osmosis

Planning

Osmosis is when water passes from a area of high water concentration (a dilute solution) through a semi-permeable membrane to an area of low water concentration (a concentrated solution). According to 'Encarta Encyclopaedia 97´, osmosis is "the flow of water by diffusion through a differentially permeable membrane from areas of high water concentration to regions of low water concentration." The diagram below illustrates this:

The aim of this experiment is to investigate the movement of water into and out of plant cells by osmosis. The cells chosen for study will be taken from potato strips as they provide a ready supply of uniform material.

All plant cell membranes are differentially permeable, which means that they will allow some substances to penetrate them but not others. Water can freely penetrate all membranes. The cellulose cell wall does not act as a differentially permeable membrane and will allow most substances that are dissolved in water to freely pass t...