Investigating the Water Potential of a Potato

Topics: Osmosis, Concentration, Potato, Water, Mass, Semipermeable membrane / Pages: 12 (2991 words) / Published: Feb 10th, 2007
Investigating the water potential of a potato


Osmosis is the movement of water molecules from a region of high water concentration to a low water concentration through a semi-permeable membrane. Our aim is to investigate the water potential of a potato through osmosis, by finding the difference in weight before and after the potato has been set in a solution of water, sugar or salt.

Trial Method

Firstly we collected the equipment. This included a scalpel, potato cutter, and test tubes. Then we cut the potato using the potato cutter into cylinders. Then we used the scalpel to cut each potato strip down to size. To get each strip as close as possible the same length and width we used a ruler get correct measurements. Then we filled one test tube with distilled water and another 5 with different sugar solutions in increasing strength of molar, starting with 0.2 molar. After that we dropped our potato strips into each test tube at the same time and let them sit for 28 hours and 30 minutes. We poured the solutions out to get the potato strips. Then we carried them one by one over to the scales. We then weighed them to see if they had gained or lost weight. Once we had the results we calculated the percentage weight gained or lost.

Risk Assessment

Make sure all bags are out of the way
Make sure books are not obstructing the experiment
Tuck in ties
Do not sit down
Carry knives with the head facing downwards
Tie back long hair
Wash hands after handling potatoes or equipment

Trail Apparatus List

Test tubes x6
Test racks x1
Potatoes x2
Cylinder cutters x1
Crafting knives x1
Ruler x1
Weighing machine

Variables To Control

There are several variables to control including volume of water. Firstly the volume of water needs to be kept constant to allow a fair test amongst all the potato strips because different amounts of water will determine how much of it will osmosize into or out of the

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