Osmosis

Osmosis

Aim: To determine the concentration of cell sap in a potato cell.

Osmosis is the movement of water through a semi-permeable membrane. It starts from a weak solution and becomes a more stronger solution until the concentrations on both sides are equal.

To investigate the range of solutions needed to find the point at which the surrounding solution is the same as the cell sap in the vacuole.

0 molar - No salt

0.2 salt solution

0.4 salt solution

0.6 salt solution

0.8 salt solution

1 molar - Salt solution

Prediction

I predict that 1 molar will get lighter and 0 molar will get heavier. I think this because Osmosis is the movement of water through a semi permeable membrane. 1 molar contains most salt. So, the water will travel out of the potato cells and into the surrounding solution. Whereas 0 molar contains no salt and water will move through the semi-permeable membrane into the potato cells making the potato heavier.

In my preliminary experiment i used 0 to 3 molar, 3 molar got lighter and 0 molar got heavier.

This is a graph to show what i predict.

Apparatus

Boling tubes

Boling tube racks

A balance

Stop clock

Cork borer

Measuring cylinder

Scalpel

Tile

Potatoes

Paper towels

Diagram of experiment/apparatus.

Step by step method

1. First using the cork borer we shall carefully extract 6 pieces of potato.

2. We will then dry the pieces of potato, peel the skin off and cut the pieces in half using a scalpel. We will then imitate the smallest piece of potato and try to keep the other pieces the same size as the smallest.

3. After drying and cutting the potato to similar sizes we shall weigh the pieces using a balance ensuring each piece