(2) "Another misconception that osmosis requires an attractive force," he says. "It doesn't. When water fills the bag of sugar, it's not because the sugar is pulling the water in. That's not part of the explanation."
(3) "A misconception is that osmosis always happens down a concentration gradient," he says. "When you dissolve something in water, the water doesn't necessarily get more diluted. Depending on the substance, it can get more concentrated."
(4) "Anther misconception is that you don't need to invoke a force to explain why the water flows into the bag. It's thought that, like diffusion, it's a spontaneous process," he says. "But, in fact, there is a force. It's complicated how it happens, but it turns out that the membrane or the bag, in the familiar lab demonstration exerts a force that pushes the water in."
"These misconceptions are surprisingly robust," says Kramer. "Nearly all have been discussed by other authors during the long history of osmotic research, and yet they continue to find believers in each generation of professionals. While authors in physics and biophysics have generally settled on the correct understanding of osmosis, these ideas have not penetrated into the fields of chemistry and biology. It's very surprising that, in 60 years, no physicist talked to a chemist long enough to figure this out."
|Contact: Eric Kramer|
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