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Q & A: diffusion in hot water

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Most recent answer: 03/08/2012
Q:
Why is diffusion faster through hot water?
- Codi E (age 13)
Duaringa, Queensland, Australia
A:
There are two reasons.

The first, less important, reason is simply that the diffusing molecules move faster when they're hotter.  That's very general- higher temperature always gives faster thermal motions.  This factor is about 1.37 as water heats up from 0C (273 K) to 100C (373K).

The second, more important, reason is that water gets less sticky ("viscous") as it heats up. That means that the diffusing molecules go farther before they change direction, which makes them move faster. This factor is about 6.3 as water heats up from 0C (273 K) to 100C (373K).

Mike W,

(published on 03/08/2012)

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