard model house. Use a light bulb heater to imitate a real furnace and a temperature sensor to monitor and regulate the internal temperature of the house. Use a bright bulb in a gooseneck lamp to model sunlight at different times of the year, and test the effectiveness of windows for passive solar heating.

Earthquakes happen when forces in the Earth cause violent shaking of the ground. Earthquakes can be very destructive to buildings and other man-made structures. Design and build various types of buildings, then test your buildings for earthquake resistance using a shake table and a force sensor that measures how hard a force pushes or pulls your building.

The unit focuses on the question How can people help end pandemics? It is designed to teach students about the COVID-19 pandemic, transmission of the COVID-19 virus, and the impacts of the pandemic on communities. Over the course of the unit, students will study the COVID-19 pandemic in light of historical pandemics to build an understanding of the following key concepts:

• How the COVID-19 virus spreads from person to person and through communities,
• How strategies to reduce transmission of COVID-19 work,
• How the actions of individuals can help to end pandemics.

The unit also supports the development of two social emotional competencies: self awareness and social awareness.

After completing the associated lesson and its first associated activity, students are familiar with the 20 major bones in the human body knowing their locations and relative densities. When those bones break, lose their densities or are destroyed, we look to biomedical engineers to provide replacements. In this activity, student pairs are challenged to choose materials and create prototypes that could replace specific bones. They follow the steps of the engineering design process, researching, brainstorming, prototyping and testing to find bone replacement solutions. Specifically, they focus on identifying substances that when combined into a creative design might provide the same density (and thus strength and support) as their natural counterparts. After iterations to improve their designs, they present their bone alternative solutions to the rest of the class. They refer to the measured and calculated densities for fabricated human bones calculated in the previous activity, and conduct Internet research to learn the densities of given fabrication materials (or measure/calculate those densities if not found online).

The final activity of this unit, which integrates the Keepers of the Gate unit through the Go Public challenge, involves students taking part in experimental design. They design a lab that answers the challenge question: "You are spending the night with your grandmother when your throat starts to feel sore. Your grandma tells you to gargle with salt water and it will feel much better. Thinking this is an old wive's tale, you scoff, but when you try it later that night it works! Why?" Students must have their plan approved by the instructor before they begin. A formal lab write-up is due as part of the laboratory investigation.

Students become familiar with the engineering design process as they design, build and test chair prototypes. The miniature chairs must be sturdy and functional enough to hold a wooden, hinged artist model or a floppy stuffed animal. They use their prototypes to assess design strengths and weaknesses.

Students use a small quantity of modeling clay to make boats that float in a tub of water. The object is to build boats that hold as much weight as possible without sinking. In the process of designing and testing their prototype creations, students discover some of the basic principles of boat design, gain first-hand experience with concepts such as buoyancy and density, and experience the steps of the engineering design process.

Engineers design methods of removing particulate matter from industrial sources to minimize negative effects of air pollution. In this activity, students will undertake a similar engineering challenge as they design and build a filter to remove pepper from an air stream without blocking more than 50% of the air.

Following the steps of the engineering design process and acting as biomedical engineers, student teams use everyday materials to design and develop devices and approaches to unclog blood vessels. Through this open-ended design project, they learn about the circulatory system, biomedical engineering, and conditions that lead to heart attacks and strokes.

Students will build and test composite materials to determine if they increase strength without significantly increasing weight.

Students teams design and build shoe prototypes that convert between high heels and athletic shoes. They apply their knowledge about the mechanics of walking and running as well as shoe design (as learned in the associated lesson) to design a multifunctional shoe that is both fashionable and functional.

Student groups are given a set of materials: cardboard, insulating materials, aluminum foil and Plexiglas, and challenged to build solar ovens. The ovens must collect and store as much of the sun's energy as possible. Students experiment with heat transfer through conduction by how well the oven is insulated and radiation by how well it absorbs solar radiation. They test the effectiveness of their designs qualitatively by baking something and quantitatively by taking periodic temperature measurements and plotting temperature vs. time graphs. To conclude, students think like engineers and analyze the solar oven's strengths and weaknesses compared to conventional ovens.

Students learn about the role engineers and mathematicians play in developing the perfect bungee cord length by simulating and experimenting with bungee jumping using washers and rubber bands. Working as if they are engineers for a (hypothetical) amusement park, students are challenged to develop a show-stopping bungee jumping ride that is safe. To do this, they must find the maximum length of the bungee cord that permits jumpers (such as brave Washy!) to get as close to the ground as possible without going "splat"! This requires them to learn about force and displacement and run an experiment. Student teams collect and plot displacement data and calculate the slope, linear equation of the line of best fit and spring constant using Hooke's law. Students make hypotheses, interpret scatter plots looking for correlations, and consider possible sources of error. An activity worksheet, pre/post quizzes and a PowerPoint® presentation are included.

Students design and build model landfills using materials similar to those used by engineers for full-scale landfills. Their completed small-size landfills are "rained" on and subjected to other erosion processes. The goal is to create landfills that hold the most garbage, minimize the cost to build and keep trash and contaminated water inside the landfill to prevent it from causing environmental damage. Teams create designs within given budgets, test the landfills' performance, and graph and compare designs for capacity, cost and performance.