Finding out the affect of different concentrations of sucrose solution

Finding out the affect of different concentrations of sucrose solution

on the mass of potato chips

Introduction

The aim of this investigation is to see when osmosis occurs in potato

cells and whether anything happens to them when they are put in

different concentrations of sucrose solution. I have to apply my

background knowledge to devise an experiment which will tell me

whether if different concentrations of water molecules in a solution

will affect the mass of plant cell when they are put into it.

Background knowledge

Osmosis is like diffusion but only of water molecules and it only

happens when there are different concentrations of water molecules on

either side of a selectively permeable membrane.

The selectively permeable membrane "gaps" are only small enough to let

water molecules pass through and not big molecules such as sucrose

molecules.

Water molecules from each side of the membrane always pass to the

other side. When one side of the selectively permeable membrane has a

higher concentration of water molecules than the other, more water

molecules from the side containing a higher concentration of water

molecules will pass through to the side with a lower concentration of

water molecules. Less water molecules from the side with a lower water

molecule concentration will pass to the other side because there are

less of them.

If the concentration of water molecules on either side of the

selectively membrane is the same then the net flow of water in either

direction will be the same. This results in no net flow of

water-osmosis.

An example of osmosis happening in a plant cell is when a potato chip

is put into distilled water. The cell membrane of the potato cells is

the selectively permeable membrane between the concentration of water

molecules inside the potato cells and the distilled water that is

outside of the potato cells. As the concentration of water molecules

is of a higher concentration in the distilled water than inside the

potato, there are more water molecules going through the potato

membrane into the cell than water molecules from the inside of the

potato going through to the other side.

This is because there are more water molecules in the distilled water.

Therefore the net flow of water by osmosis is into the potato cells.

As more water molecules pass into the potato cells, the va...

... middle of paper ...

...Maybe next time I could roll each potato chip down the

paper towel once and blot the ends of them two times on the paper

towel.

To prove that my prediction is correct in any osmosis experiment, I

could do another experiment, which shows osmosis happening and why it

happens-different concentrations between a selectively permeable

membrane. The experiment is shown below:

Apparatus

* 20cm in length visking tubing.

* 20cm3 water

* 10cm3 plastic syringe

* testing tube

Method

Tie a knot at the end of 20cm length visking tube that has been soaked

in water. Put 3cm3 of strong sugar solution in the plastic syringe and

use that to partly fill the visking tube-it should be floppy. Place

the visking tubing into a test tube containing water 20cm3 . Leave the

visking tubing in the test tube for about 30-45 minutes.

You should record your observations of the visking tubing before it

was put into the test tube of water and after it had been left in the

water. Look for any changes in how it looks and feels. Is it turgid or

flaccid?

References

Collins GCSE total revision Science by Mike Smith and Chris Sunley

GCSE Biology second edition by D.G. Mackean