Osmosis Lab Report

Essay by jessharp1 November 2004

Introduction

The purpose of this experiment was to demonstrate osmosis. Osmosis is the diffusion of water across a selectively permeable membrane (Bell et al 2004). Osmosis is the movement of water molecules from an area of high concentration to an area of low concentration (Brown 1999). Hypertonic is the solution with a higher salt concentration. Hypotonic solution is the solution with the lower salt concentration. My hypothesis is that the potato core will increase in size. When the solution is hypertonic, the potato will decrease in size making the potato hypotonic. Osmosis is really interesting, that is why I chose to write this report about it.

Materials and Methods

We first cut out six cores out of a potato. We trimmed them all to the same length using a razor. After we had cut them to the same size we weighed them using a scale. The weight ranged from .692g

to .732g. As the potatoes were being trimmed and weighed, I prepared five various solutions of salt water. When the potatoes and water we both prepared, we put the potatoes in the salt water and allowed them to soak for 45 minutes. After the time expired we extracted the cores from the water. Once again we measured the length and weight.

Results

In first three test tubes, the potato core became shorter and was lighter than the original (see attached table and graphs). The length changed from 2mm to 1mm and the weight changed from .19g to .14g. In test tube four, the potato core remained the same length of 28 mm, but was heavier than the original by .012g (see attached table and graphs). In test tubes five and six, the potato core increased in size by 1mm and 2mm and is heavier by .122g to .183g than the original (see attached table and graphs).

Discussion

My hypothesis was that the potato core will increase in size when it is hypertonic to the salt solution. I also predicted the potato will decrease in size when it is hypotonic. My results showed that when the solution contained a higher percentage salt than the potato, the potato got smaller, displayed in the first three test tubes. Test tube four displayed that when the solution is similar to the potato not much change takes place in the core. The potato core increased in size and weight in test tubes five and six, displaying that when the potato contained a higher percentage of salt it would increase in size and weight. I would like to test other fruits and vegetables in salt solutions, to test its salt presence.

References

Bell, Rebekah P., et al. Investigations in Biology 121. Chattanooga: University of Tennessee at Chattanooga, 2004