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Water potential

This whole terminology is confusing.
Negative water potential
Lower negative water potential
Higher water potential

Distilled water is 0
So lets say a solution has a water potential of -10. Thats a negative water potential... So now i have a second solution with a water potential of -20, is that a higher or lower negative solution? I would say its a lower negative water potential as its further from 0 but am i thinking of it in the wrong way and its actually a higher negative water potential as its further from 0?

I know water goes from -20 to -10 for example but i'm not sure whether i am meant to say water moves from a higher negative water potential to a lower negative water potential vice-versa or is it just lower water potential to higher water potential? :s-smilie:
Reply 1
Avatar for A.J.B
A.J.B
look man, think of it this way, a beaker full of pure water only has water molecules in it, nothing else, so thats a water potential of zero, when, say, i add a teaspoon of sugar to this beaker of water, the beaker now has water and sugar molecules, so water molecules make up 90% of whats in the beaker giving a water potential of -10, which is pretty close to zero, when say i add another teaspoon of sugar, the water potential falls to -20 and vise versa, the closer the value is to zero, the higher the water potential.
Reply 2
Avatar for Tagit
Tagit
OP
12
I know why it becomes -10, -20 etc. I just want to know whats called what

I know distilled water has a higher water potential than -10, which has a higher water potential than -20.

So does that mean distilled water has a higher negative water potential or a lower negative water potential than the -10 solution. Basically if i am using the word negative how does it change?
Reply 3
Avatar for A.J.B
A.J.B
distilled water has a higher water potential, u would say water would diffuse from an area of high water potential to an area of low water potential, ignore negatives its just an indication, like exothermic and endothermic (if u know wat i mean)
Reply 4
Avatar for x.beth.x
x.beth.x
11
Water molecules move from a high water potential to a low water potential. They wouldn't move from a low water potential to a high water potential as that is against the water potential gradient.

I thought a negative water potential just meant to water potential wasn't 0KPa i.e. therefore the solution contains solutes, it isn't pure water.

Then high water potential and low water potential are just relative terms. A solution with a high water potential contains a relatively high amount of water molecules to solute molecules whilst a solution with a low water potential contains a relatively low amount of water molecules and more solute molecules.
Reply 5
Avatar for Tagit
Tagit
OP
12
Thanks.

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