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Name: Rigela
Status: Educator
Grade: 9-12
Location: N/A
Country: N/A
Date: July 2005


Question:
What are some simple experiments involving diffusion which explore the theories and concepts surrounding the surface area to volume ratio?



Replies:
This took some thought. I don't know the answer to the proposed experiments. Fill various size balloons rubber -- not aluminized -- with helium gas. You can measure the internal pressure with a simple pressure gauge, the volume (assume a sphere so: V= 4/3*pi*R^3 and surface area S= 4*pi*R^2. Then follow the decrease in volume and surface area as the helium diffuses through the rubber. It only takes a few days. The pressure can be related to the volume and surface area by monitoring the pressure as you blow the balloons up. You can determine "V" and "S" by measuring the circumference of the balloon C= 2*pi*R vs. time. This gives you "V", "S", and "P" as a function of time, size and pressure. Use different size baloons.

Vince Calder



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