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Descripción
Mapa Mental por Flo Sumpter, actualizado hace más de 1 año
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Creado por Flo Sumpter
hace más de 3 años
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B1 cells - osmosis
- DEFINITON - osmosis is the movement of water molecules across a partially
permeable membrane from a region of higher water concentration to a region of
lower water concentration.
- osmosis is a special case of diffusion
- a partially permeable membrane is just one very small holes
in it. So small, only tiny molecules can pass through them
and bigger molecules can't
- the water molecules actually pass both ways through the
membrane during osmosis. This happens because water
molecules move about randomly all the time.
- but because there are more water
molecules on one side than on the other,
there's a steady net flow of water into the
region with fewer water molecules
- this means the strong sugar solutions get more
dilute. the water acts like it's trying to 'even up' the
concentration either side of the membrane
- this means the strong sugar solutions get more
dilute. the water acts like it's trying to 'even up' the
concentration either side of the membrane
- a partially permeable membrane is just one very small holes
in it. So small, only tiny molecules can pass through them
and bigger molecules can't
- you can observe the effect of sugar solutions on plant tissue - PRATICAL
- 1. You cut up a potato into identical cylinders, and get some beakers with different sugar
solutions in them. one should be pure water and another should be a very concentrated sugar
solutions, then you can have a few others with concentrations in between
- 2. measure the mass of the cylinders, then leave one cylinder in each beaker for 24 hours or so.
- 3. then take them out, dry them with a paper towel and measure their masses again
- 4. If the cylinders have drawn in water by osmosis, they'll have increased in mass. if water has been
drawn out, they'll have decreased in mass. you can calculate the percentage change in mass then plot
a few graphs and things.
- 5. the dependent variable is the potato mass and the independent variable is the
concentration of the sugar solution. ALL other variables must be kept the same in each
case or the experiment won't be a fair test
- 6. you need to be aware of the errors that may arise. sometimes they may occur when carrying
out the method e.g if some potato cylinders weren't fully dried, the excess water would give a
higher mass or if water evaporated from the beakers, the concentrations of the sugar solutions
would change.
- you can reduce the effect of these errors
by repeating the experiment and
calculating a mean percentage change at
each concentration
- you can reduce the effect of these errors
by repeating the experiment and
calculating a mean percentage change at
each concentration
- 6. you need to be aware of the errors that may arise. sometimes they may occur when carrying
out the method e.g if some potato cylinders weren't fully dried, the excess water would give a
higher mass or if water evaporated from the beakers, the concentrations of the sugar solutions
would change.
- 5. the dependent variable is the potato mass and the independent variable is the
concentration of the sugar solution. ALL other variables must be kept the same in each
case or the experiment won't be a fair test
- 4. If the cylinders have drawn in water by osmosis, they'll have increased in mass. if water has been
drawn out, they'll have decreased in mass. you can calculate the percentage change in mass then plot
a few graphs and things.
- 3. then take them out, dry them with a paper towel and measure their masses again
- 2. measure the mass of the cylinders, then leave one cylinder in each beaker for 24 hours or so.
- 1. You cut up a potato into identical cylinders, and get some beakers with different sugar
solutions in them. one should be pure water and another should be a very concentrated sugar
solutions, then you can have a few others with concentrations in between
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