Summary: Students will experiment to create three different mixtures (one of which is cornstarch an water), and test the mixtures for their efficacy as a bio-armor. Then, they will play the role of a material-science engineer to design a vest or suit of armor, based upon the results of their lab. DETAILS BELOW:
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Like this lab? Click below to see a NGSS lab on the properties of water that requires students to work together to figure out which liquid is the antidote to a venomous hornet sting. My students love the lab!
Buy the lab here: Using the Properties of Water to Find an Antidote to a Hornet's Venom
Click below to see a NGSS lab in which students design and experiment to test the stability of egg protein, and relate it to the importance of homeostasis.
Buy the lab here: Proteins and Homeostasis; Designing an Experiment
A. NEXT GENERATION SCIENCE STANDARDS HEREIN
DCI’s: PS1: Matter and Its Interactions
LS1.A: Structure and Function
ETS1: Engineering Design
ETS2: Engineering, Technology, Science, and Society
Cross Cutting Concepts: Scale, Proportion, and Quantity, Cause and Effect
Scientific and Engineering Practices:
Asking Questions and Defining Problems
Planning and Carrying Out Investigations
Constructing Explanations and Designing Solutions
Engaging in Argument from Evidence
B. SUGGESTED USES
Prior Knowledge: No specific prior knowledge is required for this lab. It can fit into a unit on states of matter, organic chemistry, or technology/material science.
Implementing the Lesson:
Materials and Setup: As long as cornstarch is one of the powders students receive, the other two can be any powders available (sugar, potato starch, salt, baking powder, sand). Cornstarch will behave like a bio-armor (non-newtonian fluid).
Materials (per pair, or lab table; it is up to you):
1. 100 grams potato starch (can be substituted, and amount can vary). (You might label it powder A)
2. 200+ grams of cornstarch (you can label it powder B). (It is about a can of coke in volume)
3. 100 grams of sucrose (can be substituted for whatever you might have). You might label it powder C.
4. Water source
5. Either a Gram scale (triple beam balance, or electronic balance)
Students could measure volumes if gram scale is not available; or allow students to use both, and have them choose how to express their quantities
6. Shallow bowls, (I use those rectangular reusable food containers)
7. Materials to test the mixtures as an armor (suggestions: I have given them metal stir rods, wooden balls from the atomic modeling kits we have in my school, students collected and used rocks, a hammer, a gentle hit/punch. Many objects will do.
My students love this lab. If yours liked it, there are more like this at my TpT store:
Tips: The ideal ratio of cornstarch to water should be between 1.5:1 to 2:1. In other words, about 1.5 cups of cornstarch to 1 cup of water up to 2:1.
Some students put something delicate (CD Case, piece of chocolate) in the bottom of their mixture, or even underneath the container to test the mixture's ability to moderate the impact.
You might expand the last part (the sketch of the design) into a poster. I have hung larger sketches up around the room, and students/admin are very interested in learning about what the lab was about.
Regarding the design of the vest/suit: Many students have creating a vest with small compartments (think bubble-wrap) in order to prevent the liquid armor from collecting on the bottom.
After the lab is through; tell the students it was cornstarch. Here a few video links that show REAL WORLD applications of exactly what this lab explores.
At this point, you might go into the chemistry of what is happening (log jam model), or discuss non-Newtonian fluids, or even discuss the relationship between science, technology, engineering, and society.
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