Elizabeth Shen
8th Grade, Stoller Middle School
Portland, OR
Elizabeth figured out a low-cost way to test water’s diffusivity, or how fast it spreads.
Diffusion-Only Water Transport and How to Modulate Its Speed
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Project Background
Oil pollution is a big problem. Removing it from water is vital for the environment, Elizabeth says. “I believe physical absorption is the quickest and most cost-effective method,” she notes “And the core of absorption is diffusion.” Diffusion occurs when molecules spread out, moving from an area highly concentrated with molecules to an area with a lower concentration. Elizabeth came up with a low-cost method to determine water’s rate of diffusion, or diffusivity.
Tactics and Results
Elizabeth designed an apparatus that holds a single paper towel by the edges so that it’s flat and parallel to the ground. That way she could measure how water spread across the paper towel without gravity interfering. Elizabeth let water seep into the paper towel from one end and measured how far the waterline traveled at various time points. She repeated the process with water at different temperatures. By adapting an equation that calculates heat transfer, Elizabeth figured out the water’s diffusivity. As temperature increased, so did diffusivity. Figuring out how water moved from one side of the paper towel to the other also helped her design different paper towel shapes that changed water’s diffusion speed. A tall, thin hourglass-like shape increased speed, Elizabeth says. But a shape with a larger center and narrower ends reduced speed. “Knowing diffusivity can help predict the movement of substances through a material and identify material properties,” she says.
Beyond the Project
In the future, Elizabeth would like to code a computer program that can simulate water’s diffusion in more complex 2-D and 3-D environments.
Other interests
Elizabeth enjoys playing piano and violin, writing and the board game Go. She would like to become a neurosurgeon and neuroscientist because she’s fascinated by the brain. “I have often wondered how one organ can enable such thoughts, emotions and creativity,” she says.
