I love using engineering challenges with my middle school science students. Not only does it reinforce critical thinking and problem-solving skills, it gives them an opportunity to be creative and to explore concepts through experimentation. One of my favorite engineering challenges is the Magical Moving Rice Challenge, an activity we engage in as we prepare to learn how sound travels through the ear to the brain.
The Magical Moving Rice Challenge is a fantastic sound stem activity that doesn’t require a lot of materials. Students are given a cup, some plastic wrap, rubber bands, and a few grains of rice (usually inside a second, smaller cup). They also have access to scissors, but are told the scissors cannot be a part of whatever they create. The challenge is to design a contraption, using only the materials given, that will cause the rice to move, pop, or jump. However, they have to work within a few constraints. They cannot touch the rice in anyway, nor can they blow on it, and they can’t touch anything that is touching the rice (in other words, they can’t touch the contraption itself).
A few simple materials leads to an exciting engineering challenge about sound and how the ear works.
The Engineering Process – This poster reminds us of the cyclical nature of the engineering process and the steps we should take as we work through it.
When I’m doing this activity with my students, I make sure to have plenty of extra materials on hand so they can try and try again. As part of the engineering process, I want them to test and improve their contraption. But we also brainstorm, sketch, talk to one another and explore different ideas. Typically, students gravitate towards some version of shaking the cup, either with the rice inside the cup, or the rice on top of the plastic wrap stretched across the cup. The shaking usually means they are touching the contraption in some way so I follow up with questions like: “Is there a way to shake the cup without touching it?” “Are there forces around us that can cause movement that we might not always see?” “You can’t blow on the rice or cup, but is there another way to move the air around the contraption?”
The goal with the challenge is for students to figure out that they can move the rice using sound waves. However, students will engineer several creative ways to meet the challenge within the constraints- and that’s great! Part of why I choose to use this activity, rather than having all my students build the same model of an ear (like I do with the lung model), is because it opens up their creativity and gives each of them an opportunity to shine and meet the challenge in a way that is accessible for them. Some creative designs I’ve seen include shooting the rubber band at the cup holding the rice (I think the students just really enjoyed this one) and an incredibly clever design that would best be described as a self-launching catapult (it was quite cool!). But nearly always there is at least one group of students in each of the science classes that produces something that models the workings of our ear. We use our discussion about all the engineering feats, and these “ear models” in particular, to begin our work learning the parts of the ear and their functions.
This lesson is part of a bigger unit about how our sensory receptors respond to stimuli and send messages to our brain for processing. In this lesson, we are concentrating on our sound receptors located in the ear, and our sense of hearing. The sense of hearing allows us to interpret sound waves created by moving air. As student learn about how the ear works in this lesson, they discover that the ear is specially designed to trap incoming sound waves, funnel them to the middle ear, and convert them into electric impulses that can be interpreted by the brain. The incoming sound waves bounce against the ear drum, a thin membrane stretched across the end of the ear canal, which sets off a series of vibrations in the inner ear, all leading to the sensory receptors. A piece of plastic wrap stretched tightly across a cup and secured with a rubber band can simulate the ear drum. Rice grains placed on the top of the plastic wrap will jump, hop and move when loud sounds emanate near the cup due to movement of air caused by the sound waves. From this, students get an up-close look at how sound waves effect their ear drums and start the process of hearing sound.