0mL of 50% sucrose solution
- 10% sucrose solution
40mL of distilled water
10mL of sucrose solution
- 20% sucrose solution
30mL of distilled water
20mL of 50% sucrose solution
- 30% sucrose solution
20mL of distilled water
30mL of 50% sucrose solution
- 40% sucrose solution
10mL of distilled water
40mL of 50% sucrose solution
- The above sucrose solutions were produced and then 40mL of each was poured into four separate boiling tubes which were labelled 0, 1, 2, 3 and 4(representing distilled water, 10%, 20%, 30% and 40% sucrose solutions repsectively) and they were placed on a test tube rack.
- The temperature of each boiling tube was measured to make sure they were the same.
- The masses of the potato chips were measured and recorded using a balance to two decimal places, as the masses would be almost certainly identical if they were recorded to one decimal place.
- The first chip was dropped into its boiling tubes. My partner timed the experiment from the moment it was dropped.
- At exact five minute intervals, more chips were dropped into their respective boiling tubes. This time in between was needed as only one chip could be weighed at a time after thirty minutes in the solution.
- After 30 minutes, the boiling tubes would be drained and the potato chips would be placed on paper towels.
- The chips were gently dabbed with the paper towels to dry off the excess sucrose solution, as it would have affect the mass after.
- The masses and lengths were then measured and the results were recorded on a draft table.
Apparatus
- Potato
- Size 6 Core-Borer
- White Tile
- 5 100mL Measuring Cylinders
- 5 Boiling Tubes
- Balance to 2 Decimal Places
- 5 Thermometers
- Ruler
- Knife
- Test Tube Rack
- Distilled Water
- 50% Sucrose Solution
- Paper Towel
- Stopwatch
- Marker Pen
- Pipet
Diagram
Fair Testing
The sole variable I plan to change will be the concentration of the sucrose solutions, as explained before. The variables I am testing are the percentage changes in mass and length.
For accurate results:
- The same volume of sucrose solution was used in each experiment by measuring them out using separate measuring cylinders.
- The potato chips were kept at the same lengths using a ruler and a knife, and had approximately the same mass.
- The potato chips were dropped in and taken out of the solutions at the same time.
- The potato chips were cut using the same core-borer and had the same diameters.
For reliable results:
- The temperatures of the solutions were checked to be the same (25ºC) using thermometers. When a solution was found to be warmer than another, it was cooled using running tap water.
- The entire experiment was repeated and the average of the numeric results was taken as the final results.
- All the equipment was thoroughly cleaned before the experiment.
Safety
To ensure safety:
- Safety goggles were worn throughout the whole experiment.
- The sharper utensils (the core-borer and the knife) were used carefully.
- All the equipment was thoroughly cleaned before the experiment.
- No activities besides those involving he experiment were carried out in the experiment area.
Prediction
For the potato chip in 0% sucrose solution (distilled water), I predict that the mass and length will increase. The concentration of water inside the chip is lower than the concentration of water outside the chip. This is easy to see as the concentration of water in distilled water is 100%, which is higher than any amount of water concentration in any substance (except for distilled water). The potato chip, being only partly water has a lower concentration of water in it than the distilled water.
Due to osmosis, the water molecules outside the potato chip (made up of thousands of cells with selectively permeable cell membranes) will enter the potato chip cells. The cells in this chip would probably fill up with water and become turgid. This is what will cause an increase in mass and length.
For the potato chip in 40% sucrose solution, I predict that the mass and length will decrease. The concentration of water in the sucrose solution is very low. The concentration of water in the potato cells is definitely higher.
Oppositely to the above specimen in distilled water, due to osmosis, the water molecules inside the chip cells will move out of the potato chip, through the selectively permeable cell membranes, into the sucrose solution. The cytoplasm inside the cells will shrink as they lose water and cells will be plasmolysed. This will cause the decrease in mass and length of the potato chip.
As for the remaining three sucrose solution specimens (10%, 20% and 30% sucrose solutions), I am completely unsure on what the results will be. The results however, should be able to give us a rough idea of the original concentration of water in the potato cells.
Raw Data
Draft Table of Results
Tables of Results
First Test
Second Test
Average of Two Tests
I used the following formulas to build the tables above on Microsoft Excel:
- Change in Mass = Mass After – Mass Before
- Change in Length = Length After – Length Before
- % Change in Mass = (Change in Mass x 100) ÷ Mass Before
- % Change in Length = (Change in Length x 100) ÷ Length Before
Graph of % Changes in Mass and Length vs. % Concentration of Sucrose Solution
CONCLUSION
What happened:
As I predicted, the specimen which was left in distilled water had an increase in both mass and length. The specimen which was left in the 40% sucrose solution, also following my prediction, had a decrease in mass and length. The specimen left in 10% sucrose solution gained in mass and length as well, but not to as high a magnitude as that of the specimen in distilled water. Reflectively, the specimen left in 30% sucrose solution had a decrease in mass, but not as high a magnitude as that of the specimen in 40% sucrose solution. The specimen in 20% sucrose solution decreased in mass, but apparently there was no effect on its length. I believe that there was a negative change in length, but the value was too small to record to one decimal place. The case is the same with the specimen left in 30% sucrose solution
The graph produced above shows that the lines of percentage changes in mass and length are curved. If the 20% and 30% solutions were more accurate, the line of percentage change in length would have intersected the x axis at a closer point to the intersection of the line of percentage change in mass and the x axis (approximately 16%).
Why it happened:
For the specimens in Distilled Water and 10% Sucrose Solution, the water potential on the outside of the potato chips was higher than that inside them. The potato cells went through endosmosis and water moved through the fully permeable cell walls, then through the selectively permeable cell membranes, into the potato chip cell vacuole, causing it to expand and push against the cytoplasm. This in turn made the cells turgid, and increased their size and mass by a miniscule amount. However, as there are so many cells in a chip, the chip gained a substantial increase in mass and length.
For the remaining three specimens in 20%, 30% and 40% sucrose solutions, water left the cell by exosmosis. This occurred because the water potential outside the chip was lower than that inside the chip. Water left the cell vacuole into the solution to evenly spread out. The vacuole shrunk and pulled the cytoplasm away from the cell wall. The cells plasmolysed, and each cell decreased in mass and size by a miniscule amount. Again, however as there are so many cells in a chip, the chip gained a substantial decrease in mass and length.
In approximately 16% sucrose solution, the potato chip would not have decreased nor increased in length or mass. This will be because the water potential inside the cell will be the same as the water potential outside the cell. Therefore, I can conclude that my results from this investigation also shows that the concentration of non-water substances in potato chips is approximately 16%
This is a relatively reliable investigation. Everything was measured, weighed and timed to the best of my abilities. However, it was not without faults. First of all, we noticed that during the thirty minutes, some potato chips would float while others sunk. This varied the solution pressure on the chip. We did not wish to push the chips down, as we were sure that they would float back up, and also it would have slightly stirred the solution, When we wished to change the temperature of the reaction, we ran the bottom of the tube in running tap water. This stirred the mixture, and not all the temperatures could have been kept exactly the same.
With the potato chips, the original masses differed by a large amount. The effect of this however, was reduced by calculating the percentage change in mass and not using the final mass. One of the most troublesome values in this experiment was the length of the potato chip. As we measured it to the nearest millimetre, the most change we could get was about eight percent. Also sometimes, after the testing, one side of the chip would be larger than the other side, causing confusion on which side to measure.
Lastly, as we kept a small time interval between draining each boiling tube, the times could have been dissimilar between the five specimens by an uncertainty of approximately ±5 seconds. Nevertheless, This should not have affected the results by much. There are no distinguishable anomalies I have found in the results.
Overall, I find that this investigation is accurate enough to be able to rely on. If one was to do further work on osmosis, I would recommend repeating the experiment using a smaller core borer, more solution, a range of solutions from 10% to 20% sucrose and to heat the boiling tubes to the same temperature. This should give a more accurate and in depth look to what the concentration of non-water substances in potato chips is.